1 // SPDX-License-Identifier: GPL-2.0-only
5 * Runtime locking correctness validator
7 * Started by Ingo Molnar:
9 * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
10 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
12 * this code maps all the lock dependencies as they occur in a live kernel
13 * and will warn about the following classes of locking bugs:
15 * - lock inversion scenarios
16 * - circular lock dependencies
17 * - hardirq/softirq safe/unsafe locking bugs
19 * Bugs are reported even if the current locking scenario does not cause
20 * any deadlock at this point.
22 * I.e. if anytime in the past two locks were taken in a different order,
23 * even if it happened for another task, even if those were different
24 * locks (but of the same class as this lock), this code will detect it.
26 * Thanks to Arjan van de Ven for coming up with the initial idea of
27 * mapping lock dependencies runtime.
29 #define DISABLE_BRANCH_PROFILING
30 #include <linux/mutex.h>
31 #include <linux/sched.h>
32 #include <linux/sched/clock.h>
33 #include <linux/sched/task.h>
34 #include <linux/sched/mm.h>
35 #include <linux/delay.h>
36 #include <linux/module.h>
37 #include <linux/proc_fs.h>
38 #include <linux/seq_file.h>
39 #include <linux/spinlock.h>
40 #include <linux/kallsyms.h>
41 #include <linux/interrupt.h>
42 #include <linux/stacktrace.h>
43 #include <linux/debug_locks.h>
44 #include <linux/irqflags.h>
45 #include <linux/utsname.h>
46 #include <linux/hash.h>
47 #include <linux/ftrace.h>
48 #include <linux/stringify.h>
49 #include <linux/bitmap.h>
50 #include <linux/bitops.h>
51 #include <linux/gfp.h>
52 #include <linux/random.h>
53 #include <linux/jhash.h>
54 #include <linux/nmi.h>
55 #include <linux/rcupdate.h>
56 #include <linux/kprobes.h>
57 #include <linux/lockdep.h>
58 #include <linux/context_tracking.h>
60 #include <asm/sections.h>
62 #include "lockdep_internals.h"
64 #include <trace/events/lock.h>
66 #ifdef CONFIG_PROVE_LOCKING
67 static int prove_locking = 1;
68 module_param(prove_locking, int, 0644);
70 #define prove_locking 0
73 #ifdef CONFIG_LOCK_STAT
74 static int lock_stat = 1;
75 module_param(lock_stat, int, 0644);
81 static struct ctl_table kern_lockdep_table[] = {
82 #ifdef CONFIG_PROVE_LOCKING
84 .procname = "prove_locking",
85 .data = &prove_locking,
86 .maxlen = sizeof(int),
88 .proc_handler = proc_dointvec,
90 #endif /* CONFIG_PROVE_LOCKING */
91 #ifdef CONFIG_LOCK_STAT
93 .procname = "lock_stat",
95 .maxlen = sizeof(int),
97 .proc_handler = proc_dointvec,
99 #endif /* CONFIG_LOCK_STAT */
103 static __init int kernel_lockdep_sysctls_init(void)
105 register_sysctl_init("kernel", kern_lockdep_table);
108 late_initcall(kernel_lockdep_sysctls_init);
109 #endif /* CONFIG_SYSCTL */
111 DEFINE_PER_CPU(unsigned int, lockdep_recursion);
112 EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);
114 static __always_inline bool lockdep_enabled(void)
119 if (this_cpu_read(lockdep_recursion))
122 if (current->lockdep_recursion)
129 * lockdep_lock: protects the lockdep graph, the hashes and the
130 * class/list/hash allocators.
132 * This is one of the rare exceptions where it's justified
133 * to use a raw spinlock - we really dont want the spinlock
134 * code to recurse back into the lockdep code...
136 static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
137 static struct task_struct *__owner;
139 static inline void lockdep_lock(void)
141 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
143 __this_cpu_inc(lockdep_recursion);
144 arch_spin_lock(&__lock);
148 static inline void lockdep_unlock(void)
150 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
152 if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
156 arch_spin_unlock(&__lock);
157 __this_cpu_dec(lockdep_recursion);
160 static inline bool lockdep_assert_locked(void)
162 return DEBUG_LOCKS_WARN_ON(__owner != current);
165 static struct task_struct *lockdep_selftest_task_struct;
168 static int graph_lock(void)
172 * Make sure that if another CPU detected a bug while
173 * walking the graph we dont change it (while the other
174 * CPU is busy printing out stuff with the graph lock
184 static inline void graph_unlock(void)
190 * Turn lock debugging off and return with 0 if it was off already,
191 * and also release the graph lock:
193 static inline int debug_locks_off_graph_unlock(void)
195 int ret = debug_locks_off();
202 unsigned long nr_list_entries;
203 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
204 static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
207 * All data structures here are protected by the global debug_lock.
209 * nr_lock_classes is the number of elements of lock_classes[] that is
212 #define KEYHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
213 #define KEYHASH_SIZE (1UL << KEYHASH_BITS)
214 static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
215 unsigned long nr_lock_classes;
216 unsigned long nr_zapped_classes;
217 unsigned long max_lock_class_idx;
218 struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
219 DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
221 static inline struct lock_class *hlock_class(struct held_lock *hlock)
223 unsigned int class_idx = hlock->class_idx;
225 /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
228 if (!test_bit(class_idx, lock_classes_in_use)) {
230 * Someone passed in garbage, we give up.
232 DEBUG_LOCKS_WARN_ON(1);
237 * At this point, if the passed hlock->class_idx is still garbage,
238 * we just have to live with it
240 return lock_classes + class_idx;
243 #ifdef CONFIG_LOCK_STAT
244 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
246 static inline u64 lockstat_clock(void)
248 return local_clock();
251 static int lock_point(unsigned long points[], unsigned long ip)
255 for (i = 0; i < LOCKSTAT_POINTS; i++) {
256 if (points[i] == 0) {
267 static void lock_time_inc(struct lock_time *lt, u64 time)
272 if (time < lt->min || !lt->nr)
279 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
284 if (src->max > dst->max)
287 if (src->min < dst->min || !dst->nr)
290 dst->total += src->total;
294 struct lock_class_stats lock_stats(struct lock_class *class)
296 struct lock_class_stats stats;
299 memset(&stats, 0, sizeof(struct lock_class_stats));
300 for_each_possible_cpu(cpu) {
301 struct lock_class_stats *pcs =
302 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
304 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
305 stats.contention_point[i] += pcs->contention_point[i];
307 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
308 stats.contending_point[i] += pcs->contending_point[i];
310 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
311 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
313 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
314 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
316 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
317 stats.bounces[i] += pcs->bounces[i];
323 void clear_lock_stats(struct lock_class *class)
327 for_each_possible_cpu(cpu) {
328 struct lock_class_stats *cpu_stats =
329 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
331 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
333 memset(class->contention_point, 0, sizeof(class->contention_point));
334 memset(class->contending_point, 0, sizeof(class->contending_point));
337 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
339 return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
342 static void lock_release_holdtime(struct held_lock *hlock)
344 struct lock_class_stats *stats;
350 holdtime = lockstat_clock() - hlock->holdtime_stamp;
352 stats = get_lock_stats(hlock_class(hlock));
354 lock_time_inc(&stats->read_holdtime, holdtime);
356 lock_time_inc(&stats->write_holdtime, holdtime);
359 static inline void lock_release_holdtime(struct held_lock *hlock)
365 * We keep a global list of all lock classes. The list is only accessed with
366 * the lockdep spinlock lock held. free_lock_classes is a list with free
367 * elements. These elements are linked together by the lock_entry member in
370 static LIST_HEAD(all_lock_classes);
371 static LIST_HEAD(free_lock_classes);
374 * struct pending_free - information about data structures about to be freed
375 * @zapped: Head of a list with struct lock_class elements.
376 * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
377 * are about to be freed.
379 struct pending_free {
380 struct list_head zapped;
381 DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
385 * struct delayed_free - data structures used for delayed freeing
387 * A data structure for delayed freeing of data structures that may be
388 * accessed by RCU readers at the time these were freed.
390 * @rcu_head: Used to schedule an RCU callback for freeing data structures.
391 * @index: Index of @pf to which freed data structures are added.
392 * @scheduled: Whether or not an RCU callback has been scheduled.
393 * @pf: Array with information about data structures about to be freed.
395 static struct delayed_free {
396 struct rcu_head rcu_head;
399 struct pending_free pf[2];
403 * The lockdep classes are in a hash-table as well, for fast lookup:
405 #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
406 #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
407 #define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
408 #define classhashentry(key) (classhash_table + __classhashfn((key)))
410 static struct hlist_head classhash_table[CLASSHASH_SIZE];
413 * We put the lock dependency chains into a hash-table as well, to cache
416 #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
417 #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
418 #define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
419 #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
421 static struct hlist_head chainhash_table[CHAINHASH_SIZE];
424 * the id of held_lock
426 static inline u16 hlock_id(struct held_lock *hlock)
428 BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16);
430 return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));
433 static inline unsigned int chain_hlock_class_idx(u16 hlock_id)
435 return hlock_id & (MAX_LOCKDEP_KEYS - 1);
439 * The hash key of the lock dependency chains is a hash itself too:
440 * it's a hash of all locks taken up to that lock, including that lock.
441 * It's a 64-bit hash, because it's important for the keys to be
444 static inline u64 iterate_chain_key(u64 key, u32 idx)
446 u32 k0 = key, k1 = key >> 32;
448 __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
450 return k0 | (u64)k1 << 32;
453 void lockdep_init_task(struct task_struct *task)
455 task->lockdep_depth = 0; /* no locks held yet */
456 task->curr_chain_key = INITIAL_CHAIN_KEY;
457 task->lockdep_recursion = 0;
460 static __always_inline void lockdep_recursion_inc(void)
462 __this_cpu_inc(lockdep_recursion);
465 static __always_inline void lockdep_recursion_finish(void)
467 if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion)))
468 __this_cpu_write(lockdep_recursion, 0);
471 void lockdep_set_selftest_task(struct task_struct *task)
473 lockdep_selftest_task_struct = task;
477 * Debugging switches:
481 #define VERY_VERBOSE 0
484 # define HARDIRQ_VERBOSE 1
485 # define SOFTIRQ_VERBOSE 1
487 # define HARDIRQ_VERBOSE 0
488 # define SOFTIRQ_VERBOSE 0
491 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
493 * Quick filtering for interesting events:
495 static int class_filter(struct lock_class *class)
499 if (class->name_version == 1 &&
500 !strcmp(class->name, "lockname"))
502 if (class->name_version == 1 &&
503 !strcmp(class->name, "&struct->lockfield"))
506 /* Filter everything else. 1 would be to allow everything else */
511 static int verbose(struct lock_class *class)
514 return class_filter(class);
519 static void print_lockdep_off(const char *bug_msg)
521 printk(KERN_DEBUG "%s\n", bug_msg);
522 printk(KERN_DEBUG "turning off the locking correctness validator.\n");
523 #ifdef CONFIG_LOCK_STAT
524 printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
528 unsigned long nr_stack_trace_entries;
530 #ifdef CONFIG_PROVE_LOCKING
532 * struct lock_trace - single stack backtrace
533 * @hash_entry: Entry in a stack_trace_hash[] list.
534 * @hash: jhash() of @entries.
535 * @nr_entries: Number of entries in @entries.
536 * @entries: Actual stack backtrace.
539 struct hlist_node hash_entry;
542 unsigned long entries[] __aligned(sizeof(unsigned long));
544 #define LOCK_TRACE_SIZE_IN_LONGS \
545 (sizeof(struct lock_trace) / sizeof(unsigned long))
547 * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
549 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
550 static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
552 static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
554 return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
555 memcmp(t1->entries, t2->entries,
556 t1->nr_entries * sizeof(t1->entries[0])) == 0;
559 static struct lock_trace *save_trace(void)
561 struct lock_trace *trace, *t2;
562 struct hlist_head *hash_head;
566 BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
567 BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
569 trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
570 max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
571 LOCK_TRACE_SIZE_IN_LONGS;
573 if (max_entries <= 0) {
574 if (!debug_locks_off_graph_unlock())
577 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
582 trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
584 hash = jhash(trace->entries, trace->nr_entries *
585 sizeof(trace->entries[0]), 0);
587 hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
588 hlist_for_each_entry(t2, hash_head, hash_entry) {
589 if (traces_identical(trace, t2))
592 nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
593 hlist_add_head(&trace->hash_entry, hash_head);
598 /* Return the number of stack traces in the stack_trace[] array. */
599 u64 lockdep_stack_trace_count(void)
601 struct lock_trace *trace;
605 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
606 hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
614 /* Return the number of stack hash chains that have at least one stack trace. */
615 u64 lockdep_stack_hash_count(void)
620 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
621 if (!hlist_empty(&stack_trace_hash[i]))
628 unsigned int nr_hardirq_chains;
629 unsigned int nr_softirq_chains;
630 unsigned int nr_process_chains;
631 unsigned int max_lockdep_depth;
633 #ifdef CONFIG_DEBUG_LOCKDEP
635 * Various lockdep statistics:
637 DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
640 #ifdef CONFIG_PROVE_LOCKING
645 #define __USAGE(__STATE) \
646 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
647 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
648 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
649 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
651 static const char *usage_str[] =
653 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
654 #include "lockdep_states.h"
656 [LOCK_USED] = "INITIAL USE",
657 [LOCK_USED_READ] = "INITIAL READ USE",
658 /* abused as string storage for verify_lock_unused() */
659 [LOCK_USAGE_STATES] = "IN-NMI",
663 const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
665 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
668 static inline unsigned long lock_flag(enum lock_usage_bit bit)
673 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
676 * The usage character defaults to '.' (i.e., irqs disabled and not in
677 * irq context), which is the safest usage category.
682 * The order of the following usage checks matters, which will
683 * result in the outcome character as follows:
685 * - '+': irq is enabled and not in irq context
686 * - '-': in irq context and irq is disabled
687 * - '?': in irq context and irq is enabled
689 if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
691 if (class->usage_mask & lock_flag(bit))
693 } else if (class->usage_mask & lock_flag(bit))
699 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
703 #define LOCKDEP_STATE(__STATE) \
704 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
705 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
706 #include "lockdep_states.h"
712 static void __print_lock_name(struct lock_class *class)
714 char str[KSYM_NAME_LEN];
719 name = __get_key_name(class->key, str);
720 printk(KERN_CONT "%s", name);
722 printk(KERN_CONT "%s", name);
723 if (class->name_version > 1)
724 printk(KERN_CONT "#%d", class->name_version);
726 printk(KERN_CONT "/%d", class->subclass);
730 static void print_lock_name(struct lock_class *class)
732 char usage[LOCK_USAGE_CHARS];
734 get_usage_chars(class, usage);
736 printk(KERN_CONT " (");
737 __print_lock_name(class);
738 printk(KERN_CONT "){%s}-{%d:%d}", usage,
739 class->wait_type_outer ?: class->wait_type_inner,
740 class->wait_type_inner);
743 static void print_lockdep_cache(struct lockdep_map *lock)
746 char str[KSYM_NAME_LEN];
750 name = __get_key_name(lock->key->subkeys, str);
752 printk(KERN_CONT "%s", name);
755 static void print_lock(struct held_lock *hlock)
758 * We can be called locklessly through debug_show_all_locks() so be
759 * extra careful, the hlock might have been released and cleared.
761 * If this indeed happens, lets pretend it does not hurt to continue
762 * to print the lock unless the hlock class_idx does not point to a
763 * registered class. The rationale here is: since we don't attempt
764 * to distinguish whether we are in this situation, if it just
765 * happened we can't count on class_idx to tell either.
767 struct lock_class *lock = hlock_class(hlock);
770 printk(KERN_CONT "<RELEASED>\n");
774 printk(KERN_CONT "%px", hlock->instance);
775 print_lock_name(lock);
776 printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
779 static void lockdep_print_held_locks(struct task_struct *p)
781 int i, depth = READ_ONCE(p->lockdep_depth);
784 printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
786 printk("%d lock%s held by %s/%d:\n", depth,
787 depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
789 * It's not reliable to print a task's held locks if it's not sleeping
790 * and it's not the current task.
792 if (p != current && task_is_running(p))
794 for (i = 0; i < depth; i++) {
796 print_lock(p->held_locks + i);
800 static void print_kernel_ident(void)
802 printk("%s %.*s %s\n", init_utsname()->release,
803 (int)strcspn(init_utsname()->version, " "),
804 init_utsname()->version,
808 static int very_verbose(struct lock_class *class)
811 return class_filter(class);
817 * Is this the address of a static object:
821 * Check if an address is part of freed initmem. After initmem is freed,
822 * memory can be allocated from it, and such allocations would then have
823 * addresses within the range [_stext, _end].
825 #ifndef arch_is_kernel_initmem_freed
826 static int arch_is_kernel_initmem_freed(unsigned long addr)
828 if (system_state < SYSTEM_FREEING_INITMEM)
831 return init_section_contains((void *)addr, 1);
835 static int static_obj(const void *obj)
837 unsigned long start = (unsigned long) &_stext,
838 end = (unsigned long) &_end,
839 addr = (unsigned long) obj;
841 if (arch_is_kernel_initmem_freed(addr))
847 if ((addr >= start) && (addr < end))
851 * in-kernel percpu var?
853 if (is_kernel_percpu_address(addr))
857 * module static or percpu var?
859 return is_module_address(addr) || is_module_percpu_address(addr);
864 * To make lock name printouts unique, we calculate a unique
865 * class->name_version generation counter. The caller must hold the graph
868 static int count_matching_names(struct lock_class *new_class)
870 struct lock_class *class;
873 if (!new_class->name)
876 list_for_each_entry(class, &all_lock_classes, lock_entry) {
877 if (new_class->key - new_class->subclass == class->key)
878 return class->name_version;
879 if (class->name && !strcmp(class->name, new_class->name))
880 count = max(count, class->name_version);
886 /* used from NMI context -- must be lockless */
887 static noinstr struct lock_class *
888 look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
890 struct lockdep_subclass_key *key;
891 struct hlist_head *hash_head;
892 struct lock_class *class;
894 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
895 instrumentation_begin();
898 "BUG: looking up invalid subclass: %u\n", subclass);
900 "turning off the locking correctness validator.\n");
902 instrumentation_end();
907 * If it is not initialised then it has never been locked,
908 * so it won't be present in the hash table.
910 if (unlikely(!lock->key))
914 * NOTE: the class-key must be unique. For dynamic locks, a static
915 * lock_class_key variable is passed in through the mutex_init()
916 * (or spin_lock_init()) call - which acts as the key. For static
917 * locks we use the lock object itself as the key.
919 BUILD_BUG_ON(sizeof(struct lock_class_key) >
920 sizeof(struct lockdep_map));
922 key = lock->key->subkeys + subclass;
924 hash_head = classhashentry(key);
927 * We do an RCU walk of the hash, see lockdep_free_key_range().
929 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
932 hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) {
933 if (class->key == key) {
935 * Huh! same key, different name? Did someone trample
936 * on some memory? We're most confused.
938 WARN_ONCE(class->name != lock->name &&
939 lock->key != &__lockdep_no_validate__,
940 "Looking for class \"%s\" with key %ps, but found a different class \"%s\" with the same key\n",
941 lock->name, lock->key, class->name);
950 * Static locks do not have their class-keys yet - for them the key is
951 * the lock object itself. If the lock is in the per cpu area, the
952 * canonical address of the lock (per cpu offset removed) is used.
954 static bool assign_lock_key(struct lockdep_map *lock)
956 unsigned long can_addr, addr = (unsigned long)lock;
960 * lockdep_free_key_range() assumes that struct lock_class_key
961 * objects do not overlap. Since we use the address of lock
962 * objects as class key for static objects, check whether the
963 * size of lock_class_key objects does not exceed the size of
964 * the smallest lock object.
