4 * Runtime locking correctness validator
6 * Started by Ingo Molnar:
8 * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
9 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
11 * this code maps all the lock dependencies as they occur in a live kernel
12 * and will warn about the following classes of locking bugs:
14 * - lock inversion scenarios
15 * - circular lock dependencies
16 * - hardirq/softirq safe/unsafe locking bugs
18 * Bugs are reported even if the current locking scenario does not cause
19 * any deadlock at this point.
21 * I.e. if anytime in the past two locks were taken in a different order,
22 * even if it happened for another task, even if those were different
23 * locks (but of the same class as this lock), this code will detect it.
25 * Thanks to Arjan van de Ven for coming up with the initial idea of
26 * mapping lock dependencies runtime.
28 #define DISABLE_BRANCH_PROFILING
29 #include <linux/mutex.h>
30 #include <linux/sched.h>
31 #include <linux/sched/clock.h>
32 #include <linux/sched/task.h>
33 #include <linux/sched/mm.h>
34 #include <linux/delay.h>
35 #include <linux/module.h>
36 #include <linux/proc_fs.h>
37 #include <linux/seq_file.h>
38 #include <linux/spinlock.h>
39 #include <linux/kallsyms.h>
40 #include <linux/interrupt.h>
41 #include <linux/stacktrace.h>
42 #include <linux/debug_locks.h>
43 #include <linux/irqflags.h>
44 #include <linux/utsname.h>
45 #include <linux/hash.h>
46 #include <linux/ftrace.h>
47 #include <linux/stringify.h>
48 #include <linux/bitops.h>
49 #include <linux/gfp.h>
50 #include <linux/random.h>
51 #include <linux/jhash.h>
52 #include <linux/nmi.h>
54 #include <asm/sections.h>
56 #include "lockdep_internals.h"
58 #define CREATE_TRACE_POINTS
59 #include <trace/events/lock.h>
61 #ifdef CONFIG_PROVE_LOCKING
62 int prove_locking = 1;
63 module_param(prove_locking, int, 0644);
65 #define prove_locking 0
68 #ifdef CONFIG_LOCK_STAT
70 module_param(lock_stat, int, 0644);
76 * lockdep_lock: protects the lockdep graph, the hashes and the
77 * class/list/hash allocators.
79 * This is one of the rare exceptions where it's justified
80 * to use a raw spinlock - we really dont want the spinlock
81 * code to recurse back into the lockdep code...
83 static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
85 static int graph_lock(void)
87 arch_spin_lock(&lockdep_lock);
89 * Make sure that if another CPU detected a bug while
90 * walking the graph we dont change it (while the other
91 * CPU is busy printing out stuff with the graph lock
95 arch_spin_unlock(&lockdep_lock);
98 /* prevent any recursions within lockdep from causing deadlocks */
99 current->lockdep_recursion++;
103 static inline int graph_unlock(void)
105 if (debug_locks && !arch_spin_is_locked(&lockdep_lock)) {
107 * The lockdep graph lock isn't locked while we expect it to
108 * be, we're confused now, bye!
110 return DEBUG_LOCKS_WARN_ON(1);
113 current->lockdep_recursion--;
114 arch_spin_unlock(&lockdep_lock);
119 * Turn lock debugging off and return with 0 if it was off already,
120 * and also release the graph lock:
122 static inline int debug_locks_off_graph_unlock(void)
124 int ret = debug_locks_off();
126 arch_spin_unlock(&lockdep_lock);
131 unsigned long nr_list_entries;
132 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
135 * All data structures here are protected by the global debug_lock.
137 * Mutex key structs only get allocated, once during bootup, and never
138 * get freed - this significantly simplifies the debugging code.
140 unsigned long nr_lock_classes;
141 #ifndef CONFIG_DEBUG_LOCKDEP
144 struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
146 static inline struct lock_class *hlock_class(struct held_lock *hlock)
148 if (!hlock->class_idx) {
150 * Someone passed in garbage, we give up.
152 DEBUG_LOCKS_WARN_ON(1);
155 return lock_classes + hlock->class_idx - 1;
158 #ifdef CONFIG_LOCK_STAT
159 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
161 static inline u64 lockstat_clock(void)
163 return local_clock();
166 static int lock_point(unsigned long points[], unsigned long ip)
170 for (i = 0; i < LOCKSTAT_POINTS; i++) {
171 if (points[i] == 0) {
182 static void lock_time_inc(struct lock_time *lt, u64 time)
187 if (time < lt->min || !lt->nr)
194 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
199 if (src->max > dst->max)
202 if (src->min < dst->min || !dst->nr)
205 dst->total += src->total;
209 struct lock_class_stats lock_stats(struct lock_class *class)
211 struct lock_class_stats stats;
214 memset(&stats, 0, sizeof(struct lock_class_stats));
215 for_each_possible_cpu(cpu) {
216 struct lock_class_stats *pcs =
217 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
219 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
220 stats.contention_point[i] += pcs->contention_point[i];
222 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
223 stats.contending_point[i] += pcs->contending_point[i];
225 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
226 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
228 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
229 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
231 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
232 stats.bounces[i] += pcs->bounces[i];
238 void clear_lock_stats(struct lock_class *class)
242 for_each_possible_cpu(cpu) {
243 struct lock_class_stats *cpu_stats =
244 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
246 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
248 memset(class->contention_point, 0, sizeof(class->contention_point));
249 memset(class->contending_point, 0, sizeof(class->contending_point));
252 static struct lock_class_stats *get_lock_stats(struct lock_class *class)
254 return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
257 static void lock_release_holdtime(struct held_lock *hlock)
259 struct lock_class_stats *stats;
265 holdtime = lockstat_clock() - hlock->holdtime_stamp;
267 stats = get_lock_stats(hlock_class(hlock));
269 lock_time_inc(&stats->read_holdtime, holdtime);
271 lock_time_inc(&stats->write_holdtime, holdtime);
274 static inline void lock_release_holdtime(struct held_lock *hlock)
280 * We keep a global list of all lock classes. The list only grows,
281 * never shrinks. The list is only accessed with the lockdep
282 * spinlock lock held.