966 BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
969 if (__is_kernel_percpu_address(addr, &can_addr))
970 lock->key = (void *)can_addr;
971 else if (__is_module_percpu_address(addr, &can_addr))
972 lock->key = (void *)can_addr;
973 else if (static_obj(lock))
974 lock->key = (void *)lock;
976 /* Debug-check: all keys must be persistent! */
978 pr_err("INFO: trying to register non-static key.\n");
979 pr_err("The code is fine but needs lockdep annotation, or maybe\n");
980 pr_err("you didn't initialize this object before use?\n");
981 pr_err("turning off the locking correctness validator.\n");
989 #ifdef CONFIG_DEBUG_LOCKDEP
991 /* Check whether element @e occurs in list @h */
992 static bool in_list(struct list_head *e, struct list_head *h)
996 list_for_each(f, h) {
1005 * Check whether entry @e occurs in any of the locks_after or locks_before
1008 static bool in_any_class_list(struct list_head *e)
1010 struct lock_class *class;
1013 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1014 class = &lock_classes[i];
1015 if (in_list(e, &class->locks_after) ||
1016 in_list(e, &class->locks_before))
1022 static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
1024 struct lock_list *e;
1026 list_for_each_entry(e, h, entry) {
1027 if (e->links_to != c) {
1028 printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
1030 (unsigned long)(e - list_entries),
1031 e->links_to && e->links_to->name ?
1032 e->links_to->name : "(?)",
1033 e->class && e->class->name ? e->class->name :
1041 #ifdef CONFIG_PROVE_LOCKING
1042 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1045 static bool check_lock_chain_key(struct lock_chain *chain)
1047 #ifdef CONFIG_PROVE_LOCKING
1048 u64 chain_key = INITIAL_CHAIN_KEY;
1051 for (i = chain->base; i < chain->base + chain->depth; i++)
1052 chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
1054 * The 'unsigned long long' casts avoid that a compiler warning
1055 * is reported when building tools/lib/lockdep.
1057 if (chain->chain_key != chain_key) {
1058 printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
1059 (unsigned long long)(chain - lock_chains),
1060 (unsigned long long)chain->chain_key,
1061 (unsigned long long)chain_key);
1068 static bool in_any_zapped_class_list(struct lock_class *class)
1070 struct pending_free *pf;
1073 for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
1074 if (in_list(&class->lock_entry, &pf->zapped))
1081 static bool __check_data_structures(void)
1083 struct lock_class *class;
1084 struct lock_chain *chain;
1085 struct hlist_head *head;
1086 struct lock_list *e;
1089 /* Check whether all classes occur in a lock list. */
1090 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1091 class = &lock_classes[i];
1092 if (!in_list(&class->lock_entry, &all_lock_classes) &&
1093 !in_list(&class->lock_entry, &free_lock_classes) &&
1094 !in_any_zapped_class_list(class)) {
1095 printk(KERN_INFO "class %px/%s is not in any class list\n",
1096 class, class->name ? : "(?)");
1101 /* Check whether all classes have valid lock lists. */
1102 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1103 class = &lock_classes[i];
1104 if (!class_lock_list_valid(class, &class->locks_before))
1106 if (!class_lock_list_valid(class, &class->locks_after))
1110 /* Check the chain_key of all lock chains. */
1111 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
1112 head = chainhash_table + i;
1113 hlist_for_each_entry_rcu(chain, head, entry) {
1114 if (!check_lock_chain_key(chain))
1120 * Check whether all list entries that are in use occur in a class
1123 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1124 e = list_entries + i;
1125 if (!in_any_class_list(&e->entry)) {
1126 printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
1127 (unsigned int)(e - list_entries),
1128 e->class->name ? : "(?)",
1129 e->links_to->name ? : "(?)");
1135 * Check whether all list entries that are not in use do not occur in
1136 * a class lock list.
1138 for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1139 e = list_entries + i;
1140 if (in_any_class_list(&e->entry)) {
1141 printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
1142 (unsigned int)(e - list_entries),
1143 e->class && e->class->name ? e->class->name :
1145 e->links_to && e->links_to->name ?
1146 e->links_to->name : "(?)");
1154 int check_consistency = 0;
1155 module_param(check_consistency, int, 0644);
1157 static void check_data_structures(void)
1159 static bool once = false;
1161 if (check_consistency && !once) {
1162 if (!__check_data_structures()) {
1169 #else /* CONFIG_DEBUG_LOCKDEP */
1171 static inline void check_data_structures(void) { }
1173 #endif /* CONFIG_DEBUG_LOCKDEP */
1175 static void init_chain_block_buckets(void);
1178 * Initialize the lock_classes[] array elements, the free_lock_classes list
1179 * and also the delayed_free structure.
1181 static void init_data_structures_once(void)
1183 static bool __read_mostly ds_initialized, rcu_head_initialized;
1186 if (likely(rcu_head_initialized))
1189 if (system_state >= SYSTEM_SCHEDULING) {
1190 init_rcu_head(&delayed_free.rcu_head);
1191 rcu_head_initialized = true;
1197 ds_initialized = true;
1199 INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
1200 INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
1202 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1203 list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
1204 INIT_LIST_HEAD(&lock_classes[i].locks_after);
1205 INIT_LIST_HEAD(&lock_classes[i].locks_before);
1207 init_chain_block_buckets();
1210 static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
1212 unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
1214 return lock_keys_hash + hash;
1217 /* Register a dynamically allocated key. */
1218 void lockdep_register_key(struct lock_class_key *key)
1220 struct hlist_head *hash_head;
1221 struct lock_class_key *k;
1222 unsigned long flags;
1224 if (WARN_ON_ONCE(static_obj(key)))
1226 hash_head = keyhashentry(key);
1228 raw_local_irq_save(flags);
1231 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1232 if (WARN_ON_ONCE(k == key))
1235 hlist_add_head_rcu(&key->hash_entry, hash_head);
1239 raw_local_irq_restore(flags);
1241 EXPORT_SYMBOL_GPL(lockdep_register_key);
1243 /* Check whether a key has been registered as a dynamic key. */
1244 static bool is_dynamic_key(const struct lock_class_key *key)
1246 struct hlist_head *hash_head;
1247 struct lock_class_key *k;
1250 if (WARN_ON_ONCE(static_obj(key)))
1254 * If lock debugging is disabled lock_keys_hash[] may contain
1255 * pointers to memory that has already been freed. Avoid triggering
1256 * a use-after-free in that case by returning early.
1261 hash_head = keyhashentry(key);
1264 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1276 * Register a lock's class in the hash-table, if the class is not present
1277 * yet. Otherwise we look it up. We cache the result in the lock object
1278 * itself, so actual lookup of the hash should be once per lock object.
1280 static struct lock_class *
1281 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
1283 struct lockdep_subclass_key *key;
1284 struct hlist_head *hash_head;
1285 struct lock_class *class;
1288 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1290 class = look_up_lock_class(lock, subclass);
1292 goto out_set_class_cache;
1295 if (!assign_lock_key(lock))
1297 } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
1301 key = lock->key->subkeys + subclass;
1302 hash_head = classhashentry(key);
1304 if (!graph_lock()) {
1308 * We have to do the hash-walk again, to avoid races
1311 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
1312 if (class->key == key)
1313 goto out_unlock_set;
1316 init_data_structures_once();
1318 /* Allocate a new lock class and add it to the hash. */
1319 class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
1322 if (!debug_locks_off_graph_unlock()) {
1326 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
1331 __set_bit(class - lock_classes, lock_classes_in_use);
1332 debug_atomic_inc(nr_unused_locks);
1334 class->name = lock->name;
1335 class->subclass = subclass;
1336 WARN_ON_ONCE(!list_empty(&class->locks_before));
1337 WARN_ON_ONCE(!list_empty(&class->locks_after));
1338 class->name_version = count_matching_names(class);
1339 class->wait_type_inner = lock->wait_type_inner;
1340 class->wait_type_outer = lock->wait_type_outer;
1341 class->lock_type = lock->lock_type;
1343 * We use RCU's safe list-add method to make
1344 * parallel walking of the hash-list safe:
1346 hlist_add_head_rcu(&class->hash_entry, hash_head);
1348 * Remove the class from the free list and add it to the global list
1351 list_move_tail(&class->lock_entry, &all_lock_classes);
1352 idx = class - lock_classes;
1353 if (idx > max_lock_class_idx)
1354 max_lock_class_idx = idx;
1356 if (verbose(class)) {
1359 printk("\nnew class %px: %s", class->key, class->name);
1360 if (class->name_version > 1)
1361 printk(KERN_CONT "#%d", class->name_version);
1362 printk(KERN_CONT "\n");
1365 if (!graph_lock()) {
1372 out_set_class_cache:
1373 if (!subclass || force)
1374 lock->class_cache[0] = class;
1375 else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
1376 lock->class_cache[subclass] = class;
1379 * Hash collision, did we smoke some? We found a class with a matching
1380 * hash but the subclass -- which is hashed in -- didn't match.
1382 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
1388 #ifdef CONFIG_PROVE_LOCKING
1390 * Allocate a lockdep entry. (assumes the graph_lock held, returns
1391 * with NULL on failure)
1393 static struct lock_list *alloc_list_entry(void)
1395 int idx = find_first_zero_bit(list_entries_in_use,
1396 ARRAY_SIZE(list_entries));
1398 if (idx >= ARRAY_SIZE(list_entries)) {
1399 if (!debug_locks_off_graph_unlock())
1402 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
1407 __set_bit(idx, list_entries_in_use);
1408 return list_entries + idx;
1412 * Add a new dependency to the head of the list:
1414 static int add_lock_to_list(struct lock_class *this,
1415 struct lock_class *links_to, struct list_head *head,
1416 u16 distance, u8 dep,
1417 const struct lock_trace *trace)
1419 struct lock_list *entry;
1421 * Lock not present yet - get a new dependency struct and
1422 * add it to the list:
1424 entry = alloc_list_entry();
1428 entry->class = this;
1429 entry->links_to = links_to;
1431 entry->distance = distance;
1432 entry->trace = trace;
1434 * Both allocation and removal are done under the graph lock; but
1435 * iteration is under RCU-sched; see look_up_lock_class() and
1436 * lockdep_free_key_range().
1438 list_add_tail_rcu(&entry->entry, head);
1444 * For good efficiency of modular, we use power of 2
1446 #define MAX_CIRCULAR_QUEUE_SIZE (1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS)
1447 #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
1450 * The circular_queue and helpers are used to implement graph
1451 * breadth-first search (BFS) algorithm, by which we can determine
1452 * whether there is a path from a lock to another. In deadlock checks,
1453 * a path from the next lock to be acquired to a previous held lock
1454 * indicates that adding the <prev> -> <next> lock dependency will
1455 * produce a circle in the graph. Breadth-first search instead of
1456 * depth-first search is used in order to find the shortest (circular)
1459 struct circular_queue {
1460 struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
1461 unsigned int front, rear;
1464 static struct circular_queue lock_cq;
1466 unsigned int max_bfs_queue_depth;
1468 static unsigned int lockdep_dependency_gen_id;
1470 static inline void __cq_init(struct circular_queue *cq)
1472 cq->front = cq->rear = 0;
1473 lockdep_dependency_gen_id++;
1476 static inline int __cq_empty(struct circular_queue *cq)
1478 return (cq->front == cq->rear);
1481 static inline int __cq_full(struct circular_queue *cq)
1483 return ((cq->rear + 1) & CQ_MASK) == cq->front;
1486 static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
1491 cq->element[cq->rear] = elem;
1492 cq->rear = (cq->rear + 1) & CQ_MASK;
1497 * Dequeue an element from the circular_queue, return a lock_list if
1498 * the queue is not empty, or NULL if otherwise.
1500 static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
1502 struct lock_list * lock;
1507 lock = cq->element[cq->front];
1508 cq->front = (cq->front + 1) & CQ_MASK;
1513 static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
1515 return (cq->rear - cq->front) & CQ_MASK;
1518 static inline void mark_lock_accessed(struct lock_list *lock)
1520 lock->class->dep_gen_id = lockdep_dependency_gen_id;
1523 static inline void visit_lock_entry(struct lock_list *lock,
1524 struct lock_list *parent)
1526 lock->parent = parent;
1529 static inline unsigned long lock_accessed(struct lock_list *lock)
1531 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
1534 static inline struct lock_list *get_lock_parent(struct lock_list *child)
1536 return child->parent;
1539 static inline int get_lock_depth(struct lock_list *child)
1542 struct lock_list *parent;
1544 while ((parent = get_lock_parent(child))) {
1552 * Return the forward or backward dependency list.
1554 * @lock: the lock_list to get its class's dependency list
1555 * @offset: the offset to struct lock_class to determine whether it is
1556 * locks_after or locks_before
1558 static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
1560 void *lock_class = lock->class;
1562 return lock_class + offset;
1565 * Return values of a bfs search:
1567 * BFS_E* indicates an error
1568 * BFS_R* indicates a result (match or not)
1570 * BFS_EINVALIDNODE: Find a invalid node in the graph.
1572 * BFS_EQUEUEFULL: The queue is full while doing the bfs.
1574 * BFS_RMATCH: Find the matched node in the graph, and put that node into
1577 * BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry
1581 BFS_EINVALIDNODE = -2,
1582 BFS_EQUEUEFULL = -1,
1588 * bfs_result < 0 means error
1590 static inline bool bfs_error(enum bfs_result res)
1596 * DEP_*_BIT in lock_list::dep
1598 * For dependency @prev -> @next:
1600 * SR: @prev is shared reader (->read != 0) and @next is recursive reader
1602 * ER: @prev is exclusive locker (->read == 0) and @next is recursive reader
1603 * SN: @prev is shared reader and @next is non-recursive locker (->read != 2)
1604 * EN: @prev is exclusive locker and @next is non-recursive locker
1606 * Note that we define the value of DEP_*_BITs so that:
1607 * bit0 is prev->read == 0
1608 * bit1 is next->read != 2
1610 #define DEP_SR_BIT (0 + (0 << 1)) /* 0 */
1611 #define DEP_ER_BIT (1 + (0 << 1)) /* 1 */
1612 #define DEP_SN_BIT (0 + (1 << 1)) /* 2 */
1613 #define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
1615 #define DEP_SR_MASK (1U << (DEP_SR_BIT))
1616 #define DEP_ER_MASK (1U << (DEP_ER_BIT))
1617 #define DEP_SN_MASK (1U << (DEP_SN_BIT))
1618 #define DEP_EN_MASK (1U << (DEP_EN_BIT))
1620 static inline unsigned int
1621 __calc_dep_bit(struct held_lock *prev, struct held_lock *next)
1623 return (prev->read == 0) + ((next->read != 2) << 1);
1626 static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
1628 return 1U << __calc_dep_bit(prev, next);
1632 * calculate the dep_bit for backwards edges. We care about whether @prev is
1633 * shared and whether @next is recursive.
1635 static inline unsigned int
1636 __calc_dep_bitb(struct held_lock *prev, struct held_lock *next)
1638 return (next->read != 2) + ((prev->read == 0) << 1);
1641 static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next)
1643 return 1U << __calc_dep_bitb(prev, next);
1647 * Initialize a lock_list entry @lock belonging to @class as the root for a BFS
1650 static inline void __bfs_init_root(struct lock_list *lock,
1651 struct lock_class *class)
1653 lock->class = class;
1654 lock->parent = NULL;
1659 * Initialize a lock_list entry @lock based on a lock acquisition @hlock as the
1660 * root for a BFS search.
1662 * ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure
1663 * that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)->
1666 static inline void bfs_init_root(struct lock_list *lock,
1667 struct held_lock *hlock)
1669 __bfs_init_root(lock, hlock_class(hlock));
1670 lock->only_xr = (hlock->read == 2);
1674 * Similar to bfs_init_root() but initialize the root for backwards BFS.
1676 * ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure
1677 * that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not
1678 * -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->).
1680 static inline void bfs_init_rootb(struct lock_list *lock,
1681 struct held_lock *hlock)
1683 __bfs_init_root(lock, hlock_class(hlock));
1684 lock->only_xr = (hlock->read != 0);
1687 static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset)
1689 if (!lock || !lock->parent)
1692 return list_next_or_null_rcu(get_dep_list(lock->parent, offset),
1693 &lock->entry, struct lock_list, entry);
1697 * Breadth-First Search to find a strong path in the dependency graph.
1699 * @source_entry: the source of the path we are searching for.
1700 * @data: data used for the second parameter of @match function
1701 * @match: match function for the search
1702 * @target_entry: pointer to the target of a matched path
1703 * @offset: the offset to struct lock_class to determine whether it is
1704 * locks_after or locks_before
1706 * We may have multiple edges (considering different kinds of dependencies,
1707 * e.g. ER and SN) between two nodes in the dependency graph. But
1708 * only the strong dependency path in the graph is relevant to deadlocks. A
1709 * strong dependency path is a dependency path that doesn't have two adjacent
1710 * dependencies as -(*R)-> -(S*)->, please see:
1712 * Documentation/locking/lockdep-design.rst
1714 * for more explanation of the definition of strong dependency paths
1716 * In __bfs(), we only traverse in the strong dependency path:
1718 * In lock_list::only_xr, we record whether the previous dependency only
1719 * has -(*R)-> in the search, and if it does (prev only has -(*R)->), we
1720 * filter out any -(S*)-> in the current dependency and after that, the
1721 * ->only_xr is set according to whether we only have -(*R)-> left.
1723 static enum bfs_result __bfs(struct lock_list *source_entry,
1725 bool (*match)(struct lock_list *entry, void *data),
1726 bool (*skip)(struct lock_list *entry, void *data),
1727 struct lock_list **target_entry,
1730 struct circular_queue *cq = &lock_cq;
1731 struct lock_list *lock = NULL;
1732 struct lock_list *entry;
1733 struct list_head *head;
1734 unsigned int cq_depth;
1737 lockdep_assert_locked();
1740 __cq_enqueue(cq, source_entry);
1742 while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) {
1744 return BFS_EINVALIDNODE;
1747 * Step 1: check whether we already finish on this one.
1749 * If we have visited all the dependencies from this @lock to
1750 * others (iow, if we have visited all lock_list entries in
1751 * @lock->class->locks_{after,before}) we skip, otherwise go
1752 * and visit all the dependencies in the list and mark this
1755 if (lock_accessed(lock))
1758 mark_lock_accessed(lock);
1761 * Step 2: check whether prev dependency and this form a strong
1764 if (lock->parent) { /* Parent exists, check prev dependency */
1766 bool prev_only_xr = lock->parent->only_xr;
1769 * Mask out all -(S*)-> if we only have *R in previous
1770 * step, because -(*R)-> -(S*)-> don't make up a strong
1774 dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
1776 /* If nothing left, we skip */
1780 /* If there are only -(*R)-> left, set that for the next step */
1781 lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK));
1785 * Step 3: we haven't visited this and there is a strong
1786 * dependency path to this, so check with @match.
1787 * If @skip is provide and returns true, we skip this
1788 * lock (and any path this lock is in).
1790 if (skip && skip(lock, data))
1793 if (match(lock, data)) {
1794 *target_entry = lock;
1799 * Step 4: if not match, expand the path by adding the
1800 * forward or backwards dependencies in the search
1804 head = get_dep_list(lock, offset);
1805 list_for_each_entry_rcu(entry, head, entry) {
1806 visit_lock_entry(entry, lock);
1809 * Note we only enqueue the first of the list into the
1810 * queue, because we can always find a sibling
1811 * dependency from one (see __bfs_next()), as a result
1812 * the space of queue is saved.
1819 if (__cq_enqueue(cq, entry))
1820 return BFS_EQUEUEFULL;
1822 cq_depth = __cq_get_elem_count(cq);
1823 if (max_bfs_queue_depth < cq_depth)
1824 max_bfs_queue_depth = cq_depth;
1828 return BFS_RNOMATCH;
1831 static inline enum bfs_result
1832 __bfs_forwards(struct lock_list *src_entry,
1834 bool (*match)(struct lock_list *entry, void *data),
1835 bool (*skip)(struct lock_list *entry, void *data),
1836 struct lock_list **target_entry)
1838 return __bfs(src_entry, data, match, skip, target_entry,
1839 offsetof(struct lock_class, locks_after));
1843 static inline enum bfs_result
1844 __bfs_backwards(struct lock_list *src_entry,
1846 bool (*match)(struct lock_list *entry, void *data),
1847 bool (*skip)(struct lock_list *entry, void *data),
1848 struct lock_list **target_entry)
1850 return __bfs(src_entry, data, match, skip, target_entry,
1851 offsetof(struct lock_class, locks_before));
1855 static void print_lock_trace(const struct lock_trace *trace,
1856 unsigned int spaces)
1858 stack_trace_print(trace->entries, trace->nr_entries, spaces);
1862 * Print a dependency chain entry (this is only done when a deadlock
1863 * has been detected):
1865 static noinline void
1866 print_circular_bug_entry(struct lock_list *target, int depth)
1868 if (debug_locks_silent)
1870 printk("\n-> #%u", depth);
1871 print_lock_name(target->class);
1872 printk(KERN_CONT ":\n");
1873 print_lock_trace(target->trace, 6);
1877 print_circular_lock_scenario(struct held_lock *src,
1878 struct held_lock *tgt,
1879 struct lock_list *prt)
1881 struct lock_class *source = hlock_class(src);
1882 struct lock_class *target = hlock_class(tgt);
1883 struct lock_class *parent = prt->class;
1884 int src_read = src->read;
1885 int tgt_read = tgt->read;
1888 * A direct locking problem where unsafe_class lock is taken
1889 * directly by safe_class lock, then all we need to show
1890 * is the deadlock scenario, as it is obvious that the
1891 * unsafe lock is taken under the safe lock.
1893 * But if there is a chain instead, where the safe lock takes
1894 * an intermediate lock (middle_class) where this lock is
1895 * not the same as the safe lock, then the lock chain is
1896 * used to describe the problem. Otherwise we would need
1897 * to show a different CPU case for each link in the chain
1898 * from the safe_class lock to the unsafe_class lock.
1900 if (parent != source) {
1901 printk("Chain exists of:\n ");
1902 __print_lock_name(source);
1903 printk(KERN_CONT " --> ");
1904 __print_lock_name(parent);
1905 printk(KERN_CONT " --> ");
1906 __print_lock_name(target);
1907 printk(KERN_CONT "\n\n");
1910 printk(" Possible unsafe locking scenario:\n\n");
1911 printk(" CPU0 CPU1\n");
1912 printk(" ---- ----\n");
1917 __print_lock_name(target);
1918 printk(KERN_CONT ");\n");
1920 __print_lock_name(parent);
1921 printk(KERN_CONT ");\n");
1923 __print_lock_name(target);
1924 printk(KERN_CONT ");\n");
1931 __print_lock_name(source);
1932 printk(KERN_CONT ");\n");
1933 printk("\n *** DEADLOCK ***\n\n");
1937 * When a circular dependency is detected, print the
1940 static noinline void
1941 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1942 struct held_lock *check_src,
1943 struct held_lock *check_tgt)
1945 struct task_struct *curr = current;
1947 if (debug_locks_silent)
1951 pr_warn("======================================================\n");
1952 pr_warn("WARNING: possible circular locking dependency detected\n");
1953 print_kernel_ident();
1954 pr_warn("------------------------------------------------------\n");
1955 pr_warn("%s/%d is trying to acquire lock:\n",
1956 curr->comm, task_pid_nr(curr));
1957 print_lock(check_src);
1959 pr_warn("\nbut task is already holding lock:\n");
1961 print_lock(check_tgt);
1962 pr_warn("\nwhich lock already depends on the new lock.\n\n");
1963 pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
1965 print_circular_bug_entry(entry, depth);
1969 * We are about to add A -> B into the dependency graph, and in __bfs() a
1970 * strong dependency path A -> .. -> B is found: hlock_class equals
1973 * If A -> .. -> B can replace A -> B in any __bfs() search (means the former
1974 * is _stronger_ than or equal to the latter), we consider A -> B as redundant.
1975 * For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A
1976 * -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the
1977 * dependency graph, as any strong path ..-> A -> B ->.. we can get with
1978 * having dependency A -> B, we could already get a equivalent path ..-> A ->
1979 * .. -> B -> .. with A -> .. -> B. Therefore A -> B is redundant.
1981 * We need to make sure both the start and the end of A -> .. -> B is not
1982 * weaker than A -> B. For the start part, please see the comment in
1983 * check_redundant(). For the end part, we need:
1987 * a) A -> B is -(*R)-> (everything is not weaker than that)
1991 * b) A -> .. -> B is -(*N)-> (nothing is stronger than this)
1994 static inline bool hlock_equal(struct lock_list *entry, void *data)
1996 struct held_lock *hlock = (struct held_lock *)data;
1998 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
1999 (hlock->read == 2 || /* A -> B is -(*R)-> */
2000 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
2004 * We are about to add B -> A into the dependency graph, and in __bfs() a
2005 * strong dependency path A -> .. -> B is found: hlock_class equals
2008 * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong
2009 * dependency cycle, that means:
2013 * a) B -> A is -(E*)->
2017 * b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B)
2019 * as then we don't have -(*R)-> -(S*)-> in the cycle.
2021 static inline bool hlock_conflict(struct lock_list *entry, void *data)
2023 struct held_lock *hlock = (struct held_lock *)data;
2025 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
2026 (hlock->read == 0 || /* B -> A is -(E*)-> */
2027 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
2030 static noinline void print_circular_bug(struct lock_list *this,
2031 struct lock_list *target,
2032 struct held_lock *check_src,
2033 struct held_lock *check_tgt)
2035 struct task_struct *curr = current;
2036 struct lock_list *parent;
2037 struct lock_list *first_parent;
2040 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2043 this->trace = save_trace();
2047 depth = get_lock_depth(target);
2049 print_circular_bug_header(target, depth, check_src, check_tgt);
2051 parent = get_lock_parent(target);
2052 first_parent = parent;
2055 print_circular_bug_entry(parent, --depth);
2056 parent = get_lock_parent(parent);
2059 printk("\nother info that might help us debug this:\n\n");
2060 print_circular_lock_scenario(check_src, check_tgt,
2063 lockdep_print_held_locks(curr);
2065 printk("\nstack backtrace:\n");
2069 static noinline void print_bfs_bug(int ret)
2071 if (!debug_locks_off_graph_unlock())
2075 * Breadth-first-search failed, graph got corrupted?
2077 WARN(1, "lockdep bfs error:%d\n", ret);
2080 static bool noop_count(struct lock_list *entry, void *data)
2082 (*(unsigned long *)data)++;
2086 static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
2088 unsigned long count = 0;
2089 struct lock_list *target_entry;
2091 __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
2095 unsigned long lockdep_count_forward_deps(struct lock_class *class)
2097 unsigned long ret, flags;
2098 struct lock_list this;
2100 __bfs_init_root(&this, class);
2102 raw_local_irq_save(flags);
2104 ret = __lockdep_count_forward_deps(&this);
2106 raw_local_irq_restore(flags);
2111 static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
2113 unsigned long count = 0;
2114 struct lock_list *target_entry;
2116 __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
2121 unsigned long lockdep_count_backward_deps(struct lock_class *class)
2123 unsigned long ret, flags;
2124 struct lock_list this;
2126 __bfs_init_root(&this, class);
2128 raw_local_irq_save(flags);
2130 ret = __lockdep_count_backward_deps(&this);
2132 raw_local_irq_restore(flags);
2138 * Check that the dependency graph starting at <src> can lead to
2141 static noinline enum bfs_result
2142 check_path(struct held_lock *target, struct lock_list *src_entry,
2143 bool (*match)(struct lock_list *entry, void *data),
2144 bool (*skip)(struct lock_list *entry, void *data),
2145 struct lock_list **target_entry)
2147 enum bfs_result ret;
2149 ret = __bfs_forwards(src_entry, target, match, skip, target_entry);
2151 if (unlikely(bfs_error(ret)))
2158 * Prove that the dependency graph starting at <src> can not
2159 * lead to <target>. If it can, there is a circle when adding
2160 * <target> -> <src> dependency.
2162 * Print an error and return BFS_RMATCH if it does.
2164 static noinline enum bfs_result
2165 check_noncircular(struct held_lock *src, struct held_lock *target,
2166 struct lock_trace **const trace)
2168 enum bfs_result ret;
2169 struct lock_list *target_entry;
2170 struct lock_list src_entry;
2172 bfs_init_root(&src_entry, src);
2174 debug_atomic_inc(nr_cyclic_checks);
2176 ret = check_path(target, &src_entry, hlock_conflict, NULL, &target_entry);
2178 if (unlikely(ret == BFS_RMATCH)) {
2181 * If save_trace fails here, the printing might
2182 * trigger a WARN but because of the !nr_entries it
2183 * should not do bad things.
2185 *trace = save_trace();
2188 print_circular_bug(&src_entry, target_entry, src, target);
2194 #ifdef CONFIG_TRACE_IRQFLAGS
2197 * Forwards and backwards subgraph searching, for the purposes of
2198 * proving that two subgraphs can be connected by a new dependency
2199 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
2201 * A irq safe->unsafe deadlock happens with the following conditions:
2203 * 1) We have a strong dependency path A -> ... -> B
2205 * 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore
2206 * irq can create a new dependency B -> A (consider the case that a holder
2207 * of B gets interrupted by an irq whose handler will try to acquire A).
2209 * 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a
2212 * For the usage bits of B:
2213 * a) if A -> B is -(*N)->, then B -> A could be any type, so any
2214 * ENABLED_IRQ usage suffices.
2215 * b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only
2216 * ENABLED_IRQ_*_READ usage suffices.
2218 * For the usage bits of A:
2219 * c) if A -> B is -(E*)->, then B -> A could be any type, so any
2220 * USED_IN_IRQ usage suffices.
2221 * d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only
2222 * USED_IN_IRQ_*_READ usage suffices.
2226 * There is a strong dependency path in the dependency graph: A -> B, and now
2227 * we need to decide which usage bit of A should be accumulated to detect
2228 * safe->unsafe bugs.
2230 * Note that usage_accumulate() is used in backwards search, so ->only_xr
2231 * stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true).
2233 * As above, if only_xr is false, which means A -> B has -(E*)-> dependency
2234 * path, any usage of A should be considered. Otherwise, we should only
2235 * consider _READ usage.
2237 static inline bool usage_accumulate(struct lock_list *entry, void *mask)
2239 if (!entry->only_xr)
2240 *(unsigned long *)mask |= entry->class->usage_mask;
2241 else /* Mask out _READ usage bits */
2242 *(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ);
2248 * There is a strong dependency path in the dependency graph: A -> B, and now
2249 * we need to decide which usage bit of B conflicts with the usage bits of A,
2250 * i.e. which usage bit of B may introduce safe->unsafe deadlocks.
2252 * As above, if only_xr is false, which means A -> B has -(*N)-> dependency
2253 * path, any usage of B should be considered. Otherwise, we should only
2254 * consider _READ usage.
2256 static inline bool usage_match(struct lock_list *entry, void *mask)
2258 if (!entry->only_xr)
2259 return !!(entry->class->usage_mask & *(unsigned long *)mask);
2260 else /* Mask out _READ usage bits */
2261 return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask);
2264 static inline bool usage_skip(struct lock_list *entry, void *mask)
2266 if (entry->class->lock_type == LD_LOCK_NORMAL)
2270 * Skip local_lock() for irq inversion detection.
2272 * For !RT, local_lock() is not a real lock, so it won't carry any
2275 * For RT, an irq inversion happens when we have lock A and B, and on
2276 * some CPU we can have:
2282 * where lock(B) cannot sleep, and we have a dependency B -> ... -> A.
2284 * Now we prove local_lock() cannot exist in that dependency. First we
2285 * have the observation for any lock chain L1 -> ... -> Ln, for any
2286 * 1 <= i <= n, Li.inner_wait_type <= L1.inner_wait_type, otherwise
2287 * wait context check will complain. And since B is not a sleep lock,
2288 * therefore B.inner_wait_type >= 2, and since the inner_wait_type of
2289 * local_lock() is 3, which is greater than 2, therefore there is no
2290 * way the local_lock() exists in the dependency B -> ... -> A.
2292 * As a result, we will skip local_lock(), when we search for irq
2295 if (entry->class->lock_type == LD_LOCK_PERCPU &&
2296 DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
2300 * Skip WAIT_OVERRIDE for irq inversion detection -- it's not actually
2301 * a lock and only used to override the wait_type.
2308 * Find a node in the forwards-direction dependency sub-graph starting
2309 * at @root->class that matches @bit.
2311 * Return BFS_MATCH if such a node exists in the subgraph, and put that node
2312 * into *@target_entry.
2314 static enum bfs_result
2315 find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
2316 struct lock_list **target_entry)
2318 enum bfs_result result;
2320 debug_atomic_inc(nr_find_usage_forwards_checks);
2322 result = __bfs_forwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2328 * Find a node in the backwards-direction dependency sub-graph starting
2329 * at @root->class that matches @bit.
2331 static enum bfs_result
2332 find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
2333 struct lock_list **target_entry)
2335 enum bfs_result result;
2337 debug_atomic_inc(nr_find_usage_backwards_checks);
2339 result = __bfs_backwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2344 static void print_lock_class_header(struct lock_class *class, int depth)
2348 printk("%*s->", depth, "");
2349 print_lock_name(class);
2350 #ifdef CONFIG_DEBUG_LOCKDEP
2351 printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
2353 printk(KERN_CONT " {\n");
2355 for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
2356 if (class->usage_mask & (1 << bit)) {
2359 len += printk("%*s %s", depth, "", usage_str[bit]);
2360 len += printk(KERN_CONT " at:\n");
2361 print_lock_trace(class->usage_traces[bit], len);
2364 printk("%*s }\n", depth, "");
2366 printk("%*s ... key at: [<%px>] %pS\n",
2367 depth, "", class->key, class->key);
2371 * Dependency path printing:
2373 * After BFS we get a lock dependency path (linked via ->parent of lock_list),
2374 * printing out each lock in the dependency path will help on understanding how
2375 * the deadlock could happen. Here are some details about dependency path
2378 * 1) A lock_list can be either forwards or backwards for a lock dependency,
2379 * for a lock dependency A -> B, there are two lock_lists:
2381 * a) lock_list in the ->locks_after list of A, whose ->class is B and
2382 * ->links_to is A. In this case, we can say the lock_list is
2383 * "A -> B" (forwards case).
2385 * b) lock_list in the ->locks_before list of B, whose ->class is A
2386 * and ->links_to is B. In this case, we can say the lock_list is
2387 * "B <- A" (bacwards case).
2389 * The ->trace of both a) and b) point to the call trace where B was
2390 * acquired with A held.
2392 * 2) A "helper" lock_list is introduced during BFS, this lock_list doesn't
2393 * represent a certain lock dependency, it only provides an initial entry
2394 * for BFS. For example, BFS may introduce a "helper" lock_list whose
2395 * ->class is A, as a result BFS will search all dependencies starting with
2396 * A, e.g. A -> B or A -> C.
2398 * The notation of a forwards helper lock_list is like "-> A", which means
2399 * we should search the forwards dependencies starting with "A", e.g A -> B
2402 * The notation of a bacwards helper lock_list is like "<- B", which means
2403 * we should search the backwards dependencies ending with "B", e.g.
2408 * printk the shortest lock dependencies from @root to @leaf in reverse order.
2410 * We have a lock dependency path as follow:
2416 * | lock_list | <--------- | lock_list | ... | lock_list | <--------- | lock_list |
2417 * | -> L1 | | L1 -> L2 | ... |Ln-2 -> Ln-1| | Ln-1 -> Ln|
2419 * , so it's natural that we start from @leaf and print every ->class and
2420 * ->trace until we reach the @root.
2423 print_shortest_lock_dependencies(struct lock_list *leaf,
2424 struct lock_list *root)
2426 struct lock_list *entry = leaf;
2429 /*compute depth from generated tree by BFS*/
2430 depth = get_lock_depth(leaf);
2433 print_lock_class_header(entry->class, depth);
2434 printk("%*s ... acquired at:\n", depth, "");
2435 print_lock_trace(entry->trace, 2);
2438 if (depth == 0 && (entry != root)) {
2439 printk("lockdep:%s bad path found in chain graph\n", __func__);
2443 entry = get_lock_parent(entry);
2445 } while (entry && (depth >= 0));
2449 * printk the shortest lock dependencies from @leaf to @root.
2451 * We have a lock dependency path (from a backwards search) as follow:
2457 * | lock_list | ---------> | lock_list | ... | lock_list | ---------> | lock_list |
2458 * | L2 <- L1 | | L3 <- L2 | ... | Ln <- Ln-1 | | <- Ln |
2460 * , so when we iterate from @leaf to @root, we actually print the lock
2461 * dependency path L1 -> L2 -> .. -> Ln in the non-reverse order.
2463 * Another thing to notice here is that ->class of L2 <- L1 is L1, while the
2464 * ->trace of L2 <- L1 is the call trace of L2, in fact we don't have the call
2465 * trace of L1 in the dependency path, which is alright, because most of the
2466 * time we can figure out where L1 is held from the call trace of L2.
2469 print_shortest_lock_dependencies_backwards(struct lock_list *leaf,
2470 struct lock_list *root)
2472 struct lock_list *entry = leaf;
2473 const struct lock_trace *trace = NULL;
2476 /*compute depth from generated tree by BFS*/
2477 depth = get_lock_depth(leaf);
2480 print_lock_class_header(entry->class, depth);
2482 printk("%*s ... acquired at:\n", depth, "");
2483 print_lock_trace(trace, 2);
2488 * Record the pointer to the trace for the next lock_list
2489 * entry, see the comments for the function.
2491 trace = entry->trace;
2493 if (depth == 0 && (entry != root)) {
2494 printk("lockdep:%s bad path found in chain graph\n", __func__);
2498 entry = get_lock_parent(entry);
2500 } while (entry && (depth >= 0));
2504 print_irq_lock_scenario(struct lock_list *safe_entry,
2505 struct lock_list *unsafe_entry,
2506 struct lock_class *prev_class,
2507 struct lock_class *next_class)
2509 struct lock_class *safe_class = safe_entry->class;
2510 struct lock_class *unsafe_class = unsafe_entry->class;
2511 struct lock_class *middle_class = prev_class;
2513 if (middle_class == safe_class)
2514 middle_class = next_class;
2517 * A direct locking problem where unsafe_class lock is taken
2518 * directly by safe_class lock, then all we need to show
2519 * is the deadlock scenario, as it is obvious that the
2520 * unsafe lock is taken under the safe lock.
2522 * But if there is a chain instead, where the safe lock takes
2523 * an intermediate lock (middle_class) where this lock is
2524 * not the same as the safe lock, then the lock chain is
2525 * used to describe the problem. Otherwise we would need
2526 * to show a different CPU case for each link in the chain
2527 * from the safe_class lock to the unsafe_class lock.