284 LIST_HEAD(all_lock_classes);
287 * The lockdep classes are in a hash-table as well, for fast lookup:
289 #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
290 #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
291 #define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
292 #define classhashentry(key) (classhash_table + __classhashfn((key)))
294 static struct hlist_head classhash_table[CLASSHASH_SIZE];
297 * We put the lock dependency chains into a hash-table as well, to cache
300 #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
301 #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
302 #define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
303 #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
305 static struct hlist_head chainhash_table[CHAINHASH_SIZE];
308 * The hash key of the lock dependency chains is a hash itself too:
309 * it's a hash of all locks taken up to that lock, including that lock.
310 * It's a 64-bit hash, because it's important for the keys to be
313 static inline u64 iterate_chain_key(u64 key, u32 idx)
315 u32 k0 = key, k1 = key >> 32;
317 __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
319 return k0 | (u64)k1 << 32;
322 void lockdep_off(void)
324 current->lockdep_recursion++;
326 EXPORT_SYMBOL(lockdep_off);
328 void lockdep_on(void)
330 current->lockdep_recursion--;
332 EXPORT_SYMBOL(lockdep_on);
335 * Debugging switches:
339 #define VERY_VERBOSE 0
342 # define HARDIRQ_VERBOSE 1
343 # define SOFTIRQ_VERBOSE 1
345 # define HARDIRQ_VERBOSE 0
346 # define SOFTIRQ_VERBOSE 0
349 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
351 * Quick filtering for interesting events:
353 static int class_filter(struct lock_class *class)
357 if (class->name_version == 1 &&
358 !strcmp(class->name, "lockname"))
360 if (class->name_version == 1 &&
361 !strcmp(class->name, "&struct->lockfield"))
364 /* Filter everything else. 1 would be to allow everything else */
369 static int verbose(struct lock_class *class)
372 return class_filter(class);
378 * Stack-trace: tightly packed array of stack backtrace
379 * addresses. Protected by the graph_lock.
381 unsigned long nr_stack_trace_entries;
382 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
384 static void print_lockdep_off(const char *bug_msg)
386 printk(KERN_DEBUG "%s\n", bug_msg);
387 printk(KERN_DEBUG "turning off the locking correctness validator.\n");
388 #ifdef CONFIG_LOCK_STAT
389 printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
393 static int save_trace(struct stack_trace *trace)
395 trace->nr_entries = 0;
396 trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
397 trace->entries = stack_trace + nr_stack_trace_entries;
401 save_stack_trace(trace);
404 * Some daft arches put -1 at the end to indicate its a full trace.
406 * <rant> this is buggy anyway, since it takes a whole extra entry so a
407 * complete trace that maxes out the entries provided will be reported
408 * as incomplete, friggin useless </rant>
410 if (trace->nr_entries != 0 &&
411 trace->entries[trace->nr_entries-1] == ULONG_MAX)
414 trace->max_entries = trace->nr_entries;
416 nr_stack_trace_entries += trace->nr_entries;
418 if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
419 if (!debug_locks_off_graph_unlock())
422 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
431 unsigned int nr_hardirq_chains;
432 unsigned int nr_softirq_chains;
433 unsigned int nr_process_chains;
434 unsigned int max_lockdep_depth;
436 #ifdef CONFIG_DEBUG_LOCKDEP
438 * Various lockdep statistics:
440 DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
447 #define __USAGE(__STATE) \
448 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
449 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
450 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
451 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
453 static const char *usage_str[] =
455 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
456 #include "lockdep_states.h"
458 [LOCK_USED] = "INITIAL USE",
461 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
463 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
466 static inline unsigned long lock_flag(enum lock_usage_bit bit)
471 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
475 if (class->usage_mask & lock_flag(bit + 2))
477 if (class->usage_mask & lock_flag(bit)) {
479 if (class->usage_mask & lock_flag(bit + 2))
486 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
490 #define LOCKDEP_STATE(__STATE) \
491 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
492 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
493 #include "lockdep_states.h"
499 static void __print_lock_name(struct lock_class *class)
501 char str[KSYM_NAME_LEN];
506 name = __get_key_name(class->key, str);
507 printk(KERN_CONT "%s", name);
509 printk(KERN_CONT "%s", name);
510 if (class->name_version > 1)
511 printk(KERN_CONT "#%d", class->name_version);
513 printk(KERN_CONT "/%d", class->subclass);
517 static void print_lock_name(struct lock_class *class)
519 char usage[LOCK_USAGE_CHARS];
521 get_usage_chars(class, usage);
523 printk(KERN_CONT " (");
524 __print_lock_name(class);
525 printk(KERN_CONT "){%s}", usage);
528 static void print_lockdep_cache(struct lockdep_map *lock)
531 char str[KSYM_NAME_LEN];
535 name = __get_key_name(lock->key->subkeys, str);
537 printk(KERN_CONT "%s", name);
540 static void print_lock(struct held_lock *hlock)
543 * We can be called locklessly through debug_show_all_locks() so be
544 * extra careful, the hlock might have been released and cleared.
546 unsigned int class_idx = hlock->class_idx;
548 /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfields: */
551 if (!class_idx || (class_idx - 1) >= MAX_LOCKDEP_KEYS) {
552 printk(KERN_CONT "<RELEASED>\n");
556 printk(KERN_CONT "%p", hlock->instance);
557 print_lock_name(lock_classes + class_idx - 1);
558 printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
561 static void lockdep_print_held_locks(struct task_struct *p)
563 int i, depth = READ_ONCE(p->lockdep_depth);
566 printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
568 printk("%d lock%s held by %s/%d:\n", depth,
569 depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
571 * It's not reliable to print a task's held locks if it's not sleeping
572 * and it's not the current task.
574 if (p->state == TASK_RUNNING && p != current)
576 for (i = 0; i < depth; i++) {
578 print_lock(p->held_locks + i);
582 static void print_kernel_ident(void)
584 printk("%s %.*s %s\n", init_utsname()->release,
585 (int)strcspn(init_utsname()->version, " "),
586 init_utsname()->version,
590 static int very_verbose(struct lock_class *class)
593 return class_filter(class);
599 * Is this the address of a static object:
602 static int static_obj(void *obj)
604 unsigned long start = (unsigned long) &_stext,
605 end = (unsigned long) &_end,
606 addr = (unsigned long) obj;
611 if ((addr >= start) && (addr < end))
614 if (arch_is_kernel_data(addr))
618 * in-kernel percpu var?