2529 if (middle_class != unsafe_class) {
2530 printk("Chain exists of:\n ");
2531 __print_lock_name(safe_class);
2532 printk(KERN_CONT " --> ");
2533 __print_lock_name(middle_class);
2534 printk(KERN_CONT " --> ");
2535 __print_lock_name(unsafe_class);
2536 printk(KERN_CONT "\n\n");
2539 printk(" Possible interrupt unsafe locking scenario:\n\n");
2540 printk(" CPU0 CPU1\n");
2541 printk(" ---- ----\n");
2543 __print_lock_name(unsafe_class);
2544 printk(KERN_CONT ");\n");
2545 printk(" local_irq_disable();\n");
2547 __print_lock_name(safe_class);
2548 printk(KERN_CONT ");\n");
2550 __print_lock_name(middle_class);
2551 printk(KERN_CONT ");\n");
2552 printk(" <Interrupt>\n");
2554 __print_lock_name(safe_class);
2555 printk(KERN_CONT ");\n");
2556 printk("\n *** DEADLOCK ***\n\n");
2560 print_bad_irq_dependency(struct task_struct *curr,
2561 struct lock_list *prev_root,
2562 struct lock_list *next_root,
2563 struct lock_list *backwards_entry,
2564 struct lock_list *forwards_entry,
2565 struct held_lock *prev,
2566 struct held_lock *next,
2567 enum lock_usage_bit bit1,
2568 enum lock_usage_bit bit2,
2569 const char *irqclass)
2571 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2575 pr_warn("=====================================================\n");
2576 pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
2577 irqclass, irqclass);
2578 print_kernel_ident();
2579 pr_warn("-----------------------------------------------------\n");
2580 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
2581 curr->comm, task_pid_nr(curr),
2582 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
2583 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
2584 lockdep_hardirqs_enabled(),
2585 curr->softirqs_enabled);
2588 pr_warn("\nand this task is already holding:\n");
2590 pr_warn("which would create a new lock dependency:\n");
2591 print_lock_name(hlock_class(prev));
2593 print_lock_name(hlock_class(next));
2596 pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
2598 print_lock_name(backwards_entry->class);
2599 pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
2601 print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
2603 pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
2604 print_lock_name(forwards_entry->class);
2605 pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
2608 print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
2610 pr_warn("\nother info that might help us debug this:\n\n");
2611 print_irq_lock_scenario(backwards_entry, forwards_entry,
2612 hlock_class(prev), hlock_class(next));
2614 lockdep_print_held_locks(curr);
2616 pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
2617 print_shortest_lock_dependencies_backwards(backwards_entry, prev_root);
2619 pr_warn("\nthe dependencies between the lock to be acquired");
2620 pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
2621 next_root->trace = save_trace();
2622 if (!next_root->trace)
2624 print_shortest_lock_dependencies(forwards_entry, next_root);
2626 pr_warn("\nstack backtrace:\n");
2630 static const char *state_names[] = {
2631 #define LOCKDEP_STATE(__STATE) \
2632 __stringify(__STATE),
2633 #include "lockdep_states.h"
2634 #undef LOCKDEP_STATE
2637 static const char *state_rnames[] = {
2638 #define LOCKDEP_STATE(__STATE) \
2639 __stringify(__STATE)"-READ",
2640 #include "lockdep_states.h"
2641 #undef LOCKDEP_STATE
2644 static inline const char *state_name(enum lock_usage_bit bit)
2646 if (bit & LOCK_USAGE_READ_MASK)
2647 return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
2649 return state_names[bit >> LOCK_USAGE_DIR_MASK];
2653 * The bit number is encoded like:
2655 * bit0: 0 exclusive, 1 read lock
2656 * bit1: 0 used in irq, 1 irq enabled
2659 static int exclusive_bit(int new_bit)
2661 int state = new_bit & LOCK_USAGE_STATE_MASK;
2662 int dir = new_bit & LOCK_USAGE_DIR_MASK;
2665 * keep state, bit flip the direction and strip read.
2667 return state | (dir ^ LOCK_USAGE_DIR_MASK);
2671 * Observe that when given a bitmask where each bitnr is encoded as above, a
2672 * right shift of the mask transforms the individual bitnrs as -1 and
2673 * conversely, a left shift transforms into +1 for the individual bitnrs.
2675 * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
2676 * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
2677 * instead by subtracting the bit number by 2, or shifting the mask right by 2.
2679 * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
2681 * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
2682 * all bits set) and recompose with bitnr1 flipped.
2684 static unsigned long invert_dir_mask(unsigned long mask)
2686 unsigned long excl = 0;
2689 excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
2690 excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
2696 * Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ
2697 * usage may cause deadlock too, for example:
2701 * write_lock(l1); <irq enabled>
2707 * , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2
2708 * will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible
2711 * In fact, all of the following cases may cause deadlocks:
2713 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*
2714 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*
2715 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ
2716 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ
2718 * As a result, to calculate the "exclusive mask", first we invert the
2719 * direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with
2720 * bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all
2721 * bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*).
2723 static unsigned long exclusive_mask(unsigned long mask)
2725 unsigned long excl = invert_dir_mask(mask);
2727 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2728 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2734 * Retrieve the _possible_ original mask to which @mask is
2735 * exclusive. Ie: this is the opposite of exclusive_mask().
2736 * Note that 2 possible original bits can match an exclusive
2737 * bit: one has LOCK_USAGE_READ_MASK set, the other has it
2738 * cleared. So both are returned for each exclusive bit.
2740 static unsigned long original_mask(unsigned long mask)
2742 unsigned long excl = invert_dir_mask(mask);
2744 /* Include read in existing usages */
2745 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2746 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2752 * Find the first pair of bit match between an original
2753 * usage mask and an exclusive usage mask.
2755 static int find_exclusive_match(unsigned long mask,
2756 unsigned long excl_mask,
2757 enum lock_usage_bit *bitp,
2758 enum lock_usage_bit *excl_bitp)
2760 int bit, excl, excl_read;
2762 for_each_set_bit(bit, &mask, LOCK_USED) {
2764 * exclusive_bit() strips the read bit, however,
2765 * LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need
2766 * to search excl | LOCK_USAGE_READ_MASK as well.
2768 excl = exclusive_bit(bit);
2769 excl_read = excl | LOCK_USAGE_READ_MASK;
2770 if (excl_mask & lock_flag(excl)) {
2774 } else if (excl_mask & lock_flag(excl_read)) {
2776 *excl_bitp = excl_read;
2784 * Prove that the new dependency does not connect a hardirq-safe(-read)
2785 * lock with a hardirq-unsafe lock - to achieve this we search
2786 * the backwards-subgraph starting at <prev>, and the
2787 * forwards-subgraph starting at <next>:
2789 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
2790 struct held_lock *next)
2792 unsigned long usage_mask = 0, forward_mask, backward_mask;
2793 enum lock_usage_bit forward_bit = 0, backward_bit = 0;
2794 struct lock_list *target_entry1;
2795 struct lock_list *target_entry;
2796 struct lock_list this, that;
2797 enum bfs_result ret;
2800 * Step 1: gather all hard/soft IRQs usages backward in an
2801 * accumulated usage mask.
2803 bfs_init_rootb(&this, prev);
2805 ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, usage_skip, NULL);
2806 if (bfs_error(ret)) {
2811 usage_mask &= LOCKF_USED_IN_IRQ_ALL;
2816 * Step 2: find exclusive uses forward that match the previous
2817 * backward accumulated mask.
2819 forward_mask = exclusive_mask(usage_mask);
2821 bfs_init_root(&that, next);
2823 ret = find_usage_forwards(&that, forward_mask, &target_entry1);
2824 if (bfs_error(ret)) {
2828 if (ret == BFS_RNOMATCH)
2832 * Step 3: we found a bad match! Now retrieve a lock from the backward
2833 * list whose usage mask matches the exclusive usage mask from the
2834 * lock found on the forward list.
2836 * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering
2839 * When trying to add A -> B to the graph, we find that there is a
2840 * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M,
2841 * that B -> ... -> M. However M is **softirq-safe**, if we use exact
2842 * invert bits of M's usage_mask, we will find another lock N that is
2843 * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not
2844 * cause a inversion deadlock.
2846 backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL);
2848 ret = find_usage_backwards(&this, backward_mask, &target_entry);
2849 if (bfs_error(ret)) {
2853 if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH))
2857 * Step 4: narrow down to a pair of incompatible usage bits
2860 ret = find_exclusive_match(target_entry->class->usage_mask,
2861 target_entry1->class->usage_mask,
2862 &backward_bit, &forward_bit);
2863 if (DEBUG_LOCKS_WARN_ON(ret == -1))
2866 print_bad_irq_dependency(curr, &this, &that,
2867 target_entry, target_entry1,
2869 backward_bit, forward_bit,
2870 state_name(backward_bit));
2877 static inline int check_irq_usage(struct task_struct *curr,
2878 struct held_lock *prev, struct held_lock *next)
2883 static inline bool usage_skip(struct lock_list *entry, void *mask)
2888 #endif /* CONFIG_TRACE_IRQFLAGS */
2890 #ifdef CONFIG_LOCKDEP_SMALL
2892 * Check that the dependency graph starting at <src> can lead to
2893 * <target> or not. If it can, <src> -> <target> dependency is already
2896 * Return BFS_RMATCH if it does, or BFS_RNOMATCH if it does not, return BFS_E* if
2897 * any error appears in the bfs search.
2899 static noinline enum bfs_result
2900 check_redundant(struct held_lock *src, struct held_lock *target)
2902 enum bfs_result ret;
2903 struct lock_list *target_entry;
2904 struct lock_list src_entry;
2906 bfs_init_root(&src_entry, src);
2908 * Special setup for check_redundant().
2910 * To report redundant, we need to find a strong dependency path that
2911 * is equal to or stronger than <src> -> <target>. So if <src> is E,
2912 * we need to let __bfs() only search for a path starting at a -(E*)->,
2913 * we achieve this by setting the initial node's ->only_xr to true in
2914 * that case. And if <prev> is S, we set initial ->only_xr to false
2915 * because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant.
2917 src_entry.only_xr = src->read == 0;
2919 debug_atomic_inc(nr_redundant_checks);
2922 * Note: we skip local_lock() for redundant check, because as the
2923 * comment in usage_skip(), A -> local_lock() -> B and A -> B are not
2926 ret = check_path(target, &src_entry, hlock_equal, usage_skip, &target_entry);
2928 if (ret == BFS_RMATCH)
2929 debug_atomic_inc(nr_redundant);
2936 static inline enum bfs_result
2937 check_redundant(struct held_lock *src, struct held_lock *target)
2939 return BFS_RNOMATCH;
2944 static void inc_chains(int irq_context)
2946 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2947 nr_hardirq_chains++;
2948 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2949 nr_softirq_chains++;
2951 nr_process_chains++;
2954 static void dec_chains(int irq_context)
2956 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2957 nr_hardirq_chains--;
2958 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2959 nr_softirq_chains--;
2961 nr_process_chains--;
2965 print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
2967 struct lock_class *next = hlock_class(nxt);
2968 struct lock_class *prev = hlock_class(prv);
2970 printk(" Possible unsafe locking scenario:\n\n");
2974 __print_lock_name(prev);
2975 printk(KERN_CONT ");\n");
2977 __print_lock_name(next);
2978 printk(KERN_CONT ");\n");
2979 printk("\n *** DEADLOCK ***\n\n");
2980 printk(" May be due to missing lock nesting notation\n\n");
2984 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
2985 struct held_lock *next)
2987 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2991 pr_warn("============================================\n");
2992 pr_warn("WARNING: possible recursive locking detected\n");
2993 print_kernel_ident();
2994 pr_warn("--------------------------------------------\n");
2995 pr_warn("%s/%d is trying to acquire lock:\n",
2996 curr->comm, task_pid_nr(curr));
2998 pr_warn("\nbut task is already holding lock:\n");
3001 pr_warn("\nother info that might help us debug this:\n");
3002 print_deadlock_scenario(next, prev);
3003 lockdep_print_held_locks(curr);
3005 pr_warn("\nstack backtrace:\n");
3010 * Check whether we are holding such a class already.
3012 * (Note that this has to be done separately, because the graph cannot
3013 * detect such classes of deadlocks.)
3015 * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same
3016 * lock class is held but nest_lock is also held, i.e. we rely on the
3017 * nest_lock to avoid the deadlock.
3020 check_deadlock(struct task_struct *curr, struct held_lock *next)
3022 struct held_lock *prev;
3023 struct held_lock *nest = NULL;
3026 for (i = 0; i < curr->lockdep_depth; i++) {
3027 prev = curr->held_locks + i;
3029 if (prev->instance == next->nest_lock)
3032 if (hlock_class(prev) != hlock_class(next))
3036 * Allow read-after-read recursion of the same
3037 * lock class (i.e. read_lock(lock)+read_lock(lock)):
3039 if ((next->read == 2) && prev->read)
3043 * We're holding the nest_lock, which serializes this lock's
3044 * nesting behaviour.
3049 print_deadlock_bug(curr, prev, next);
3056 * There was a chain-cache miss, and we are about to add a new dependency
3057 * to a previous lock. We validate the following rules:
3059 * - would the adding of the <prev> -> <next> dependency create a
3060 * circular dependency in the graph? [== circular deadlock]
3062 * - does the new prev->next dependency connect any hardirq-safe lock
3063 * (in the full backwards-subgraph starting at <prev>) with any
3064 * hardirq-unsafe lock (in the full forwards-subgraph starting at
3065 * <next>)? [== illegal lock inversion with hardirq contexts]
3067 * - does the new prev->next dependency connect any softirq-safe lock
3068 * (in the full backwards-subgraph starting at <prev>) with any
3069 * softirq-unsafe lock (in the full forwards-subgraph starting at
3070 * <next>)? [== illegal lock inversion with softirq contexts]
3072 * any of these scenarios could lead to a deadlock.
3074 * Then if all the validations pass, we add the forwards and backwards
3078 check_prev_add(struct task_struct *curr, struct held_lock *prev,
3079 struct held_lock *next, u16 distance,
3080 struct lock_trace **const trace)
3082 struct lock_list *entry;
3083 enum bfs_result ret;
3085 if (!hlock_class(prev)->key || !hlock_class(next)->key) {
3087 * The warning statements below may trigger a use-after-free
3088 * of the class name. It is better to trigger a use-after free
3089 * and to have the class name most of the time instead of not
3090 * having the class name available.
3092 WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
3093 "Detected use-after-free of lock class %px/%s\n",
3095 hlock_class(prev)->name);
3096 WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
3097 "Detected use-after-free of lock class %px/%s\n",
3099 hlock_class(next)->name);
3104 * Prove that the new <prev> -> <next> dependency would not
3105 * create a circular dependency in the graph. (We do this by
3106 * a breadth-first search into the graph starting at <next>,
3107 * and check whether we can reach <prev>.)
3109 * The search is limited by the size of the circular queue (i.e.,
3110 * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
3111 * in the graph whose neighbours are to be checked.
3113 ret = check_noncircular(next, prev, trace);
3114 if (unlikely(bfs_error(ret) || ret == BFS_RMATCH))
3117 if (!check_irq_usage(curr, prev, next))
3121 * Is the <prev> -> <next> dependency already present?
3123 * (this may occur even though this is a new chain: consider
3124 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
3125 * chains - the second one will be new, but L1 already has
3126 * L2 added to its dependency list, due to the first chain.)
3128 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
3129 if (entry->class == hlock_class(next)) {
3131 entry->distance = 1;
3132 entry->dep |= calc_dep(prev, next);
3135 * Also, update the reverse dependency in @next's
3136 * ->locks_before list.
3138 * Here we reuse @entry as the cursor, which is fine
3139 * because we won't go to the next iteration of the
3142 * For normal cases, we return in the inner loop.
3144 * If we fail to return, we have inconsistency, i.e.
3145 * <prev>::locks_after contains <next> while
3146 * <next>::locks_before doesn't contain <prev>. In
3147 * that case, we return after the inner and indicate
3148 * something is wrong.
3150 list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) {
3151 if (entry->class == hlock_class(prev)) {
3153 entry->distance = 1;
3154 entry->dep |= calc_depb(prev, next);
3159 /* <prev> is not found in <next>::locks_before */
3165 * Is the <prev> -> <next> link redundant?
3167 ret = check_redundant(prev, next);
3170 else if (ret == BFS_RMATCH)
3174 *trace = save_trace();
3180 * Ok, all validations passed, add the new lock
3181 * to the previous lock's dependency list:
3183 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
3184 &hlock_class(prev)->locks_after, distance,
3185 calc_dep(prev, next), *trace);
3190 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
3191 &hlock_class(next)->locks_before, distance,
3192 calc_depb(prev, next), *trace);
3200 * Add the dependency to all directly-previous locks that are 'relevant'.
3201 * The ones that are relevant are (in increasing distance from curr):
3202 * all consecutive trylock entries and the final non-trylock entry - or
3203 * the end of this context's lock-chain - whichever comes first.
3206 check_prevs_add(struct task_struct *curr, struct held_lock *next)
3208 struct lock_trace *trace = NULL;
3209 int depth = curr->lockdep_depth;
3210 struct held_lock *hlock;
3215 * Depth must not be zero for a non-head lock:
3220 * At least two relevant locks must exist for this
3223 if (curr->held_locks[depth].irq_context !=
3224 curr->held_locks[depth-1].irq_context)
3228 u16 distance = curr->lockdep_depth - depth + 1;
3229 hlock = curr->held_locks + depth - 1;
3232 int ret = check_prev_add(curr, hlock, next, distance, &trace);
3237 * Stop after the first non-trylock entry,
3238 * as non-trylock entries have added their
3239 * own direct dependencies already, so this
3240 * lock is connected to them indirectly:
3242 if (!hlock->trylock)
3248 * End of lock-stack?
3253 * Stop the search if we cross into another context:
3255 if (curr->held_locks[depth].irq_context !=
3256 curr->held_locks[depth-1].irq_context)
3261 if (!debug_locks_off_graph_unlock())
3265 * Clearly we all shouldn't be here, but since we made it we
3266 * can reliable say we messed up our state. See the above two
3267 * gotos for reasons why we could possibly end up here.
3274 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
3275 static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
3276 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
3277 unsigned long nr_zapped_lock_chains;
3278 unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */
3279 unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */
3280 unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */
3283 * The first 2 chain_hlocks entries in the chain block in the bucket
3284 * list contains the following meta data:
3287 * Bit 15 - always set to 1 (it is not a class index)
3288 * Bits 0-14 - upper 15 bits of the next block index
3289 * entry[1] - lower 16 bits of next block index
3291 * A next block index of all 1 bits means it is the end of the list.
3293 * On the unsized bucket (bucket-0), the 3rd and 4th entries contain
3294 * the chain block size:
3296 * entry[2] - upper 16 bits of the chain block size
3297 * entry[3] - lower 16 bits of the chain block size
3299 #define MAX_CHAIN_BUCKETS 16
3300 #define CHAIN_BLK_FLAG (1U << 15)
3301 #define CHAIN_BLK_LIST_END 0xFFFFU
3303 static int chain_block_buckets[MAX_CHAIN_BUCKETS];
3305 static inline int size_to_bucket(int size)
3307 if (size > MAX_CHAIN_BUCKETS)
3314 * Iterate all the chain blocks in a bucket.
3316 #define for_each_chain_block(bucket, prev, curr) \
3317 for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \
3319 (prev) = (curr), (curr) = chain_block_next(curr))
3324 static inline int chain_block_next(int offset)
3326 int next = chain_hlocks[offset];
3328 WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
3330 if (next == CHAIN_BLK_LIST_END)
3333 next &= ~CHAIN_BLK_FLAG;
3335 next |= chain_hlocks[offset + 1];
3343 static inline int chain_block_size(int offset)
3345 return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];
3348 static inline void init_chain_block(int offset, int next, int bucket, int size)
3350 chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG;
3351 chain_hlocks[offset + 1] = (u16)next;
3353 if (size && !bucket) {
3354 chain_hlocks[offset + 2] = size >> 16;
3355 chain_hlocks[offset + 3] = (u16)size;
3359 static inline void add_chain_block(int offset, int size)
3361 int bucket = size_to_bucket(size);
3362 int next = chain_block_buckets[bucket];
3365 if (unlikely(size < 2)) {
3367 * We can't store single entries on the freelist. Leak them.