620 if (is_kernel_percpu_address(addr))
624 * module static or percpu var?
626 return is_module_address(addr) || is_module_percpu_address(addr);
631 * To make lock name printouts unique, we calculate a unique
632 * class->name_version generation counter. The caller must hold the graph
635 static int count_matching_names(struct lock_class *new_class)
637 struct lock_class *class;
640 if (!new_class->name)
643 list_for_each_entry(class, &all_lock_classes, lock_entry) {
644 if (new_class->key - new_class->subclass == class->key)
645 return class->name_version;
646 if (class->name && !strcmp(class->name, new_class->name))
647 count = max(count, class->name_version);
653 static inline struct lock_class *
654 look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
656 struct lockdep_subclass_key *key;
657 struct hlist_head *hash_head;
658 struct lock_class *class;
660 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
663 "BUG: looking up invalid subclass: %u\n", subclass);
665 "turning off the locking correctness validator.\n");
671 * If it is not initialised then it has never been locked,
672 * so it won't be present in the hash table.
674 if (unlikely(!lock->key))
678 * NOTE: the class-key must be unique. For dynamic locks, a static
679 * lock_class_key variable is passed in through the mutex_init()
680 * (or spin_lock_init()) call - which acts as the key. For static
681 * locks we use the lock object itself as the key.
683 BUILD_BUG_ON(sizeof(struct lock_class_key) >
684 sizeof(struct lockdep_map));
686 key = lock->key->subkeys + subclass;
688 hash_head = classhashentry(key);
691 * We do an RCU walk of the hash, see lockdep_free_key_range().
693 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
696 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
697 if (class->key == key) {
699 * Huh! same key, different name? Did someone trample
700 * on some memory? We're most confused.
702 WARN_ON_ONCE(class->name != lock->name);
711 * Static locks do not have their class-keys yet - for them the key is
712 * the lock object itself. If the lock is in the per cpu area, the
713 * canonical address of the lock (per cpu offset removed) is used.
715 static bool assign_lock_key(struct lockdep_map *lock)
717 unsigned long can_addr, addr = (unsigned long)lock;
719 if (__is_kernel_percpu_address(addr, &can_addr))
720 lock->key = (void *)can_addr;
721 else if (__is_module_percpu_address(addr, &can_addr))
722 lock->key = (void *)can_addr;
723 else if (static_obj(lock))
724 lock->key = (void *)lock;
726 /* Debug-check: all keys must be persistent! */
728 pr_err("INFO: trying to register non-static key.\n");
729 pr_err("the code is fine but needs lockdep annotation.\n");
730 pr_err("turning off the locking correctness validator.\n");
739 * Initialize the lock_classes[] array elements.
741 static void init_data_structures_once(void)
743 static bool initialization_happened;
746 if (likely(initialization_happened))
749 initialization_happened = true;
751 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
752 INIT_LIST_HEAD(&lock_classes[i].locks_after);
753 INIT_LIST_HEAD(&lock_classes[i].locks_before);
758 * Register a lock's class in the hash-table, if the class is not present
759 * yet. Otherwise we look it up. We cache the result in the lock object
760 * itself, so actual lookup of the hash should be once per lock object.
762 static struct lock_class *
763 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
765 struct lockdep_subclass_key *key;
766 struct hlist_head *hash_head;
767 struct lock_class *class;
769 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
771 class = look_up_lock_class(lock, subclass);
773 goto out_set_class_cache;
776 if (!assign_lock_key(lock))
778 } else if (!static_obj(lock->key)) {
782 key = lock->key->subkeys + subclass;
783 hash_head = classhashentry(key);
789 * We have to do the hash-walk again, to avoid races
792 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
793 if (class->key == key)
797 init_data_structures_once();
800 * Allocate a new key from the static array, and add it to
803 if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
804 if (!debug_locks_off_graph_unlock()) {
808 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
812 class = lock_classes + nr_lock_classes++;
813 debug_atomic_inc(nr_unused_locks);
815 class->name = lock->name;
816 class->subclass = subclass;
817 WARN_ON_ONCE(!list_empty(&class->locks_before));
818 WARN_ON_ONCE(!list_empty(&class->locks_after));
819 class->name_version = count_matching_names(class);
821 * We use RCU's safe list-add method to make
822 * parallel walking of the hash-list safe:
824 hlist_add_head_rcu(&class->hash_entry, hash_head);
826 * Add it to the global list of classes:
828 list_add_tail(&class->lock_entry, &all_lock_classes);
830 if (verbose(class)) {
833 printk("\nnew class %px: %s", class->key, class->name);
834 if (class->name_version > 1)
835 printk(KERN_CONT "#%d", class->name_version);
836 printk(KERN_CONT "\n");
847 if (!subclass || force)
848 lock->class_cache[0] = class;
849 else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
850 lock->class_cache[subclass] = class;
853 * Hash collision, did we smoke some? We found a class with a matching
854 * hash but the subclass -- which is hashed in -- didn't match.
856 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
862 #ifdef CONFIG_PROVE_LOCKING
864 * Allocate a lockdep entry. (assumes the graph_lock held, returns
865 * with NULL on failure)
867 static struct lock_list *alloc_list_entry(void)
869 if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
870 if (!debug_locks_off_graph_unlock())
873 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
877 return list_entries + nr_list_entries++;
881 * Add a new dependency to the head of the list:
883 static int add_lock_to_list(struct lock_class *this,
884 struct lock_class *links_to, struct list_head *head,
885 unsigned long ip, int distance,
886 struct stack_trace *trace)
888 struct lock_list *entry;
890 * Lock not present yet - get a new dependency struct and
891 * add it to the list:
893 entry = alloc_list_entry();
898 entry->links_to = links_to;
899 entry->distance = distance;
900 entry->trace = *trace;
902 * Both allocation and removal are done under the graph lock; but
903 * iteration is under RCU-sched; see look_up_lock_class() and
904 * lockdep_free_key_range().