3369 * One possible way out would be to uniquely mark them, other
3370 * than with CHAIN_BLK_FLAG, such that we can recover them when
3371 * the block before it is re-added.
3374 nr_lost_chain_hlocks++;
3378 nr_free_chain_hlocks += size;
3380 nr_large_chain_blocks++;
3383 * Variable sized, sort large to small.
3385 for_each_chain_block(0, prev, curr) {
3386 if (size >= chain_block_size(curr))
3389 init_chain_block(offset, curr, 0, size);
3391 chain_block_buckets[0] = offset;
3393 init_chain_block(prev, offset, 0, 0);
3397 * Fixed size, add to head.
3399 init_chain_block(offset, next, bucket, size);
3400 chain_block_buckets[bucket] = offset;
3404 * Only the first block in the list can be deleted.
3406 * For the variable size bucket[0], the first block (the largest one) is
3407 * returned, broken up and put back into the pool. So if a chain block of
3408 * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be
3409 * queued up after the primordial chain block and never be used until the
3410 * hlock entries in the primordial chain block is almost used up. That
3411 * causes fragmentation and reduce allocation efficiency. That can be
3412 * monitored by looking at the "large chain blocks" number in lockdep_stats.
3414 static inline void del_chain_block(int bucket, int size, int next)
3416 nr_free_chain_hlocks -= size;
3417 chain_block_buckets[bucket] = next;
3420 nr_large_chain_blocks--;
3423 static void init_chain_block_buckets(void)
3427 for (i = 0; i < MAX_CHAIN_BUCKETS; i++)
3428 chain_block_buckets[i] = -1;
3430 add_chain_block(0, ARRAY_SIZE(chain_hlocks));
3434 * Return offset of a chain block of the right size or -1 if not found.
3436 * Fairly simple worst-fit allocator with the addition of a number of size
3437 * specific free lists.
3439 static int alloc_chain_hlocks(int req)
3441 int bucket, curr, size;
3444 * We rely on the MSB to act as an escape bit to denote freelist
3445 * pointers. Make sure this bit isn't set in 'normal' class_idx usage.
3447 BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
3449 init_data_structures_once();
3451 if (nr_free_chain_hlocks < req)
3455 * We require a minimum of 2 (u16) entries to encode a freelist
3459 bucket = size_to_bucket(req);
3460 curr = chain_block_buckets[bucket];
3464 del_chain_block(bucket, req, chain_block_next(curr));
3468 curr = chain_block_buckets[0];
3472 * The variable sized freelist is sorted by size; the first entry is
3473 * the largest. Use it if it fits.
3476 size = chain_block_size(curr);
3477 if (likely(size >= req)) {
3478 del_chain_block(0, size, chain_block_next(curr));
3479 add_chain_block(curr + req, size - req);
3485 * Last resort, split a block in a larger sized bucket.
3487 for (size = MAX_CHAIN_BUCKETS; size > req; size--) {
3488 bucket = size_to_bucket(size);
3489 curr = chain_block_buckets[bucket];
3493 del_chain_block(bucket, size, chain_block_next(curr));
3494 add_chain_block(curr + req, size - req);
3501 static inline void free_chain_hlocks(int base, int size)
3503 add_chain_block(base, max(size, 2));
3506 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
3508 u16 chain_hlock = chain_hlocks[chain->base + i];
3509 unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
3511 return lock_classes + class_idx;
3515 * Returns the index of the first held_lock of the current chain
3517 static inline int get_first_held_lock(struct task_struct *curr,
3518 struct held_lock *hlock)
3521 struct held_lock *hlock_curr;
3523 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
3524 hlock_curr = curr->held_locks + i;
3525 if (hlock_curr->irq_context != hlock->irq_context)
3533 #ifdef CONFIG_DEBUG_LOCKDEP
3535 * Returns the next chain_key iteration
3537 static u64 print_chain_key_iteration(u16 hlock_id, u64 chain_key)
3539 u64 new_chain_key = iterate_chain_key(chain_key, hlock_id);
3541 printk(" hlock_id:%d -> chain_key:%016Lx",
3542 (unsigned int)hlock_id,
3543 (unsigned long long)new_chain_key);
3544 return new_chain_key;
3548 print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
3550 struct held_lock *hlock;
3551 u64 chain_key = INITIAL_CHAIN_KEY;
3552 int depth = curr->lockdep_depth;
3553 int i = get_first_held_lock(curr, hlock_next);
3555 printk("depth: %u (irq_context %u)\n", depth - i + 1,
3556 hlock_next->irq_context);
3557 for (; i < depth; i++) {
3558 hlock = curr->held_locks + i;
3559 chain_key = print_chain_key_iteration(hlock_id(hlock), chain_key);
3564 print_chain_key_iteration(hlock_id(hlock_next), chain_key);
3565 print_lock(hlock_next);
3568 static void print_chain_keys_chain(struct lock_chain *chain)
3571 u64 chain_key = INITIAL_CHAIN_KEY;
3574 printk("depth: %u\n", chain->depth);
3575 for (i = 0; i < chain->depth; i++) {
3576 hlock_id = chain_hlocks[chain->base + i];
3577 chain_key = print_chain_key_iteration(hlock_id, chain_key);
3579 print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id));
3584 static void print_collision(struct task_struct *curr,
3585 struct held_lock *hlock_next,
3586 struct lock_chain *chain)
3589 pr_warn("============================\n");
3590 pr_warn("WARNING: chain_key collision\n");
3591 print_kernel_ident();
3592 pr_warn("----------------------------\n");
3593 pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
3594 pr_warn("Hash chain already cached but the contents don't match!\n");
3596 pr_warn("Held locks:");
3597 print_chain_keys_held_locks(curr, hlock_next);
3599 pr_warn("Locks in cached chain:");
3600 print_chain_keys_chain(chain);
3602 pr_warn("\nstack backtrace:\n");
3608 * Checks whether the chain and the current held locks are consistent
3609 * in depth and also in content. If they are not it most likely means
3610 * that there was a collision during the calculation of the chain_key.
3611 * Returns: 0 not passed, 1 passed
3613 static int check_no_collision(struct task_struct *curr,
3614 struct held_lock *hlock,
3615 struct lock_chain *chain)
3617 #ifdef CONFIG_DEBUG_LOCKDEP
3620 i = get_first_held_lock(curr, hlock);
3622 if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
3623 print_collision(curr, hlock, chain);
3627 for (j = 0; j < chain->depth - 1; j++, i++) {
3628 id = hlock_id(&curr->held_locks[i]);
3630 if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
3631 print_collision(curr, hlock, chain);
3640 * Given an index that is >= -1, return the index of the next lock chain.
3641 * Return -2 if there is no next lock chain.
3643 long lockdep_next_lockchain(long i)
3645 i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
3646 return i < ARRAY_SIZE(lock_chains) ? i : -2;
3649 unsigned long lock_chain_count(void)
3651 return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
3654 /* Must be called with the graph lock held. */
3655 static struct lock_chain *alloc_lock_chain(void)
3657 int idx = find_first_zero_bit(lock_chains_in_use,
3658 ARRAY_SIZE(lock_chains));
3660 if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
3662 __set_bit(idx, lock_chains_in_use);
3663 return lock_chains + idx;
3667 * Adds a dependency chain into chain hashtable. And must be called with
3670 * Return 0 if fail, and graph_lock is released.
3671 * Return 1 if succeed, with graph_lock held.
3673 static inline int add_chain_cache(struct task_struct *curr,
3674 struct held_lock *hlock,
3677 struct hlist_head *hash_head = chainhashentry(chain_key);
3678 struct lock_chain *chain;
3682 * The caller must hold the graph lock, ensure we've got IRQs
3683 * disabled to make this an IRQ-safe lock.. for recursion reasons
3684 * lockdep won't complain about its own locking errors.
3686 if (lockdep_assert_locked())
3689 chain = alloc_lock_chain();
3691 if (!debug_locks_off_graph_unlock())
3694 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
3698 chain->chain_key = chain_key;
3699 chain->irq_context = hlock->irq_context;
3700 i = get_first_held_lock(curr, hlock);
3701 chain->depth = curr->lockdep_depth + 1 - i;
3703 BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
3704 BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
3705 BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
3707 j = alloc_chain_hlocks(chain->depth);
3709 if (!debug_locks_off_graph_unlock())
3712 print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
3718 for (j = 0; j < chain->depth - 1; j++, i++) {
3719 int lock_id = hlock_id(curr->held_locks + i);
3721 chain_hlocks[chain->base + j] = lock_id;
3723 chain_hlocks[chain->base + j] = hlock_id(hlock);
3724 hlist_add_head_rcu(&chain->entry, hash_head);
3725 debug_atomic_inc(chain_lookup_misses);
3726 inc_chains(chain->irq_context);
3732 * Look up a dependency chain. Must be called with either the graph lock or
3733 * the RCU read lock held.
3735 static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
3737 struct hlist_head *hash_head = chainhashentry(chain_key);
3738 struct lock_chain *chain;
3740 hlist_for_each_entry_rcu(chain, hash_head, entry) {
3741 if (READ_ONCE(chain->chain_key) == chain_key) {
3742 debug_atomic_inc(chain_lookup_hits);
3750 * If the key is not present yet in dependency chain cache then
3751 * add it and return 1 - in this case the new dependency chain is
3752 * validated. If the key is already hashed, return 0.
3753 * (On return with 1 graph_lock is held.)
3755 static inline int lookup_chain_cache_add(struct task_struct *curr,
3756 struct held_lock *hlock,
3759 struct lock_class *class = hlock_class(hlock);
3760 struct lock_chain *chain = lookup_chain_cache(chain_key);
3764 if (!check_no_collision(curr, hlock, chain))
3767 if (very_verbose(class)) {
3768 printk("\nhash chain already cached, key: "
3769 "%016Lx tail class: [%px] %s\n",
3770 (unsigned long long)chain_key,
3771 class->key, class->name);
3777 if (very_verbose(class)) {
3778 printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
3779 (unsigned long long)chain_key, class->key, class->name);
3786 * We have to walk the chain again locked - to avoid duplicates:
3788 chain = lookup_chain_cache(chain_key);
3794 if (!add_chain_cache(curr, hlock, chain_key))
3800 static int validate_chain(struct task_struct *curr,
3801 struct held_lock *hlock,
3802 int chain_head, u64 chain_key)
3805 * Trylock needs to maintain the stack of held locks, but it
3806 * does not add new dependencies, because trylock can be done
3809 * We look up the chain_key and do the O(N^2) check and update of
3810 * the dependencies only if this is a new dependency chain.
3811 * (If lookup_chain_cache_add() return with 1 it acquires
3812 * graph_lock for us)
3814 if (!hlock->trylock && hlock->check &&
3815 lookup_chain_cache_add(curr, hlock, chain_key)) {
3817 * Check whether last held lock:
3819 * - is irq-safe, if this lock is irq-unsafe
3820 * - is softirq-safe, if this lock is hardirq-unsafe
3822 * And check whether the new lock's dependency graph
3823 * could lead back to the previous lock:
3825 * - within the current held-lock stack
3826 * - across our accumulated lock dependency records
3828 * any of these scenarios could lead to a deadlock.
3831 * The simple case: does the current hold the same lock
3834 int ret = check_deadlock(curr, hlock);
3839 * Add dependency only if this lock is not the head
3840 * of the chain, and if the new lock introduces no more
3841 * lock dependency (because we already hold a lock with the
3842 * same lock class) nor deadlock (because the nest_lock
3843 * serializes nesting locks), see the comments for
3846 if (!chain_head && ret != 2) {
3847 if (!check_prevs_add(curr, hlock))
3853 /* after lookup_chain_cache_add(): */
3854 if (unlikely(!debug_locks))
3861 static inline int validate_chain(struct task_struct *curr,
3862 struct held_lock *hlock,
3863 int chain_head, u64 chain_key)
3868 static void init_chain_block_buckets(void) { }
3869 #endif /* CONFIG_PROVE_LOCKING */
3872 * We are building curr_chain_key incrementally, so double-check
3873 * it from scratch, to make sure that it's done correctly:
3875 static void check_chain_key(struct task_struct *curr)
3877 #ifdef CONFIG_DEBUG_LOCKDEP
3878 struct held_lock *hlock, *prev_hlock = NULL;
3880 u64 chain_key = INITIAL_CHAIN_KEY;
3882 for (i = 0; i < curr->lockdep_depth; i++) {
3883 hlock = curr->held_locks + i;
3884 if (chain_key != hlock->prev_chain_key) {
3887 * We got mighty confused, our chain keys don't match
3888 * with what we expect, someone trample on our task state?
3890 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
3891 curr->lockdep_depth, i,
3892 (unsigned long long)chain_key,
3893 (unsigned long long)hlock->prev_chain_key);
3898 * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is
3899 * it registered lock class index?
3901 if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use)))
3904 if (prev_hlock && (prev_hlock->irq_context !=
3905 hlock->irq_context))
3906 chain_key = INITIAL_CHAIN_KEY;
3907 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
3910 if (chain_key != curr->curr_chain_key) {
3913 * More smoking hash instead of calculating it, damn see these
3914 * numbers float.. I bet that a pink elephant stepped on my memory.
3916 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
3917 curr->lockdep_depth, i,
3918 (unsigned long long)chain_key,
3919 (unsigned long long)curr->curr_chain_key);
3924 #ifdef CONFIG_PROVE_LOCKING
3925 static int mark_lock(struct task_struct *curr, struct held_lock *this,
3926 enum lock_usage_bit new_bit);
3928 static void print_usage_bug_scenario(struct held_lock *lock)
3930 struct lock_class *class = hlock_class(lock);
3932 printk(" Possible unsafe locking scenario:\n\n");
3936 __print_lock_name(class);
3937 printk(KERN_CONT ");\n");
3938 printk(" <Interrupt>\n");
3940 __print_lock_name(class);
3941 printk(KERN_CONT ");\n");
3942 printk("\n *** DEADLOCK ***\n\n");
3946 print_usage_bug(struct task_struct *curr, struct held_lock *this,
3947 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
3949 if (!debug_locks_off() || debug_locks_silent)
3953 pr_warn("================================\n");
3954 pr_warn("WARNING: inconsistent lock state\n");
3955 print_kernel_ident();
3956 pr_warn("--------------------------------\n");
3958 pr_warn("inconsistent {%s} -> {%s} usage.\n",
3959 usage_str[prev_bit], usage_str[new_bit]);
3961 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
3962 curr->comm, task_pid_nr(curr),
3963 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
3964 lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
3965 lockdep_hardirqs_enabled(),
3966 lockdep_softirqs_enabled(curr));
3969 pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
3970 print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
3972 print_irqtrace_events(curr);
3973 pr_warn("\nother info that might help us debug this:\n");
3974 print_usage_bug_scenario(this);
3976 lockdep_print_held_locks(curr);
3978 pr_warn("\nstack backtrace:\n");
3983 * Print out an error if an invalid bit is set:
3986 valid_state(struct task_struct *curr, struct held_lock *this,
3987 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
3989 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
3991 print_usage_bug(curr, this, bad_bit, new_bit);
3999 * print irq inversion bug:
4002 print_irq_inversion_bug(struct task_struct *curr,
4003 struct lock_list *root, struct lock_list *other,
4004 struct held_lock *this, int forwards,
4005 const char *irqclass)
4007 struct lock_list *entry = other;
4008 struct lock_list *middle = NULL;
4011 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
4015 pr_warn("========================================================\n");
4016 pr_warn("WARNING: possible irq lock inversion dependency detected\n");
4017 print_kernel_ident();
4018 pr_warn("--------------------------------------------------------\n");
4019 pr_warn("%s/%d just changed the state of lock:\n",
4020 curr->comm, task_pid_nr(curr));
4023 pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
4025 pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
4026 print_lock_name(other->class);
4027 pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
4029 pr_warn("\nother info that might help us debug this:\n");
4031 /* Find a middle lock (if one exists) */
4032 depth = get_lock_depth(other);
4034 if (depth == 0 && (entry != root)) {
4035 pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
4039 entry = get_lock_parent(entry);
4041 } while (entry && entry != root && (depth >= 0));
4043 print_irq_lock_scenario(root, other,
4044 middle ? middle->class : root->class, other->class);
4046 print_irq_lock_scenario(other, root,
4047 middle ? middle->class : other->class, root->class);
4049 lockdep_print_held_locks(curr);
4051 pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
4052 root->trace = save_trace();
4055 print_shortest_lock_dependencies(other, root);
4057 pr_warn("\nstack backtrace:\n");
4062 * Prove that in the forwards-direction subgraph starting at <this>
4063 * there is no lock matching <mask>:
4066 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
4067 enum lock_usage_bit bit)
4069 enum bfs_result ret;
4070 struct lock_list root;
4071 struct lock_list *target_entry;
4072 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4073 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4075 bfs_init_root(&root, this);
4076 ret = find_usage_forwards(&root, usage_mask, &target_entry);
4077 if (bfs_error(ret)) {
4081 if (ret == BFS_RNOMATCH)
4084 /* Check whether write or read usage is the match */
4085 if (target_entry->class->usage_mask & lock_flag(bit)) {
4086 print_irq_inversion_bug(curr, &root, target_entry,
4087 this, 1, state_name(bit));
4089 print_irq_inversion_bug(curr, &root, target_entry,
4090 this, 1, state_name(read_bit));
4097 * Prove that in the backwards-direction subgraph starting at <this>
4098 * there is no lock matching <mask>:
4101 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
4102 enum lock_usage_bit bit)
4104 enum bfs_result ret;
4105 struct lock_list root;
4106 struct lock_list *target_entry;
4107 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4108 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4110 bfs_init_rootb(&root, this);
4111 ret = find_usage_backwards(&root, usage_mask, &target_entry);
4112 if (bfs_error(ret)) {
4116 if (ret == BFS_RNOMATCH)
4119 /* Check whether write or read usage is the match */
4120 if (target_entry->class->usage_mask & lock_flag(bit)) {
4121 print_irq_inversion_bug(curr, &root, target_entry,
4122 this, 0, state_name(bit));
4124 print_irq_inversion_bug(curr, &root, target_entry,
4125 this, 0, state_name(read_bit));
4131 void print_irqtrace_events(struct task_struct *curr)
4133 const struct irqtrace_events *trace = &curr->irqtrace;
4135 printk("irq event stamp: %u\n", trace->irq_events);
4136 printk("hardirqs last enabled at (%u): [<%px>] %pS\n",
4137 trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
4138 (void *)trace->hardirq_enable_ip);
4139 printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
4140 trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip,
4141 (void *)trace->hardirq_disable_ip);
4142 printk("softirqs last enabled at (%u): [<%px>] %pS\n",
4143 trace->softirq_enable_event, (void *)trace->softirq_enable_ip,
4144 (void *)trace->softirq_enable_ip);
4145 printk("softirqs last disabled at (%u): [<%px>] %pS\n",
4146 trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
4147 (void *)trace->softirq_disable_ip);
4150 static int HARDIRQ_verbose(struct lock_class *class)
4153 return class_filter(class);
4158 static int SOFTIRQ_verbose(struct lock_class *class)
4161 return class_filter(class);
4166 static int (*state_verbose_f[])(struct lock_class *class) = {
4167 #define LOCKDEP_STATE(__STATE) \
4169 #include "lockdep_states.h"
4170 #undef LOCKDEP_STATE
4173 static inline int state_verbose(enum lock_usage_bit bit,
4174 struct lock_class *class)
4176 return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
4179 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
4180 enum lock_usage_bit bit, const char *name);
4183 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
4184 enum lock_usage_bit new_bit)
4186 int excl_bit = exclusive_bit(new_bit);
4187 int read = new_bit & LOCK_USAGE_READ_MASK;
4188 int dir = new_bit & LOCK_USAGE_DIR_MASK;
4191 * Validate that this particular lock does not have conflicting
4194 if (!valid_state(curr, this, new_bit, excl_bit))
4198 * Check for read in write conflicts
4200 if (!read && !valid_state(curr, this, new_bit,
4201 excl_bit + LOCK_USAGE_READ_MASK))
4206 * Validate that the lock dependencies don't have conflicting usage
4211 * mark ENABLED has to look backwards -- to ensure no dependee
4212 * has USED_IN state, which, again, would allow recursion deadlocks.