906 list_add_tail_rcu(&entry->entry, head);
912 * For good efficiency of modular, we use power of 2
914 #define MAX_CIRCULAR_QUEUE_SIZE 4096UL
915 #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
918 * The circular_queue and helpers is used to implement the
919 * breadth-first search(BFS)algorithem, by which we can build
920 * the shortest path from the next lock to be acquired to the
921 * previous held lock if there is a circular between them.
923 struct circular_queue {
924 unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];
925 unsigned int front, rear;
928 static struct circular_queue lock_cq;
930 unsigned int max_bfs_queue_depth;
932 static unsigned int lockdep_dependency_gen_id;
934 static inline void __cq_init(struct circular_queue *cq)
936 cq->front = cq->rear = 0;
937 lockdep_dependency_gen_id++;
940 static inline int __cq_empty(struct circular_queue *cq)
942 return (cq->front == cq->rear);
945 static inline int __cq_full(struct circular_queue *cq)
947 return ((cq->rear + 1) & CQ_MASK) == cq->front;
950 static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
955 cq->element[cq->rear] = elem;
956 cq->rear = (cq->rear + 1) & CQ_MASK;
960 static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
965 *elem = cq->element[cq->front];
966 cq->front = (cq->front + 1) & CQ_MASK;
970 static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
972 return (cq->rear - cq->front) & CQ_MASK;
975 static inline void mark_lock_accessed(struct lock_list *lock,
976 struct lock_list *parent)
980 nr = lock - list_entries;
981 WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */
982 lock->parent = parent;
983 lock->class->dep_gen_id = lockdep_dependency_gen_id;
986 static inline unsigned long lock_accessed(struct lock_list *lock)
990 nr = lock - list_entries;
991 WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */
992 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
995 static inline struct lock_list *get_lock_parent(struct lock_list *child)
997 return child->parent;
1000 static inline int get_lock_depth(struct lock_list *child)
1003 struct lock_list *parent;
1005 while ((parent = get_lock_parent(child))) {
1012 static int __bfs(struct lock_list *source_entry,
1014 int (*match)(struct lock_list *entry, void *data),
1015 struct lock_list **target_entry,
1018 struct lock_list *entry;
1019 struct list_head *head;
1020 struct circular_queue *cq = &lock_cq;
1023 if (match(source_entry, data)) {
1024 *target_entry = source_entry;
1030 head = &source_entry->class->locks_after;
1032 head = &source_entry->class->locks_before;
1034 if (list_empty(head))
1038 __cq_enqueue(cq, (unsigned long)source_entry);
1040 while (!__cq_empty(cq)) {
1041 struct lock_list *lock;
1043 __cq_dequeue(cq, (unsigned long *)&lock);
1051 head = &lock->class->locks_after;
1053 head = &lock->class->locks_before;
1055 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1057 list_for_each_entry_rcu(entry, head, entry) {
1058 if (!lock_accessed(entry)) {
1059 unsigned int cq_depth;
1060 mark_lock_accessed(entry, lock);
1061 if (match(entry, data)) {
1062 *target_entry = entry;
1067 if (__cq_enqueue(cq, (unsigned long)entry)) {
1071 cq_depth = __cq_get_elem_count(cq);
1072 if (max_bfs_queue_depth < cq_depth)
1073 max_bfs_queue_depth = cq_depth;
1081 static inline int __bfs_forwards(struct lock_list *src_entry,
1083 int (*match)(struct lock_list *entry, void *data),
1084 struct lock_list **target_entry)
1086 return __bfs(src_entry, data, match, target_entry, 1);
1090 static inline int __bfs_backwards(struct lock_list *src_entry,
1092 int (*match)(struct lock_list *entry, void *data),
1093 struct lock_list **target_entry)
1095 return __bfs(src_entry, data, match, target_entry, 0);
1100 * Recursive, forwards-direction lock-dependency checking, used for
1101 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
1106 * Print a dependency chain entry (this is only done when a deadlock
1107 * has been detected):
1110 print_circular_bug_entry(struct lock_list *target, int depth)
1112 if (debug_locks_silent)
1114 printk("\n-> #%u", depth);
1115 print_lock_name(target->class);
1116 printk(KERN_CONT ":\n");
1117 print_stack_trace(&target->trace, 6);
1123 print_circular_lock_scenario(struct held_lock *src,
1124 struct held_lock *tgt,
1125 struct lock_list *prt)
1127 struct lock_class *source = hlock_class(src);
1128 struct lock_class *target = hlock_class(tgt);
1129 struct lock_class *parent = prt->class;
1132 * A direct locking problem where unsafe_class lock is taken
1133 * directly by safe_class lock, then all we need to show
1134 * is the deadlock scenario, as it is obvious that the
1135 * unsafe lock is taken under the safe lock.
1137 * But if there is a chain instead, where the safe lock takes
1138 * an intermediate lock (middle_class) where this lock is
1139 * not the same as the safe lock, then the lock chain is
1140 * used to describe the problem. Otherwise we would need
1141 * to show a different CPU case for each link in the chain
1142 * from the safe_class lock to the unsafe_class lock.
1144 if (parent != source) {
1145 printk("Chain exists of:\n ");
1146 __print_lock_name(source);
1147 printk(KERN_CONT " --> ");
1148 __print_lock_name(parent);
1149 printk(KERN_CONT " --> ");
1150 __print_lock_name(target);
1151 printk(KERN_CONT "\n\n");
1154 printk(" Possible unsafe locking scenario:\n\n");
1155 printk(" CPU0 CPU1\n");
1156 printk(" ---- ----\n");
1158 __print_lock_name(target);
1159 printk(KERN_CONT ");\n");
1161 __print_lock_name(parent);
1162 printk(KERN_CONT ");\n");
1164 __print_lock_name(target);
1165 printk(KERN_CONT ");\n");
1167 __print_lock_name(source);
1168 printk(KERN_CONT ");\n");
1169 printk("\n *** DEADLOCK ***\n\n");
1173 * When a circular dependency is detected, print the
1177 print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1178 struct held_lock *check_src,
1179 struct held_lock *check_tgt)
1181 struct task_struct *curr = current;
1183 if (debug_locks_silent)
1187 pr_warn("======================================================\n");
1188 pr_warn("WARNING: possible circular locking dependency detected\n");
1189 print_kernel_ident();
1190 pr_warn("------------------------------------------------------\n");
1191 pr_warn("%s/%d is trying to acquire lock:\n",
1192 curr->comm, task_pid_nr(curr));
1193 print_lock(check_src);
1195 pr_warn("\nbut task is already holding lock:\n");
1197 print_lock(check_tgt);
1198 pr_warn("\nwhich lock already depends on the new lock.\n\n");
1199 pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
1201 print_circular_bug_entry(entry, depth);
1206 static inline int class_equal(struct lock_list *entry, void *data)
1208 return entry->class == data;
1211 static noinline int print_circular_bug(struct lock_list *this,
1212 struct lock_list *target,
1213 struct held_lock *check_src,
1214 struct held_lock *check_tgt,
1215 struct stack_trace *trace)
1217 struct task_struct *curr = current;
1218 struct lock_list *parent;
1219 struct lock_list *first_parent;
1222 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1225 if (!save_trace(&this->trace))
1228 depth = get_lock_depth(target);
1230 print_circular_bug_header(target, depth, check_src, check_tgt);
1232 parent = get_lock_parent(target);
1233 first_parent = parent;
1236 print_circular_bug_entry(parent, --depth);
1237 parent = get_lock_parent(parent);
1240 printk("\nother info that might help us debug this:\n\n");
1241 print_circular_lock_scenario(check_src, check_tgt,
1244 lockdep_print_held_locks(curr);
1246 printk("\nstack backtrace:\n");
1252 static noinline int print_bfs_bug(int ret)
1254 if (!debug_locks_off_graph_unlock())
1258 * Breadth-first-search failed, graph got corrupted?
1260 WARN(1, "lockdep bfs error:%d\n", ret);
1265 static int noop_count(struct lock_list *entry, void *data)
1267 (*(unsigned long *)data)++;
1271 static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
1273 unsigned long count = 0;
1274 struct lock_list *uninitialized_var(target_entry);
1276 __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
1280 unsigned long lockdep_count_forward_deps(struct lock_class *class)
1282 unsigned long ret, flags;
1283 struct lock_list this;
1288 raw_local_irq_save(flags);
1289 arch_spin_lock(&lockdep_lock);
1290 ret = __lockdep_count_forward_deps(&this);
1291 arch_spin_unlock(&lockdep_lock);
1292 raw_local_irq_restore(flags);
1297 static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
1299 unsigned long count = 0;
1300 struct lock_list *uninitialized_var(target_entry);
1302 __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
1307 unsigned long lockdep_count_backward_deps(struct lock_class *class)
1309 unsigned long ret, flags;
1310 struct lock_list this;
1315 raw_local_irq_save(flags);
1316 arch_spin_lock(&lockdep_lock);
1317 ret = __lockdep_count_backward_deps(&this);
1318 arch_spin_unlock(&lockdep_lock);
1319 raw_local_irq_restore(flags);
1325 * Prove that the dependency graph starting at <entry> can not
1326 * lead to <target>. Print an error and return 0 if it does.
1329 check_noncircular(struct lock_list *root, struct lock_class *target,
1330 struct lock_list **target_entry)
1334 debug_atomic_inc(nr_cyclic_checks);
1336 result = __bfs_forwards(root, target, class_equal, target_entry);
1342 check_redundant(struct lock_list *root, struct lock_class *target,
1343 struct lock_list **target_entry)
1347 debug_atomic_inc(nr_redundant_checks);
1349 result = __bfs_forwards(root, target, class_equal, target_entry);
1354 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1356 * Forwards and backwards subgraph searching, for the purposes of
1357 * proving that two subgraphs can be connected by a new dependency
1358 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1361 static inline int usage_match(struct lock_list *entry, void *bit)
1363 return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
1369 * Find a node in the forwards-direction dependency sub-graph starting
1370 * at @root->class that matches @bit.
1372 * Return 0 if such a node exists in the subgraph, and put that node
1373 * into *@target_entry.
1375 * Return 1 otherwise and keep *@target_entry unchanged.
1376 * Return <0 on error.
1379 find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
1380 struct lock_list **target_entry)
1384 debug_atomic_inc(nr_find_usage_forwards_checks);
1386 result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
1392 * Find a node in the backwards-direction dependency sub-graph starting
1393 * at @root->class that matches @bit.
1395 * Return 0 if such a node exists in the subgraph, and put that node
1396 * into *@target_entry.
1398 * Return 1 otherwise and keep *@target_entry unchanged.
1399 * Return <0 on error.
1402 find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
1403 struct lock_list **target_entry)
1407 debug_atomic_inc(nr_find_usage_backwards_checks);
1409 result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
1414 static void print_lock_class_header(struct lock_class *class, int depth)
1418 printk("%*s->", depth, "");
1419 print_lock_name(class);
1420 #ifdef CONFIG_DEBUG_LOCKDEP
1421 printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
1423 printk(KERN_CONT " {\n");
1425 for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
1426 if (class->usage_mask & (1 << bit)) {
1429 len += printk("%*s %s", depth, "", usage_str[bit]);
1430 len += printk(KERN_CONT " at:\n");
1431 print_stack_trace(class->usage_traces + bit, len);
1434 printk("%*s }\n", depth, "");
1436 printk("%*s ... key at: [<%px>] %pS\n",
1437 depth, "", class->key, class->key);
1441 * printk the shortest lock dependencies from @start to @end in reverse order:
1444 print_shortest_lock_dependencies(struct lock_list *leaf,
1445 struct lock_list *root)
1447 struct lock_list *entry = leaf;
1450 /*compute depth from generated tree by BFS*/
1451 depth = get_lock_depth(leaf);
1454 print_lock_class_header(entry->class, depth);
1455 printk("%*s ... acquired at:\n", depth, "");
1456 print_stack_trace(&entry->trace, 2);
1459 if (depth == 0 && (entry != root)) {
1460 printk("lockdep:%s bad path found in chain graph\n", __func__);
1464 entry = get_lock_parent(entry);
1466 } while (entry && (depth >= 0));
1472 print_irq_lock_scenario(struct lock_list *safe_entry,
1473 struct lock_list *unsafe_entry,
1474 struct lock_class *prev_class,
1475 struct lock_class *next_class)
1477 struct lock_class *safe_class = safe_entry->class;
1478 struct lock_class *unsafe_class = unsafe_entry->class;
1479 struct lock_class *middle_class = prev_class;
1481 if (middle_class == safe_class)
1482 middle_class = next_class;
1485 * A direct locking problem where unsafe_class lock is taken
1486 * directly by safe_class lock, then all we need to show
1487 * is the deadlock scenario, as it is obvious that the
1488 * unsafe lock is taken under the safe lock.