4214 if (!check_usage_backwards(curr, this, excl_bit))
4218 * mark USED_IN has to look forwards -- to ensure no dependency
4219 * has ENABLED state, which would allow recursion deadlocks.
4221 if (!check_usage_forwards(curr, this, excl_bit))
4225 if (state_verbose(new_bit, hlock_class(this)))
4232 * Mark all held locks with a usage bit:
4235 mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
4237 struct held_lock *hlock;
4240 for (i = 0; i < curr->lockdep_depth; i++) {
4241 enum lock_usage_bit hlock_bit = base_bit;
4242 hlock = curr->held_locks + i;
4245 hlock_bit += LOCK_USAGE_READ_MASK;
4247 BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
4252 if (!mark_lock(curr, hlock, hlock_bit))
4260 * Hardirqs will be enabled:
4262 static void __trace_hardirqs_on_caller(void)
4264 struct task_struct *curr = current;
4267 * We are going to turn hardirqs on, so set the
4268 * usage bit for all held locks:
4270 if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
4273 * If we have softirqs enabled, then set the usage
4274 * bit for all held locks. (disabled hardirqs prevented
4275 * this bit from being set before)
4277 if (curr->softirqs_enabled)
4278 mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
4282 * lockdep_hardirqs_on_prepare - Prepare for enabling interrupts
4284 * Invoked before a possible transition to RCU idle from exit to user or
4285 * guest mode. This ensures that all RCU operations are done before RCU
4286 * stops watching. After the RCU transition lockdep_hardirqs_on() has to be
4287 * invoked to set the final state.
4289 void lockdep_hardirqs_on_prepare(void)
4291 if (unlikely(!debug_locks))
4295 * NMIs do not (and cannot) track lock dependencies, nothing to do.
4297 if (unlikely(in_nmi()))
4300 if (unlikely(this_cpu_read(lockdep_recursion)))
4303 if (unlikely(lockdep_hardirqs_enabled())) {
4305 * Neither irq nor preemption are disabled here
4306 * so this is racy by nature but losing one hit
4307 * in a stat is not a big deal.
4309 __debug_atomic_inc(redundant_hardirqs_on);
4314 * We're enabling irqs and according to our state above irqs weren't
4315 * already enabled, yet we find the hardware thinks they are in fact
4316 * enabled.. someone messed up their IRQ state tracing.
4318 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4322 * See the fine text that goes along with this variable definition.
4324 if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
4328 * Can't allow enabling interrupts while in an interrupt handler,
4329 * that's general bad form and such. Recursion, limited stack etc..
4331 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context()))
4334 current->hardirq_chain_key = current->curr_chain_key;
4336 lockdep_recursion_inc();
4337 __trace_hardirqs_on_caller();
4338 lockdep_recursion_finish();
4340 EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
4342 void noinstr lockdep_hardirqs_on(unsigned long ip)
4344 struct irqtrace_events *trace = ¤t->irqtrace;
4346 if (unlikely(!debug_locks))
4350 * NMIs can happen in the middle of local_irq_{en,dis}able() where the
4351 * tracking state and hardware state are out of sync.
4353 * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from,
4354 * and not rely on hardware state like normal interrupts.
4356 if (unlikely(in_nmi())) {
4357 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4362 * - recursion check, because NMI can hit lockdep;
4363 * - hardware state check, because above;
4364 * - chain_key check, see lockdep_hardirqs_on_prepare().
4369 if (unlikely(this_cpu_read(lockdep_recursion)))
4372 if (lockdep_hardirqs_enabled()) {
4374 * Neither irq nor preemption are disabled here
4375 * so this is racy by nature but losing one hit
4376 * in a stat is not a big deal.
4378 __debug_atomic_inc(redundant_hardirqs_on);
4383 * We're enabling irqs and according to our state above irqs weren't
4384 * already enabled, yet we find the hardware thinks they are in fact
4385 * enabled.. someone messed up their IRQ state tracing.
4387 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4391 * Ensure the lock stack remained unchanged between
4392 * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().
4394 DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key !=
4395 current->curr_chain_key);
4398 /* we'll do an OFF -> ON transition: */
4399 __this_cpu_write(hardirqs_enabled, 1);
4400 trace->hardirq_enable_ip = ip;
4401 trace->hardirq_enable_event = ++trace->irq_events;
4402 debug_atomic_inc(hardirqs_on_events);
4404 EXPORT_SYMBOL_GPL(lockdep_hardirqs_on);
4407 * Hardirqs were disabled:
4409 void noinstr lockdep_hardirqs_off(unsigned long ip)
4411 if (unlikely(!debug_locks))
4415 * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep;
4416 * they will restore the software state. This ensures the software
4417 * state is consistent inside NMIs as well.
4420 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4422 } else if (__this_cpu_read(lockdep_recursion))
4426 * So we're supposed to get called after you mask local IRQs, but for
4427 * some reason the hardware doesn't quite think you did a proper job.
4429 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4432 if (lockdep_hardirqs_enabled()) {
4433 struct irqtrace_events *trace = ¤t->irqtrace;
4436 * We have done an ON -> OFF transition:
4438 __this_cpu_write(hardirqs_enabled, 0);
4439 trace->hardirq_disable_ip = ip;
4440 trace->hardirq_disable_event = ++trace->irq_events;
4441 debug_atomic_inc(hardirqs_off_events);
4443 debug_atomic_inc(redundant_hardirqs_off);
4446 EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
4449 * Softirqs will be enabled:
4451 void lockdep_softirqs_on(unsigned long ip)
4453 struct irqtrace_events *trace = ¤t->irqtrace;
4455 if (unlikely(!lockdep_enabled()))
4459 * We fancy IRQs being disabled here, see softirq.c, avoids
4460 * funny state and nesting things.
4462 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4465 if (current->softirqs_enabled) {
4466 debug_atomic_inc(redundant_softirqs_on);
4470 lockdep_recursion_inc();
4472 * We'll do an OFF -> ON transition:
4474 current->softirqs_enabled = 1;
4475 trace->softirq_enable_ip = ip;
4476 trace->softirq_enable_event = ++trace->irq_events;
4477 debug_atomic_inc(softirqs_on_events);
4479 * We are going to turn softirqs on, so set the
4480 * usage bit for all held locks, if hardirqs are
4483 if (lockdep_hardirqs_enabled())
4484 mark_held_locks(current, LOCK_ENABLED_SOFTIRQ);
4485 lockdep_recursion_finish();
4489 * Softirqs were disabled:
4491 void lockdep_softirqs_off(unsigned long ip)
4493 if (unlikely(!lockdep_enabled()))
4497 * We fancy IRQs being disabled here, see softirq.c
4499 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4502 if (current->softirqs_enabled) {
4503 struct irqtrace_events *trace = ¤t->irqtrace;
4506 * We have done an ON -> OFF transition:
4508 current->softirqs_enabled = 0;
4509 trace->softirq_disable_ip = ip;
4510 trace->softirq_disable_event = ++trace->irq_events;
4511 debug_atomic_inc(softirqs_off_events);
4513 * Whoops, we wanted softirqs off, so why aren't they?
4515 DEBUG_LOCKS_WARN_ON(!softirq_count());
4517 debug_atomic_inc(redundant_softirqs_off);
4521 mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4527 * If non-trylock use in a hardirq or softirq context, then
4528 * mark the lock as used in these contexts:
4530 if (!hlock->trylock) {
4532 if (lockdep_hardirq_context())
4533 if (!mark_lock(curr, hlock,
4534 LOCK_USED_IN_HARDIRQ_READ))
4536 if (curr->softirq_context)
4537 if (!mark_lock(curr, hlock,
4538 LOCK_USED_IN_SOFTIRQ_READ))
4541 if (lockdep_hardirq_context())
4542 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
4544 if (curr->softirq_context)
4545 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
4551 * For lock_sync(), don't mark the ENABLED usage, since lock_sync()
4552 * creates no critical section and no extra dependency can be introduced
4555 if (!hlock->hardirqs_off && !hlock->sync) {
4557 if (!mark_lock(curr, hlock,
4558 LOCK_ENABLED_HARDIRQ_READ))
4560 if (curr->softirqs_enabled)
4561 if (!mark_lock(curr, hlock,
4562 LOCK_ENABLED_SOFTIRQ_READ))
4565 if (!mark_lock(curr, hlock,
4566 LOCK_ENABLED_HARDIRQ))
4568 if (curr->softirqs_enabled)
4569 if (!mark_lock(curr, hlock,
4570 LOCK_ENABLED_SOFTIRQ))
4576 /* mark it as used: */
4577 if (!mark_lock(curr, hlock, LOCK_USED))
4583 static inline unsigned int task_irq_context(struct task_struct *task)
4585 return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() +
4586 LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;
4589 static int separate_irq_context(struct task_struct *curr,
4590 struct held_lock *hlock)
4592 unsigned int depth = curr->lockdep_depth;
4595 * Keep track of points where we cross into an interrupt context:
4598 struct held_lock *prev_hlock;
4600 prev_hlock = curr->held_locks + depth-1;
4602 * If we cross into another context, reset the
4603 * hash key (this also prevents the checking and the
4604 * adding of the dependency to 'prev'):
4606 if (prev_hlock->irq_context != hlock->irq_context)
4613 * Mark a lock with a usage bit, and validate the state transition:
4615 static int mark_lock(struct task_struct *curr, struct held_lock *this,
4616 enum lock_usage_bit new_bit)
4618 unsigned int new_mask, ret = 1;
4620 if (new_bit >= LOCK_USAGE_STATES) {
4621 DEBUG_LOCKS_WARN_ON(1);
4625 if (new_bit == LOCK_USED && this->read)
4626 new_bit = LOCK_USED_READ;
4628 new_mask = 1 << new_bit;
4631 * If already set then do not dirty the cacheline,
4632 * nor do any checks:
4634 if (likely(hlock_class(this)->usage_mask & new_mask))
4640 * Make sure we didn't race:
4642 if (unlikely(hlock_class(this)->usage_mask & new_mask))
4645 if (!hlock_class(this)->usage_mask)
4646 debug_atomic_dec(nr_unused_locks);
4648 hlock_class(this)->usage_mask |= new_mask;
4650 if (new_bit < LOCK_TRACE_STATES) {
4651 if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
4655 if (new_bit < LOCK_USED) {
4656 ret = mark_lock_irq(curr, this, new_bit);
4665 * We must printk outside of the graph_lock:
4668 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
4670 print_irqtrace_events(curr);
4677 static inline short task_wait_context(struct task_struct *curr)
4680 * Set appropriate wait type for the context; for IRQs we have to take
4681 * into account force_irqthread as that is implied by PREEMPT_RT.
4683 if (lockdep_hardirq_context()) {
4685 * Check if force_irqthreads will run us threaded.
4687 if (curr->hardirq_threaded || curr->irq_config)
4688 return LD_WAIT_CONFIG;
4690 return LD_WAIT_SPIN;
4691 } else if (curr->softirq_context) {
4693 * Softirqs are always threaded.
4695 return LD_WAIT_CONFIG;
4702 print_lock_invalid_wait_context(struct task_struct *curr,
4703 struct held_lock *hlock)
4707 if (!debug_locks_off())
4709 if (debug_locks_silent)
4713 pr_warn("=============================\n");
4714 pr_warn("[ BUG: Invalid wait context ]\n");
4715 print_kernel_ident();
4716 pr_warn("-----------------------------\n");
4718 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4721 pr_warn("other info that might help us debug this:\n");
4723 curr_inner = task_wait_context(curr);
4724 pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
4726 lockdep_print_held_locks(curr);
4728 pr_warn("stack backtrace:\n");
4735 * Verify the wait_type context.
4737 * This check validates we take locks in the right wait-type order; that is it
4738 * ensures that we do not take mutexes inside spinlocks and do not attempt to
4739 * acquire spinlocks inside raw_spinlocks and the sort.
4741 * The entire thing is slightly more complex because of RCU, RCU is a lock that
4742 * can be taken from (pretty much) any context but also has constraints.
4743 * However when taken in a stricter environment the RCU lock does not loosen
4746 * Therefore we must look for the strictest environment in the lock stack and
4747 * compare that to the lock we're trying to acquire.
4749 static int check_wait_context(struct task_struct *curr, struct held_lock *next)
4751 u8 next_inner = hlock_class(next)->wait_type_inner;
4752 u8 next_outer = hlock_class(next)->wait_type_outer;
4756 if (!next_inner || next->trylock)
4760 next_outer = next_inner;
4763 * Find start of current irq_context..
4765 for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
4766 struct held_lock *prev = curr->held_locks + depth;
4767 if (prev->irq_context != next->irq_context)
4772 curr_inner = task_wait_context(curr);
4774 for (; depth < curr->lockdep_depth; depth++) {
4775 struct held_lock *prev = curr->held_locks + depth;
4776 struct lock_class *class = hlock_class(prev);
4777 u8 prev_inner = class->wait_type_inner;
4781 * We can have a bigger inner than a previous one
4782 * when outer is smaller than inner, as with RCU.
4784 * Also due to trylocks.
4786 curr_inner = min(curr_inner, prev_inner);
4789 * Allow override for annotations -- this is typically
4790 * only valid/needed for code that only exists when
4791 * CONFIG_PREEMPT_RT=n.
4793 if (unlikely(class->lock_type == LD_LOCK_WAIT_OVERRIDE))
4794 curr_inner = prev_inner;
4798 if (next_outer > curr_inner)
4799 return print_lock_invalid_wait_context(curr, next);
4804 #else /* CONFIG_PROVE_LOCKING */
4807 mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4812 static inline unsigned int task_irq_context(struct task_struct *task)
4817 static inline int separate_irq_context(struct task_struct *curr,
4818 struct held_lock *hlock)
4823 static inline int check_wait_context(struct task_struct *curr,
4824 struct held_lock *next)
4829 #endif /* CONFIG_PROVE_LOCKING */
4832 * Initialize a lock instance's lock-class mapping info:
4834 void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
4835 struct lock_class_key *key, int subclass,
4836 u8 inner, u8 outer, u8 lock_type)
4840 for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
4841 lock->class_cache[i] = NULL;
4843 #ifdef CONFIG_LOCK_STAT
4844 lock->cpu = raw_smp_processor_id();
4848 * Can't be having no nameless bastards around this place!
4850 if (DEBUG_LOCKS_WARN_ON(!name)) {
4851 lock->name = "NULL";
4857 lock->wait_type_outer = outer;
4858 lock->wait_type_inner = inner;
4859 lock->lock_type = lock_type;
4862 * No key, no joy, we need to hash something.
4864 if (DEBUG_LOCKS_WARN_ON(!key))
4867 * Sanity check, the lock-class key must either have been allocated
4868 * statically or must have been registered as a dynamic key.
4870 if (!static_obj(key) && !is_dynamic_key(key)) {
4872 printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
4873 DEBUG_LOCKS_WARN_ON(1);
4878 if (unlikely(!debug_locks))
4882 unsigned long flags;
4884 if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled()))
4887 raw_local_irq_save(flags);
4888 lockdep_recursion_inc();
4889 register_lock_class(lock, subclass, 1);
4890 lockdep_recursion_finish();
4891 raw_local_irq_restore(flags);
4894 EXPORT_SYMBOL_GPL(lockdep_init_map_type);
4896 struct lock_class_key __lockdep_no_validate__;
4897 EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
4900 print_lock_nested_lock_not_held(struct task_struct *curr,
4901 struct held_lock *hlock)
4903 if (!debug_locks_off())
4905 if (debug_locks_silent)
4909 pr_warn("==================================\n");
4910 pr_warn("WARNING: Nested lock was not taken\n");
4911 print_kernel_ident();
4912 pr_warn("----------------------------------\n");
4914 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4917 pr_warn("\nbut this task is not holding:\n");
4918 pr_warn("%s\n", hlock->nest_lock->name);
4920 pr_warn("\nstack backtrace:\n");
4923 pr_warn("\nother info that might help us debug this:\n");
4924 lockdep_print_held_locks(curr);
4926 pr_warn("\nstack backtrace:\n");
4930 static int __lock_is_held(const struct lockdep_map *lock, int read);
4933 * This gets called for every mutex_lock*()/spin_lock*() operation.
4934 * We maintain the dependency maps and validate the locking attempt:
4936 * The callers must make sure that IRQs are disabled before calling it,
4937 * otherwise we could get an interrupt which would want to take locks,
4938 * which would end up in lockdep again.
4940 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
4941 int trylock, int read, int check, int hardirqs_off,
4942 struct lockdep_map *nest_lock, unsigned long ip,
4943 int references, int pin_count, int sync)
4945 struct task_struct *curr = current;
4946 struct lock_class *class = NULL;
4947 struct held_lock *hlock;
4953 if (unlikely(!debug_locks))
4956 if (!prove_locking || lock->key == &__lockdep_no_validate__)
4959 if (subclass < NR_LOCKDEP_CACHING_CLASSES)
4960 class = lock->class_cache[subclass];
4964 if (unlikely(!class)) {
4965 class = register_lock_class(lock, subclass, 0);
4970 debug_class_ops_inc(class);
4972 if (very_verbose(class)) {
4973 printk("\nacquire class [%px] %s", class->key, class->name);
4974 if (class->name_version > 1)
4975 printk(KERN_CONT "#%d", class->name_version);
4976 printk(KERN_CONT "\n");
4981 * Add the lock to the list of currently held locks.
4982 * (we dont increase the depth just yet, up until the
4983 * dependency checks are done)
4985 depth = curr->lockdep_depth;
4987 * Ran out of static storage for our per-task lock stack again have we?
4989 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
4992 class_idx = class - lock_classes;
4994 if (depth && !sync) {
4995 /* we're holding locks and the new held lock is not a sync */
4996 hlock = curr->held_locks + depth - 1;
4997 if (hlock->class_idx == class_idx && nest_lock) {
5001 if (!hlock->references)
5002 hlock->references++;
5004 hlock->references += references;
5007 if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
5014 hlock = curr->held_locks + depth;
5016 * Plain impossible, we just registered it and checked it weren't no
5017 * NULL like.. I bet this mushroom I ate was good!
5019 if (DEBUG_LOCKS_WARN_ON(!class))
5021 hlock->class_idx = class_idx;
5022 hlock->acquire_ip = ip;
5023 hlock->instance = lock;
5024 hlock->nest_lock = nest_lock;
5025 hlock->irq_context = task_irq_context(curr);
5026 hlock->trylock = trylock;
5028 hlock->check = check;
5029 hlock->sync = !!sync;
5030 hlock->hardirqs_off = !!hardirqs_off;
5031 hlock->references = references;
5032 #ifdef CONFIG_LOCK_STAT
5033 hlock->waittime_stamp = 0;
5034 hlock->holdtime_stamp = lockstat_clock();
5036 hlock->pin_count = pin_count;
5038 if (check_wait_context(curr, hlock))
5041 /* Initialize the lock usage bit */
5042 if (!mark_usage(curr, hlock, check))
5046 * Calculate the chain hash: it's the combined hash of all the
5047 * lock keys along the dependency chain. We save the hash value
5048 * at every step so that we can get the current hash easily
5049 * after unlock. The chain hash is then used to cache dependency
5052 * The 'key ID' is what is the most compact key value to drive
5053 * the hash, not class->key.