1490 * But if there is a chain instead, where the safe lock takes
1491 * an intermediate lock (middle_class) where this lock is
1492 * not the same as the safe lock, then the lock chain is
1493 * used to describe the problem. Otherwise we would need
1494 * to show a different CPU case for each link in the chain
1495 * from the safe_class lock to the unsafe_class lock.
1497 if (middle_class != unsafe_class) {
1498 printk("Chain exists of:\n ");
1499 __print_lock_name(safe_class);
1500 printk(KERN_CONT " --> ");
1501 __print_lock_name(middle_class);
1502 printk(KERN_CONT " --> ");
1503 __print_lock_name(unsafe_class);
1504 printk(KERN_CONT "\n\n");
1507 printk(" Possible interrupt unsafe locking scenario:\n\n");
1508 printk(" CPU0 CPU1\n");
1509 printk(" ---- ----\n");
1511 __print_lock_name(unsafe_class);
1512 printk(KERN_CONT ");\n");
1513 printk(" local_irq_disable();\n");
1515 __print_lock_name(safe_class);
1516 printk(KERN_CONT ");\n");
1518 __print_lock_name(middle_class);
1519 printk(KERN_CONT ");\n");
1520 printk(" <Interrupt>\n");
1522 __print_lock_name(safe_class);
1523 printk(KERN_CONT ");\n");
1524 printk("\n *** DEADLOCK ***\n\n");
1528 print_bad_irq_dependency(struct task_struct *curr,
1529 struct lock_list *prev_root,
1530 struct lock_list *next_root,
1531 struct lock_list *backwards_entry,
1532 struct lock_list *forwards_entry,
1533 struct held_lock *prev,
1534 struct held_lock *next,
1535 enum lock_usage_bit bit1,
1536 enum lock_usage_bit bit2,
1537 const char *irqclass)
1539 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1543 pr_warn("=====================================================\n");
1544 pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
1545 irqclass, irqclass);
1546 print_kernel_ident();
1547 pr_warn("-----------------------------------------------------\n");
1548 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1549 curr->comm, task_pid_nr(curr),
1550 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1551 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1552 curr->hardirqs_enabled,
1553 curr->softirqs_enabled);
1556 pr_warn("\nand this task is already holding:\n");
1558 pr_warn("which would create a new lock dependency:\n");
1559 print_lock_name(hlock_class(prev));
1561 print_lock_name(hlock_class(next));
1564 pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
1566 print_lock_name(backwards_entry->class);
1567 pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
1569 print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
1571 pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
1572 print_lock_name(forwards_entry->class);
1573 pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
1576 print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
1578 pr_warn("\nother info that might help us debug this:\n\n");
1579 print_irq_lock_scenario(backwards_entry, forwards_entry,
1580 hlock_class(prev), hlock_class(next));
1582 lockdep_print_held_locks(curr);
1584 pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
1585 if (!save_trace(&prev_root->trace))
1587 print_shortest_lock_dependencies(backwards_entry, prev_root);
1589 pr_warn("\nthe dependencies between the lock to be acquired");
1590 pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
1591 if (!save_trace(&next_root->trace))
1593 print_shortest_lock_dependencies(forwards_entry, next_root);
1595 pr_warn("\nstack backtrace:\n");
1602 check_usage(struct task_struct *curr, struct held_lock *prev,
1603 struct held_lock *next, enum lock_usage_bit bit_backwards,
1604 enum lock_usage_bit bit_forwards, const char *irqclass)
1607 struct lock_list this, that;
1608 struct lock_list *uninitialized_var(target_entry);
1609 struct lock_list *uninitialized_var(target_entry1);
1613 this.class = hlock_class(prev);
1614 ret = find_usage_backwards(&this, bit_backwards, &target_entry);
1616 return print_bfs_bug(ret);
1621 that.class = hlock_class(next);
1622 ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
1624 return print_bfs_bug(ret);
1628 return print_bad_irq_dependency(curr, &this, &that,
1629 target_entry, target_entry1,
1631 bit_backwards, bit_forwards, irqclass);
1634 static const char *state_names[] = {
1635 #define LOCKDEP_STATE(__STATE) \
1636 __stringify(__STATE),
1637 #include "lockdep_states.h"
1638 #undef LOCKDEP_STATE
1641 static const char *state_rnames[] = {
1642 #define LOCKDEP_STATE(__STATE) \
1643 __stringify(__STATE)"-READ",
1644 #include "lockdep_states.h"
1645 #undef LOCKDEP_STATE
1648 static inline const char *state_name(enum lock_usage_bit bit)
1650 return (bit & LOCK_USAGE_READ_MASK) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1653 static int exclusive_bit(int new_bit)
1655 int state = new_bit & LOCK_USAGE_STATE_MASK;
1656 int dir = new_bit & LOCK_USAGE_DIR_MASK;
1659 * keep state, bit flip the direction and strip read.
1661 return state | (dir ^ LOCK_USAGE_DIR_MASK);
1664 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1665 struct held_lock *next, enum lock_usage_bit bit)
1668 * Prove that the new dependency does not connect a hardirq-safe
1669 * lock with a hardirq-unsafe lock - to achieve this we search
1670 * the backwards-subgraph starting at <prev>, and the
1671 * forwards-subgraph starting at <next>:
1673 if (!check_usage(curr, prev, next, bit,
1674 exclusive_bit(bit), state_name(bit)))
1680 * Prove that the new dependency does not connect a hardirq-safe-read
1681 * lock with a hardirq-unsafe lock - to achieve this we search
1682 * the backwards-subgraph starting at <prev>, and the
1683 * forwards-subgraph starting at <next>:
1685 if (!check_usage(curr, prev, next, bit,
1686 exclusive_bit(bit), state_name(bit)))
1693 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1694 struct held_lock *next)
1696 #define LOCKDEP_STATE(__STATE) \
1697 if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1699 #include "lockdep_states.h"
1700 #undef LOCKDEP_STATE
1705 static void inc_chains(void)
1707 if (current->hardirq_context)
1708 nr_hardirq_chains++;
1710 if (current->softirq_context)
1711 nr_softirq_chains++;
1713 nr_process_chains++;
1720 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1721 struct held_lock *next)
1726 static inline void inc_chains(void)
1728 nr_process_chains++;
1734 print_deadlock_scenario(struct held_lock *nxt,
1735 struct held_lock *prv)
1737 struct lock_class *next = hlock_class(nxt);
1738 struct lock_class *prev = hlock_class(prv);
1740 printk(" Possible unsafe locking scenario:\n\n");
1744 __print_lock_name(prev);
1745 printk(KERN_CONT ");\n");
1747 __print_lock_name(next);
1748 printk(KERN_CONT ");\n");
1749 printk("\n *** DEADLOCK ***\n\n");
1750 printk(" May be due to missing lock nesting notation\n\n");
1754 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1755 struct held_lock *next)
1757 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1761 pr_warn("============================================\n");
1762 pr_warn("WARNING: possible recursive locking detected\n");
1763 print_kernel_ident();
1764 pr_warn("--------------------------------------------\n");
1765 pr_warn("%s/%d is trying to acquire lock:\n",
1766 curr->comm, task_pid_nr(curr));
1768 pr_warn("\nbut task is already holding lock:\n");
1771 pr_warn("\nother info that might help us debug this:\n");
1772 print_deadlock_scenario(next, prev);
1773 lockdep_print_held_locks(curr);
1775 pr_warn("\nstack backtrace:\n");
1782 * Check whether we are holding such a class already.
1784 * (Note that this has to be done separately, because the graph cannot
1785 * detect such classes of deadlocks.)
1787 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1790 check_deadlock(struct task_struct *curr, struct held_lock *next,
1791 struct lockdep_map *next_instance, int read)
1793 struct held_lock *prev;
1794 struct held_lock *nest = NULL;
1797 for (i = 0; i < curr->lockdep_depth; i++) {
1798 prev = curr->held_locks + i;
1800 if (prev->instance == next->nest_lock)
1803 if (hlock_class(prev) != hlock_class(next))
1807 * Allow read-after-read recursion of the same
1808 * lock class (i.e. read_lock(lock)+read_lock(lock)):
1810 if ((read == 2) && prev->read)
1814 * We're holding the nest_lock, which serializes this lock's
1815 * nesting behaviour.
1820 return print_deadlock_bug(curr, prev, next);
1826 * There was a chain-cache miss, and we are about to add a new dependency
1827 * to a previous lock. We recursively validate the following rules:
1829 * - would the adding of the <prev> -> <next> dependency create a
1830 * circular dependency in the graph? [== circular deadlock]
1832 * - does the new prev->next dependency connect any hardirq-safe lock
1833 * (in the full backwards-subgraph starting at <prev>) with any
1834 * hardirq-unsafe lock (in the full forwards-subgraph starting at
1835 * <next>)? [== illegal lock inversion with hardirq contexts]
1837 * - does the new prev->next dependency connect any softirq-safe lock
1838 * (in the full backwards-subgraph starting at <prev>) with any
1839 * softirq-unsafe lock (in the full forwards-subgraph starting at
1840 * <next>)? [== illegal lock inversion with softirq contexts]
1842 * any of these scenarios could lead to a deadlock.
1844 * Then if all the validations pass, we add the forwards and backwards
1848 check_prev_add(struct task_struct *curr, struct held_lock *prev,
1849 struct held_lock *next, int distance, struct stack_trace *trace,
1850 int (*save)(struct stack_trace *trace))
1852 struct lock_list *uninitialized_var(target_entry);
1853 struct lock_list *entry;
1854 struct lock_list this;
1858 * Prove that the new <prev> -> <next> dependency would not
1859 * create a circular dependency in the graph. (We do this by
1860 * forward-recursing into the graph starting at <next>, and
1861 * checking whether we can reach <prev>.)
1863 * We are using global variables to control the recursion, to
1864 * keep the stackframe size of the recursive functions low:
1866 this.class = hlock_class(next);
1868 ret = check_noncircular(&this, hlock_class(prev), &target_entry);
1869 if (unlikely(!ret)) {
1870 if (!trace->entries) {
1872 * If @save fails here, the printing might trigger
1873 * a WARN but because of the !nr_entries it should
1874 * not do bad things.
1878 return print_circular_bug(&this, target_entry, next, prev, trace);
1880 else if (unlikely(ret < 0))
1881 return print_bfs_bug(ret);
1883 if (!check_prev_add_irq(curr, prev, next))
1887 * For recursive read-locks we do all the dependency checks,
1888 * but we dont store read-triggered dependencies (only
1889 * write-triggered dependencies). This ensures that only the
1890 * write-side dependencies matter, and that if for example a
1891 * write-lock never takes any other locks, then the reads are
1892 * equivalent to a NOP.
1894 if (next->read == 2 || prev->read == 2)
1897 * Is the <prev> -> <next> dependency already present?
1899 * (this may occur even though this is a new chain: consider
1900 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1901 * chains - the second one will be new, but L1 already has
1902 * L2 added to its dependency list, due to the first chain.)
1904 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1905 if (entry->class == hlock_class(next)) {
1907 entry->distance = 1;
1913 * Is the <prev> -> <next> link redundant?