5056 * Whoops, we did it again.. class_idx is invalid.
5058 if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use)))
5061 chain_key = curr->curr_chain_key;
5064 * How can we have a chain hash when we ain't got no keys?!
5066 if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
5071 hlock->prev_chain_key = chain_key;
5072 if (separate_irq_context(curr, hlock)) {
5073 chain_key = INITIAL_CHAIN_KEY;
5076 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
5078 if (nest_lock && !__lock_is_held(nest_lock, -1)) {
5079 print_lock_nested_lock_not_held(curr, hlock);
5083 if (!debug_locks_silent) {
5084 WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key);
5085 WARN_ON_ONCE(!hlock_class(hlock)->key);
5088 if (!validate_chain(curr, hlock, chain_head, chain_key))
5091 /* For lock_sync(), we are done here since no actual critical section */
5095 curr->curr_chain_key = chain_key;
5096 curr->lockdep_depth++;
5097 check_chain_key(curr);
5098 #ifdef CONFIG_DEBUG_LOCKDEP
5099 if (unlikely(!debug_locks))
5102 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
5104 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
5105 printk(KERN_DEBUG "depth: %i max: %lu!\n",
5106 curr->lockdep_depth, MAX_LOCK_DEPTH);
5108 lockdep_print_held_locks(current);
5109 debug_show_all_locks();
5115 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
5116 max_lockdep_depth = curr->lockdep_depth;
5121 static void print_unlock_imbalance_bug(struct task_struct *curr,
5122 struct lockdep_map *lock,
5125 if (!debug_locks_off())
5127 if (debug_locks_silent)
5131 pr_warn("=====================================\n");
5132 pr_warn("WARNING: bad unlock balance detected!\n");
5133 print_kernel_ident();
5134 pr_warn("-------------------------------------\n");
5135 pr_warn("%s/%d is trying to release lock (",
5136 curr->comm, task_pid_nr(curr));
5137 print_lockdep_cache(lock);
5139 print_ip_sym(KERN_WARNING, ip);
5140 pr_warn("but there are no more locks to release!\n");
5141 pr_warn("\nother info that might help us debug this:\n");
5142 lockdep_print_held_locks(curr);
5144 pr_warn("\nstack backtrace:\n");
5148 static noinstr int match_held_lock(const struct held_lock *hlock,
5149 const struct lockdep_map *lock)
5151 if (hlock->instance == lock)
5154 if (hlock->references) {
5155 const struct lock_class *class = lock->class_cache[0];
5158 class = look_up_lock_class(lock, 0);
5161 * If look_up_lock_class() failed to find a class, we're trying
5162 * to test if we hold a lock that has never yet been acquired.
5163 * Clearly if the lock hasn't been acquired _ever_, we're not
5164 * holding it either, so report failure.
5170 * References, but not a lock we're actually ref-counting?
5171 * State got messed up, follow the sites that change ->references
5172 * and try to make sense of it.
5174 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
5177 if (hlock->class_idx == class - lock_classes)
5184 /* @depth must not be zero */
5185 static struct held_lock *find_held_lock(struct task_struct *curr,
5186 struct lockdep_map *lock,
5187 unsigned int depth, int *idx)
5189 struct held_lock *ret, *hlock, *prev_hlock;
5193 hlock = curr->held_locks + i;
5195 if (match_held_lock(hlock, lock))
5199 for (i--, prev_hlock = hlock--;
5201 i--, prev_hlock = hlock--) {
5203 * We must not cross into another context:
5205 if (prev_hlock->irq_context != hlock->irq_context) {
5209 if (match_held_lock(hlock, lock)) {
5220 static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
5221 int idx, unsigned int *merged)
5223 struct held_lock *hlock;
5224 int first_idx = idx;
5226 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
5229 for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
5230 switch (__lock_acquire(hlock->instance,
5231 hlock_class(hlock)->subclass,
5233 hlock->read, hlock->check,
5234 hlock->hardirqs_off,
5235 hlock->nest_lock, hlock->acquire_ip,
5236 hlock->references, hlock->pin_count, 0)) {
5242 *merged += (idx == first_idx);
5253 __lock_set_class(struct lockdep_map *lock, const char *name,
5254 struct lock_class_key *key, unsigned int subclass,
5257 struct task_struct *curr = current;
5258 unsigned int depth, merged = 0;
5259 struct held_lock *hlock;
5260 struct lock_class *class;
5263 if (unlikely(!debug_locks))
5266 depth = curr->lockdep_depth;
5268 * This function is about (re)setting the class of a held lock,
5269 * yet we're not actually holding any locks. Naughty user!
5271 if (DEBUG_LOCKS_WARN_ON(!depth))
5274 hlock = find_held_lock(curr, lock, depth, &i);
5276 print_unlock_imbalance_bug(curr, lock, ip);
5280 lockdep_init_map_type(lock, name, key, 0,
5281 lock->wait_type_inner,
5282 lock->wait_type_outer,
5284 class = register_lock_class(lock, subclass, 0);
5285 hlock->class_idx = class - lock_classes;
5287 curr->lockdep_depth = i;
5288 curr->curr_chain_key = hlock->prev_chain_key;
5290 if (reacquire_held_locks(curr, depth, i, &merged))
5294 * I took it apart and put it back together again, except now I have
5295 * these 'spare' parts.. where shall I put them.
5297 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged))
5302 static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5304 struct task_struct *curr = current;
5305 unsigned int depth, merged = 0;
5306 struct held_lock *hlock;
5309 if (unlikely(!debug_locks))
5312 depth = curr->lockdep_depth;
5314 * This function is about (re)setting the class of a held lock,
5315 * yet we're not actually holding any locks. Naughty user!
5317 if (DEBUG_LOCKS_WARN_ON(!depth))
5320 hlock = find_held_lock(curr, lock, depth, &i);
5322 print_unlock_imbalance_bug(curr, lock, ip);
5326 curr->lockdep_depth = i;
5327 curr->curr_chain_key = hlock->prev_chain_key;
5329 WARN(hlock->read, "downgrading a read lock");
5331 hlock->acquire_ip = ip;
5333 if (reacquire_held_locks(curr, depth, i, &merged))
5336 /* Merging can't happen with unchanged classes.. */
5337 if (DEBUG_LOCKS_WARN_ON(merged))
5341 * I took it apart and put it back together again, except now I have
5342 * these 'spare' parts.. where shall I put them.
5344 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
5351 * Remove the lock from the list of currently held locks - this gets
5352 * called on mutex_unlock()/spin_unlock*() (or on a failed
5353 * mutex_lock_interruptible()).
5356 __lock_release(struct lockdep_map *lock, unsigned long ip)
5358 struct task_struct *curr = current;
5359 unsigned int depth, merged = 1;
5360 struct held_lock *hlock;
5363 if (unlikely(!debug_locks))
5366 depth = curr->lockdep_depth;
5368 * So we're all set to release this lock.. wait what lock? We don't
5369 * own any locks, you've been drinking again?
5372 print_unlock_imbalance_bug(curr, lock, ip);
5377 * Check whether the lock exists in the current stack
5380 hlock = find_held_lock(curr, lock, depth, &i);
5382 print_unlock_imbalance_bug(curr, lock, ip);
5386 if (hlock->instance == lock)
5387 lock_release_holdtime(hlock);
5389 WARN(hlock->pin_count, "releasing a pinned lock\n");
5391 if (hlock->references) {
5392 hlock->references--;
5393 if (hlock->references) {
5395 * We had, and after removing one, still have
5396 * references, the current lock stack is still
5397 * valid. We're done!
5404 * We have the right lock to unlock, 'hlock' points to it.
5405 * Now we remove it from the stack, and add back the other
5406 * entries (if any), recalculating the hash along the way:
5409 curr->lockdep_depth = i;
5410 curr->curr_chain_key = hlock->prev_chain_key;
5413 * The most likely case is when the unlock is on the innermost
5414 * lock. In this case, we are done!
5419 if (reacquire_held_locks(curr, depth, i + 1, &merged))
5423 * We had N bottles of beer on the wall, we drank one, but now
5424 * there's not N-1 bottles of beer left on the wall...
5425 * Pouring two of the bottles together is acceptable.
5427 DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
5430 * Since reacquire_held_locks() would have called check_chain_key()
5431 * indirectly via __lock_acquire(), we don't need to do it again
5437 static __always_inline
5438 int __lock_is_held(const struct lockdep_map *lock, int read)
5440 struct task_struct *curr = current;
5443 for (i = 0; i < curr->lockdep_depth; i++) {
5444 struct held_lock *hlock = curr->held_locks + i;
5446 if (match_held_lock(hlock, lock)) {
5447 if (read == -1 || !!hlock->read == read)
5448 return LOCK_STATE_HELD;
5450 return LOCK_STATE_NOT_HELD;
5454 return LOCK_STATE_NOT_HELD;
5457 static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
5459 struct pin_cookie cookie = NIL_COOKIE;
5460 struct task_struct *curr = current;
5463 if (unlikely(!debug_locks))
5466 for (i = 0; i < curr->lockdep_depth; i++) {
5467 struct held_lock *hlock = curr->held_locks + i;
5469 if (match_held_lock(hlock, lock)) {
5471 * Grab 16bits of randomness; this is sufficient to not
5472 * be guessable and still allows some pin nesting in
5473 * our u32 pin_count.
5475 cookie.val = 1 + (sched_clock() & 0xffff);
5476 hlock->pin_count += cookie.val;
5481 WARN(1, "pinning an unheld lock\n");
5485 static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5487 struct task_struct *curr = current;
5490 if (unlikely(!debug_locks))
5493 for (i = 0; i < curr->lockdep_depth; i++) {
5494 struct held_lock *hlock = curr->held_locks + i;
5496 if (match_held_lock(hlock, lock)) {
5497 hlock->pin_count += cookie.val;
5502 WARN(1, "pinning an unheld lock\n");
5505 static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5507 struct task_struct *curr = current;
5510 if (unlikely(!debug_locks))
5513 for (i = 0; i < curr->lockdep_depth; i++) {
5514 struct held_lock *hlock = curr->held_locks + i;
5516 if (match_held_lock(hlock, lock)) {
5517 if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
5520 hlock->pin_count -= cookie.val;
5522 if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
5523 hlock->pin_count = 0;
5529 WARN(1, "unpinning an unheld lock\n");
5533 * Check whether we follow the irq-flags state precisely:
5535 static noinstr void check_flags(unsigned long flags)
5537 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP)
5541 /* Get the warning out.. */
5542 instrumentation_begin();
5544 if (irqs_disabled_flags(flags)) {
5545 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())) {
5546 printk("possible reason: unannotated irqs-off.\n");
5549 if (DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())) {
5550 printk("possible reason: unannotated irqs-on.\n");
5554 #ifndef CONFIG_PREEMPT_RT
5556 * We dont accurately track softirq state in e.g.
5557 * hardirq contexts (such as on 4KSTACKS), so only
5558 * check if not in hardirq contexts:
5560 if (!hardirq_count()) {
5561 if (softirq_count()) {
5562 /* like the above, but with softirqs */
5563 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
5565 /* lick the above, does it taste good? */
5566 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
5572 print_irqtrace_events(current);
5574 instrumentation_end();
5578 void lock_set_class(struct lockdep_map *lock, const char *name,
5579 struct lock_class_key *key, unsigned int subclass,
5582 unsigned long flags;
5584 if (unlikely(!lockdep_enabled()))
5587 raw_local_irq_save(flags);
5588 lockdep_recursion_inc();
5590 if (__lock_set_class(lock, name, key, subclass, ip))
5591 check_chain_key(current);
5592 lockdep_recursion_finish();
5593 raw_local_irq_restore(flags);
5595 EXPORT_SYMBOL_GPL(lock_set_class);
5597 void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5599 unsigned long flags;
5601 if (unlikely(!lockdep_enabled()))
5604 raw_local_irq_save(flags);
5605 lockdep_recursion_inc();
5607 if (__lock_downgrade(lock, ip))
5608 check_chain_key(current);
5609 lockdep_recursion_finish();
5610 raw_local_irq_restore(flags);
5612 EXPORT_SYMBOL_GPL(lock_downgrade);
5614 /* NMI context !!! */
5615 static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock, int subclass)
5617 #ifdef CONFIG_PROVE_LOCKING
5618 struct lock_class *class = look_up_lock_class(lock, subclass);
5619 unsigned long mask = LOCKF_USED;
5621 /* if it doesn't have a class (yet), it certainly hasn't been used yet */
5626 * READ locks only conflict with USED, such that if we only ever use
5627 * READ locks, there is no deadlock possible -- RCU.
5630 mask |= LOCKF_USED_READ;
5632 if (!(class->usage_mask & mask))
5635 hlock->class_idx = class - lock_classes;
5637 print_usage_bug(current, hlock, LOCK_USED, LOCK_USAGE_STATES);
5641 static bool lockdep_nmi(void)
5643 if (raw_cpu_read(lockdep_recursion))
5653 * read_lock() is recursive if:
5654 * 1. We force lockdep think this way in selftests or
5655 * 2. The implementation is not queued read/write lock or
5656 * 3. The locker is at an in_interrupt() context.
5658 bool read_lock_is_recursive(void)
5660 return force_read_lock_recursive ||
5661 !IS_ENABLED(CONFIG_QUEUED_RWLOCKS) ||
5664 EXPORT_SYMBOL_GPL(read_lock_is_recursive);
5667 * We are not always called with irqs disabled - do that here,
5668 * and also avoid lockdep recursion:
5670 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
5671 int trylock, int read, int check,
5672 struct lockdep_map *nest_lock, unsigned long ip)
5674 unsigned long flags;
5676 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
5681 if (unlikely(!lockdep_enabled())) {
5682 /* XXX allow trylock from NMI ?!? */
5683 if (lockdep_nmi() && !trylock) {
5684 struct held_lock hlock;
5686 hlock.acquire_ip = ip;
5687 hlock.instance = lock;
5688 hlock.nest_lock = nest_lock;
5689 hlock.irq_context = 2; // XXX
5690 hlock.trylock = trylock;
5692 hlock.check = check;
5693 hlock.hardirqs_off = true;
5694 hlock.references = 0;
5696 verify_lock_unused(lock, &hlock, subclass);
5701 raw_local_irq_save(flags);
5704 lockdep_recursion_inc();
5705 __lock_acquire(lock, subclass, trylock, read, check,
5706 irqs_disabled_flags(flags), nest_lock, ip, 0, 0, 0);
5707 lockdep_recursion_finish();
5708 raw_local_irq_restore(flags);
5710 EXPORT_SYMBOL_GPL(lock_acquire);
5712 void lock_release(struct lockdep_map *lock, unsigned long ip)
5714 unsigned long flags;
5716 trace_lock_release(lock, ip);
5718 if (unlikely(!lockdep_enabled()))
5721 raw_local_irq_save(flags);
5724 lockdep_recursion_inc();
5725 if (__lock_release(lock, ip))
5726 check_chain_key(current);
5727 lockdep_recursion_finish();
5728 raw_local_irq_restore(flags);
5730 EXPORT_SYMBOL_GPL(lock_release);
5733 * lock_sync() - A special annotation for synchronize_{s,}rcu()-like API.
5735 * No actual critical section is created by the APIs annotated with this: these
5736 * APIs are used to wait for one or multiple critical sections (on other CPUs
5737 * or threads), and it means that calling these APIs inside these critical
5738 * sections is potential deadlock.
5740 void lock_sync(struct lockdep_map *lock, unsigned subclass, int read,
5741 int check, struct lockdep_map *nest_lock, unsigned long ip)
5743 unsigned long flags;
5745 if (unlikely(!lockdep_enabled()))
5748 raw_local_irq_save(flags);
5751 lockdep_recursion_inc();
5752 __lock_acquire(lock, subclass, 0, read, check,
5753 irqs_disabled_flags(flags), nest_lock, ip, 0, 0, 1);
5754 check_chain_key(current);
5755 lockdep_recursion_finish();
5756 raw_local_irq_restore(flags);
5758 EXPORT_SYMBOL_GPL(lock_sync);
5760 noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
5762 unsigned long flags;
5763 int ret = LOCK_STATE_NOT_HELD;
5766 * Avoid false negative lockdep_assert_held() and
5767 * lockdep_assert_not_held().
5769 if (unlikely(!lockdep_enabled()))
5770 return LOCK_STATE_UNKNOWN;
5772 raw_local_irq_save(flags);
5775 lockdep_recursion_inc();
5776 ret = __lock_is_held(lock, read);
5777 lockdep_recursion_finish();
5778 raw_local_irq_restore(flags);
5782 EXPORT_SYMBOL_GPL(lock_is_held_type);
5783 NOKPROBE_SYMBOL(lock_is_held_type);
5785 struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
5787 struct pin_cookie cookie = NIL_COOKIE;
5788 unsigned long flags;
5790 if (unlikely(!lockdep_enabled()))
5793 raw_local_irq_save(flags);
5796 lockdep_recursion_inc();
5797 cookie = __lock_pin_lock(lock);
5798 lockdep_recursion_finish();
5799 raw_local_irq_restore(flags);
5803 EXPORT_SYMBOL_GPL(lock_pin_lock);
5805 void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5807 unsigned long flags;
5809 if (unlikely(!lockdep_enabled()))
5812 raw_local_irq_save(flags);
5815 lockdep_recursion_inc();
5816 __lock_repin_lock(lock, cookie);
5817 lockdep_recursion_finish();
5818 raw_local_irq_restore(flags);
5820 EXPORT_SYMBOL_GPL(lock_repin_lock);
5822 void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5824 unsigned long flags;
5826 if (unlikely(!lockdep_enabled()))
5829 raw_local_irq_save(flags);
5832 lockdep_recursion_inc();
5833 __lock_unpin_lock(lock, cookie);
5834 lockdep_recursion_finish();
5835 raw_local_irq_restore(flags);
5837 EXPORT_SYMBOL_GPL(lock_unpin_lock);
5839 #ifdef CONFIG_LOCK_STAT
5840 static void print_lock_contention_bug(struct task_struct *curr,
5841 struct lockdep_map *lock,
5844 if (!debug_locks_off())
5846 if (debug_locks_silent)
5850 pr_warn("=================================\n");
5851 pr_warn("WARNING: bad contention detected!\n");
5852 print_kernel_ident();
5853 pr_warn("---------------------------------\n");
5854 pr_warn("%s/%d is trying to contend lock (",
5855 curr->comm, task_pid_nr(curr));
5856 print_lockdep_cache(lock);
5858 print_ip_sym(KERN_WARNING, ip);
5859 pr_warn("but there are no locks held!\n");
5860 pr_warn("\nother info that might help us debug this:\n");
5861 lockdep_print_held_locks(curr);
5863 pr_warn("\nstack backtrace:\n");
5868 __lock_contended(struct lockdep_map *lock, unsigned long ip)
5870 struct task_struct *curr = current;
5871 struct held_lock *hlock;
5872 struct lock_class_stats *stats;
5874 int i, contention_point, contending_point;
5876 depth = curr->lockdep_depth;
5878 * Whee, we contended on this lock, except it seems we're not
5879 * actually trying to acquire anything much at all..
5881 if (DEBUG_LOCKS_WARN_ON(!depth))
5884 hlock = find_held_lock(curr, lock, depth, &i);
5886 print_lock_contention_bug(curr, lock, ip);
5890 if (hlock->instance != lock)
5893 hlock->waittime_stamp = lockstat_clock();
5895 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
5896 contending_point = lock_point(hlock_class(hlock)->contending_point,
5899 stats = get_lock_stats(hlock_class(hlock));
5900 if (contention_point < LOCKSTAT_POINTS)
5901 stats->contention_point[contention_point]++;
5902 if (contending_point < LOCKSTAT_POINTS)
5903 stats->contending_point[contending_point]++;
5904 if (lock->cpu != smp_processor_id())
5905 stats->bounces[bounce_contended + !!hlock->read]++;
5909 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
5911 struct task_struct *curr = current;
5912 struct held_lock *hlock;
5913 struct lock_class_stats *stats;
5915 u64 now, waittime = 0;
5918 depth = curr->lockdep_depth;
5920 * Yay, we acquired ownership of this lock we didn't try to
5921 * acquire, how the heck did that happen?
5923 if (DEBUG_LOCKS_WARN_ON(!depth))
5926 hlock = find_held_lock(curr, lock, depth, &i);
5928 print_lock_contention_bug(curr, lock, _RET_IP_);
5932 if (hlock->instance != lock)
5935 cpu = smp_processor_id();
5936 if (hlock->waittime_stamp) {
5937 now = lockstat_clock();
5938 waittime = now - hlock->waittime_stamp;
5939 hlock->holdtime_stamp = now;
5942 stats = get_lock_stats(hlock_class(hlock));
5945 lock_time_inc(&stats->read_waittime, waittime);
5947 lock_time_inc(&stats->write_waittime, waittime);
5949 if (lock->cpu != cpu)
5950 stats->bounces[bounce_acquired + !!hlock->read]++;
5956 void lock_contended(struct lockdep_map *lock, unsigned long ip)
5958 unsigned long flags;
5960 trace_lock_contended(lock, ip);
5962 if (unlikely(!lock_stat || !lockdep_enabled()))
5965 raw_local_irq_save(flags);
5967 lockdep_recursion_inc();
5968 __lock_contended(lock, ip);
5969 lockdep_recursion_finish();
5970 raw_local_irq_restore(flags);
5972 EXPORT_SYMBOL_GPL(lock_contended);
5974 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
5976 unsigned long flags;
5978 trace_lock_acquired(lock, ip);
5980 if (unlikely(!lock_stat || !lockdep_enabled()))
5983 raw_local_irq_save(flags);
5985 lockdep_recursion_inc();
5986 __lock_acquired(lock, ip);
5987 lockdep_recursion_finish();
5988 raw_local_irq_restore(flags);
5990 EXPORT_SYMBOL_GPL(lock_acquired);
5994 * Used by the testsuite, sanitize the validator state
5995 * after a simulated failure:
5998 void lockdep_reset(void)
6000 unsigned long flags;
6003 raw_local_irq_save(flags);
6004 lockdep_init_task(current);
6005 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
6006 nr_hardirq_chains = 0;
6007 nr_softirq_chains = 0;
6008 nr_process_chains = 0;
6010 for (i = 0; i < CHAINHASH_SIZE; i++)
6011 INIT_HLIST_HEAD(chainhash_table + i);
6012 raw_local_irq_restore(flags);
6015 /* Remove a class from a lock chain. Must be called with the graph lock held. */
6016 static void remove_class_from_lock_chain(struct pending_free *pf,
6017 struct lock_chain *chain,
6018 struct lock_class *class)
6020 #ifdef CONFIG_PROVE_LOCKING
6023 for (i = chain->base; i < chain->base + chain->depth; i++) {
6024 if (chain_hlock_class_idx(chain_hlocks[i]) != class - lock_classes)
6027 * Each lock class occurs at most once in a lock chain so once
6028 * we found a match we can break out of this loop.
6030 goto free_lock_chain;
6032 /* Since the chain has not been modified, return. */
6036 free_chain_hlocks(chain->base, chain->depth);
6037 /* Overwrite the chain key for concurrent RCU readers. */
6038 WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY);
6039 dec_chains(chain->irq_context);
6042 * Note: calling hlist_del_rcu() from inside a
6043 * hlist_for_each_entry_rcu() loop is safe.
6045 hlist_del_rcu(&chain->entry);
6046 __set_bit(chain - lock_chains, pf->lock_chains_being_freed);
6047 nr_zapped_lock_chains++;
6051 /* Must be called with the graph lock held. */
6052 static void remove_class_from_lock_chains(struct pending_free *pf,
6053 struct lock_class *class)
6055 struct lock_chain *chain;
6056 struct hlist_head *head;
6059 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
6060 head = chainhash_table + i;
6061 hlist_for_each_entry_rcu(chain, head, entry) {
6062 remove_class_from_lock_chain(pf, chain, class);
6068 * Remove all references to a lock class. The caller must hold the graph lock.
6070 static void zap_class(struct pending_free *pf, struct lock_class *class)
6072 struct lock_list *entry;
6075 WARN_ON_ONCE(!class->key);
6078 * Remove all dependencies this lock is
6081 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
6082 entry = list_entries + i;
6083 if (entry->class != class && entry->links_to != class)
6085 __clear_bit(i, list_entries_in_use);
6087 list_del_rcu(&entry->entry);
6089 if (list_empty(&class->locks_after) &&
6090 list_empty(&class->locks_before)) {
6091 list_move_tail(&class->lock_entry, &pf->zapped);
6092 hlist_del_rcu(&class->hash_entry);
6093 WRITE_ONCE(class->key, NULL);
6094 WRITE_ONCE(class->name, NULL);
6096 __clear_bit(class - lock_classes, lock_classes_in_use);
6097 if (class - lock_classes == max_lock_class_idx)
6098 max_lock_class_idx--;
6100 WARN_ONCE(true, "%s() failed for class %s\n", __func__,
6104 remove_class_from_lock_chains(pf, class);
6105 nr_zapped_classes++;
6108 static void reinit_class(struct lock_class *class)
6110 WARN_ON_ONCE(!class->lock_entry.next);
6111 WARN_ON_ONCE(!list_empty(&class->locks_after));
6112 WARN_ON_ONCE(!list_empty(&class->locks_before));
6113 memset_startat(class, 0, key);
6114 WARN_ON_ONCE(!class->lock_entry.next);
6115 WARN_ON_ONCE(!list_empty(&class->locks_after));
6116 WARN_ON_ONCE(!list_empty(&class->locks_before));
6119 static inline int within(const void *addr, void *start, unsigned long size)
6121 return addr >= start && addr < start + size;
6124 static bool inside_selftest(void)
6126 return current == lockdep_selftest_task_struct;
6129 /* The caller must hold the graph lock. */
6130 static struct pending_free *get_pending_free(void)
6132 return delayed_free.pf + delayed_free.index;
6135 static void free_zapped_rcu(struct rcu_head *cb);
6138 * Schedule an RCU callback if no RCU callback is pending. Must be called with
6139 * the graph lock held.
6141 static void call_rcu_zapped(struct pending_free *pf)
6143 WARN_ON_ONCE(inside_selftest());
6145 if (list_empty(&pf->zapped))
6148 if (delayed_free.scheduled)
6151 delayed_free.scheduled = true;
6153 WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
6154 delayed_free.index ^= 1;
6156 call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
6159 /* The caller must hold the graph lock. May be called from RCU context. */
6160 static void __free_zapped_classes(struct pending_free *pf)
6162 struct lock_class *class;
6164 check_data_structures();
6166 list_for_each_entry(class, &pf->zapped, lock_entry)
6167 reinit_class(class);
6169 list_splice_init(&pf->zapped, &free_lock_classes);
6171 #ifdef CONFIG_PROVE_LOCKING
6172 bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
6173 pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
6174 bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
6178 static void free_zapped_rcu(struct rcu_head *ch)
6180 struct pending_free *pf;
6181 unsigned long flags;
6183 if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
6186 raw_local_irq_save(flags);
6190 pf = delayed_free.pf + (delayed_free.index ^ 1);
6191 __free_zapped_classes(pf);
6192 delayed_free.scheduled = false;
6195 * If there's anything on the open list, close and start a new callback.
6197 call_rcu_zapped(delayed_free.pf + delayed_free.index);
6200 raw_local_irq_restore(flags);
6204 * Remove all lock classes from the class hash table and from the
6205 * all_lock_classes list whose key or name is in the address range [start,
6206 * start + size). Move these lock classes to the zapped_classes list. Must
6207 * be called with the graph lock held.
6209 static void __lockdep_free_key_range(struct pending_free *pf, void *start,
6212 struct lock_class *class;
6213 struct hlist_head *head;
6216 /* Unhash all classes that were created by a module. */
6217 for (i = 0; i < CLASSHASH_SIZE; i++) {
6218 head = classhash_table + i;
6219 hlist_for_each_entry_rcu(class, head, hash_entry) {
6220 if (!within(class->key, start, size) &&
6221 !within(class->name, start, size))
6223 zap_class(pf, class);
6229 * Used in module.c to remove lock classes from memory that is going to be
6230 * freed; and possibly re-used by other modules.
6232 * We will have had one synchronize_rcu() before getting here, so we're
6233 * guaranteed nobody will look up these exact classes -- they're properly dead
6234 * but still allocated.
6236 static void lockdep_free_key_range_reg(void *start, unsigned long size)
6238 struct pending_free *pf;
6239 unsigned long flags;
6241 init_data_structures_once();
6243 raw_local_irq_save(flags);
6245 pf = get_pending_free();
6246 __lockdep_free_key_range(pf, start, size);
6247 call_rcu_zapped(pf);
6249 raw_local_irq_restore(flags);
6252 * Wait for any possible iterators from look_up_lock_class() to pass
6253 * before continuing to free the memory they refer to.
6259 * Free all lockdep keys in the range [start, start+size). Does not sleep.
6260 * Ignores debug_locks. Must only be used by the lockdep selftests.
6262 static void lockdep_free_key_range_imm(void *start, unsigned long size)
6264 struct pending_free *pf = delayed_free.pf;
6265 unsigned long flags;
6267 init_data_structures_once();
6269 raw_local_irq_save(flags);
6271 __lockdep_free_key_range(pf, start, size);
6272 __free_zapped_classes(pf);
6274 raw_local_irq_restore(flags);
6277 void lockdep_free_key_range(void *start, unsigned long size)
6279 init_data_structures_once();
6281 if (inside_selftest())
6282 lockdep_free_key_range_imm(start, size);
6284 lockdep_free_key_range_reg(start, size);
6288 * Check whether any element of the @lock->class_cache[] array refers to a
6289 * registered lock class. The caller must hold either the graph lock or the
6292 static bool lock_class_cache_is_registered(struct lockdep_map *lock)
6294 struct lock_class *class;
6295 struct hlist_head *head;
6298 for (i = 0; i < CLASSHASH_SIZE; i++) {
6299 head = classhash_table + i;
6300 hlist_for_each_entry_rcu(class, head, hash_entry) {
6301 for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
6302 if (lock->class_cache[j] == class)
6309 /* The caller must hold the graph lock. Does not sleep. */
6310 static void __lockdep_reset_lock(struct pending_free *pf,
6311 struct lockdep_map *lock)
6313 struct lock_class *class;
6317 * Remove all classes this lock might have:
6319 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
6321 * If the class exists we look it up and zap it:
6323 class = look_up_lock_class(lock, j);
6325 zap_class(pf, class);
6328 * Debug check: in the end all mapped classes should
6331 if (WARN_ON_ONCE(lock_class_cache_is_registered(lock)))
6336 * Remove all information lockdep has about a lock if debug_locks == 1. Free
6337 * released data structures from RCU context.
6339 static void lockdep_reset_lock_reg(struct lockdep_map *lock)
6341 struct pending_free *pf;
6342 unsigned long flags;
6345 raw_local_irq_save(flags);
6346 locked = graph_lock();
6350 pf = get_pending_free();
6351 __lockdep_reset_lock(pf, lock);
6352 call_rcu_zapped(pf);
6356 raw_local_irq_restore(flags);
6360 * Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the
6361 * lockdep selftests.
6363 static void lockdep_reset_lock_imm(struct lockdep_map *lock)
6365 struct pending_free *pf = delayed_free.pf;
6366 unsigned long flags;
6368 raw_local_irq_save(flags);
6370 __lockdep_reset_lock(pf, lock);
6371 __free_zapped_classes(pf);
6373 raw_local_irq_restore(flags);
6376 void lockdep_reset_lock(struct lockdep_map *lock)
6378 init_data_structures_once();
6380 if (inside_selftest())
6381 lockdep_reset_lock_imm(lock);
6383 lockdep_reset_lock_reg(lock);
6387 * Unregister a dynamically allocated key.
6389 * Unlike lockdep_register_key(), a search is always done to find a matching
6390 * key irrespective of debug_locks to avoid potential invalid access to freed
6391 * memory in lock_class entry.
6393 void lockdep_unregister_key(struct lock_class_key *key)
6395 struct hlist_head *hash_head = keyhashentry(key);
6396 struct lock_class_key *k;
6397 struct pending_free *pf;
6398 unsigned long flags;
6403 if (WARN_ON_ONCE(static_obj(key)))
6406 raw_local_irq_save(flags);
6409 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
6411 hlist_del_rcu(&k->hash_entry);
6416 WARN_ON_ONCE(!found && debug_locks);
6418 pf = get_pending_free();
6419 __lockdep_free_key_range(pf, key, 1);
6420 call_rcu_zapped(pf);
6423 raw_local_irq_restore(flags);
6425 /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
6428 EXPORT_SYMBOL_GPL(lockdep_unregister_key);
6430 void __init lockdep_init(void)
6432 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
6434 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
6435 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
6436 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
6437 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
6438 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
6439 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
6440 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
6442 printk(" memory used by lock dependency info: %zu kB\n",
6443 (sizeof(lock_classes) +
6444 sizeof(lock_classes_in_use) +
6445 sizeof(classhash_table) +
6446 sizeof(list_entries) +
6447 sizeof(list_entries_in_use) +
6448 sizeof(chainhash_table) +
6449 sizeof(delayed_free)
6450 #ifdef CONFIG_PROVE_LOCKING
6452 + sizeof(lock_chains)
6453 + sizeof(lock_chains_in_use)
6454 + sizeof(chain_hlocks)
6459 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
6460 printk(" memory used for stack traces: %zu kB\n",
6461 (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024
6465 printk(" per task-struct memory footprint: %zu bytes\n",
6466 sizeof(((struct task_struct *)NULL)->held_locks));
6470 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
6471 const void *mem_to, struct held_lock *hlock)
6473 if (!debug_locks_off())
6475 if (debug_locks_silent)
6479 pr_warn("=========================\n");
6480 pr_warn("WARNING: held lock freed!\n");
6481 print_kernel_ident();
6482 pr_warn("-------------------------\n");
6483 pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n",
6484 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
6486 lockdep_print_held_locks(curr);
6488 pr_warn("\nstack backtrace:\n");
6492 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
6493 const void* lock_from, unsigned long lock_len)
6495 return lock_from + lock_len <= mem_from ||
6496 mem_from + mem_len <= lock_from;
6500 * Called when kernel memory is freed (or unmapped), or if a lock
6501 * is destroyed or reinitialized - this code checks whether there is
6502 * any held lock in the memory range of <from> to <to>:
6504 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
6506 struct task_struct *curr = current;
6507 struct held_lock *hlock;
6508 unsigned long flags;
6511 if (unlikely(!debug_locks))
6514 raw_local_irq_save(flags);
6515 for (i = 0; i < curr->lockdep_depth; i++) {
6516 hlock = curr->held_locks + i;
6518 if (not_in_range(mem_from, mem_len, hlock->instance,
6519 sizeof(*hlock->instance)))
6522 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
6525 raw_local_irq_restore(flags);
6527 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
6529 static void print_held_locks_bug(void)
6531 if (!debug_locks_off())
6533 if (debug_locks_silent)
6537 pr_warn("====================================\n");
6538 pr_warn("WARNING: %s/%d still has locks held!\n",
6539 current->comm, task_pid_nr(current));
6540 print_kernel_ident();
6541 pr_warn("------------------------------------\n");
6542 lockdep_print_held_locks(current);
6543 pr_warn("\nstack backtrace:\n");
6547 void debug_check_no_locks_held(void)
6549 if (unlikely(current->lockdep_depth > 0))
6550 print_held_locks_bug();
6552 EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
6555 void debug_show_all_locks(void)
6557 struct task_struct *g, *p;
6559 if (unlikely(!debug_locks)) {
6560 pr_warn("INFO: lockdep is turned off.\n");
6563 pr_warn("\nShowing all locks held in the system:\n");
6566 for_each_process_thread(g, p) {
6567 if (!p->lockdep_depth)
6569 lockdep_print_held_locks(p);
6570 touch_nmi_watchdog();
6571 touch_all_softlockup_watchdogs();
6576 pr_warn("=============================================\n\n");
6578 EXPORT_SYMBOL_GPL(debug_show_all_locks);
6582 * Careful: only use this function if you are sure that
6583 * the task cannot run in parallel!
6585 void debug_show_held_locks(struct task_struct *task)
6587 if (unlikely(!debug_locks)) {
6588 printk("INFO: lockdep is turned off.\n");
6591 lockdep_print_held_locks(task);
6593 EXPORT_SYMBOL_GPL(debug_show_held_locks);
6595 asmlinkage __visible void lockdep_sys_exit(void)
6597 struct task_struct *curr = current;
6599 if (unlikely(curr->lockdep_depth)) {
6600 if (!debug_locks_off())
6603 pr_warn("================================================\n");
6604 pr_warn("WARNING: lock held when returning to user space!\n");
6605 print_kernel_ident();
6606 pr_warn("------------------------------------------------\n");
6607 pr_warn("%s/%d is leaving the kernel with locks still held!\n",
6608 curr->comm, curr->pid);
6609 lockdep_print_held_locks(curr);
6613 * The lock history for each syscall should be independent. So wipe the
6614 * slate clean on return to userspace.
6616 lockdep_invariant_state(false);
6619 void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
6621 struct task_struct *curr = current;
6622 int dl = READ_ONCE(debug_locks);
6623 bool rcu = warn_rcu_enter();
6625 /* Note: the following can be executed concurrently, so be careful. */
6627 pr_warn("=============================\n");
6628 pr_warn("WARNING: suspicious RCU usage\n");
6629 print_kernel_ident();
6630 pr_warn("-----------------------------\n");
6631 pr_warn("%s:%d %s!\n", file, line, s);
6632 pr_warn("\nother info that might help us debug this:\n\n");
6633 pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n%s",
6634 !rcu_lockdep_current_cpu_online()
6635 ? "RCU used illegally from offline CPU!\n"
6637 rcu_scheduler_active, dl,
6638 dl ? "" : "Possible false positive due to lockdep disabling via debug_locks = 0\n");
6641 * If a CPU is in the RCU-free window in idle (ie: in the section
6642 * between ct_idle_enter() and ct_idle_exit(), then RCU
6643 * considers that CPU to be in an "extended quiescent state",
6644 * which means that RCU will be completely ignoring that CPU.
6645 * Therefore, rcu_read_lock() and friends have absolutely no
6646 * effect on a CPU running in that state. In other words, even if
6647 * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
6648 * delete data structures out from under it. RCU really has no
6649 * choice here: we need to keep an RCU-free window in idle where
6650 * the CPU may possibly enter into low power mode. This way we can
6651 * notice an extended quiescent state to other CPUs that started a grace
6652 * period. Otherwise we would delay any grace period as long as we run
6655 * So complain bitterly if someone does call rcu_read_lock(),
6656 * rcu_read_lock_bh() and so on from extended quiescent states.
6658 if (!rcu_is_watching())
6659 pr_warn("RCU used illegally from extended quiescent state!\n");
6661 lockdep_print_held_locks(curr);
6662 pr_warn("\nstack backtrace:\n");
6666 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);