1915 this.class = hlock_class(prev);
1917 ret = check_redundant(&this, hlock_class(next), &target_entry);
1919 debug_atomic_inc(nr_redundant);
1923 return print_bfs_bug(ret);
1926 if (!trace->entries && !save(trace))
1930 * Ok, all validations passed, add the new lock
1931 * to the previous lock's dependency list:
1933 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
1934 &hlock_class(prev)->locks_after,
1935 next->acquire_ip, distance, trace);
1940 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
1941 &hlock_class(next)->locks_before,
1942 next->acquire_ip, distance, trace);
1950 * Add the dependency to all directly-previous locks that are 'relevant'.
1951 * The ones that are relevant are (in increasing distance from curr):
1952 * all consecutive trylock entries and the final non-trylock entry - or
1953 * the end of this context's lock-chain - whichever comes first.
1956 check_prevs_add(struct task_struct *curr, struct held_lock *next)
1958 int depth = curr->lockdep_depth;
1959 struct held_lock *hlock;
1960 struct stack_trace trace = {
1970 * Depth must not be zero for a non-head lock:
1975 * At least two relevant locks must exist for this
1978 if (curr->held_locks[depth].irq_context !=
1979 curr->held_locks[depth-1].irq_context)
1983 int distance = curr->lockdep_depth - depth + 1;
1984 hlock = curr->held_locks + depth - 1;
1987 * Only non-recursive-read entries get new dependencies
1990 if (hlock->read != 2 && hlock->check) {
1991 int ret = check_prev_add(curr, hlock, next, distance, &trace, save_trace);
1996 * Stop after the first non-trylock entry,
1997 * as non-trylock entries have added their
1998 * own direct dependencies already, so this
1999 * lock is connected to them indirectly:
2001 if (!hlock->trylock)
2007 * End of lock-stack?
2012 * Stop the search if we cross into another context:
2014 if (curr->held_locks[depth].irq_context !=
2015 curr->held_locks[depth-1].irq_context)
2020 if (!debug_locks_off_graph_unlock())
2024 * Clearly we all shouldn't be here, but since we made it we
2025 * can reliable say we messed up our state. See the above two
2026 * gotos for reasons why we could possibly end up here.
2033 unsigned long nr_lock_chains;
2034 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
2035 int nr_chain_hlocks;
2036 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
2038 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
2040 return lock_classes + chain_hlocks[chain->base + i];
2044 * Returns the index of the first held_lock of the current chain
2046 static inline int get_first_held_lock(struct task_struct *curr,
2047 struct held_lock *hlock)
2050 struct held_lock *hlock_curr;
2052 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
2053 hlock_curr = curr->held_locks + i;
2054 if (hlock_curr->irq_context != hlock->irq_context)
2062 #ifdef CONFIG_DEBUG_LOCKDEP
2064 * Returns the next chain_key iteration
2066 static u64 print_chain_key_iteration(int class_idx, u64 chain_key)
2068 u64 new_chain_key = iterate_chain_key(chain_key, class_idx);
2070 printk(" class_idx:%d -> chain_key:%016Lx",
2072 (unsigned long long)new_chain_key);
2073 return new_chain_key;
2077 print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
2079 struct held_lock *hlock;
2081 int depth = curr->lockdep_depth;
2084 printk("depth: %u\n", depth + 1);
2085 for (i = get_first_held_lock(curr, hlock_next); i < depth; i++) {
2086 hlock = curr->held_locks + i;
2087 chain_key = print_chain_key_iteration(hlock->class_idx, chain_key);
2092 print_chain_key_iteration(hlock_next->class_idx, chain_key);
2093 print_lock(hlock_next);
2096 static void print_chain_keys_chain(struct lock_chain *chain)
2102 printk("depth: %u\n", chain->depth);
2103 for (i = 0; i < chain->depth; i++) {
2104 class_id = chain_hlocks[chain->base + i];
2105 chain_key = print_chain_key_iteration(class_id + 1, chain_key);
2107 print_lock_name(lock_classes + class_id);
2112 static void print_collision(struct task_struct *curr,
2113 struct held_lock *hlock_next,
2114 struct lock_chain *chain)
2117 pr_warn("============================\n");
2118 pr_warn("WARNING: chain_key collision\n");
2119 print_kernel_ident();
2120 pr_warn("----------------------------\n");
2121 pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
2122 pr_warn("Hash chain already cached but the contents don't match!\n");
2124 pr_warn("Held locks:");
2125 print_chain_keys_held_locks(curr, hlock_next);
2127 pr_warn("Locks in cached chain:");
2128 print_chain_keys_chain(chain);
2130 pr_warn("\nstack backtrace:\n");
2136 * Checks whether the chain and the current held locks are consistent
2137 * in depth and also in content. If they are not it most likely means
2138 * that there was a collision during the calculation of the chain_key.
2139 * Returns: 0 not passed, 1 passed
2141 static int check_no_collision(struct task_struct *curr,
2142 struct held_lock *hlock,
2143 struct lock_chain *chain)
2145 #ifdef CONFIG_DEBUG_LOCKDEP
2148 i = get_first_held_lock(curr, hlock);
2150 if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
2151 print_collision(curr, hlock, chain);
2155 for (j = 0; j < chain->depth - 1; j++, i++) {
2156 id = curr->held_locks[i].class_idx - 1;
2158 if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
2159 print_collision(curr, hlock, chain);
2168 * Adds a dependency chain into chain hashtable. And must be called with
2171 * Return 0 if fail, and graph_lock is released.
2172 * Return 1 if succeed, with graph_lock held.
2174 static inline int add_chain_cache(struct task_struct *curr,
2175 struct held_lock *hlock,
2178 struct lock_class *class = hlock_class(hlock);
2179 struct hlist_head *hash_head = chainhashentry(chain_key);
2180 struct lock_chain *chain;
2184 * Allocate a new chain entry from the static array, and add
2189 * We might need to take the graph lock, ensure we've got IRQs
2190 * disabled to make this an IRQ-safe lock.. for recursion reasons
2191 * lockdep won't complain about its own locking errors.
2193 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2196 if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
2197 if (!debug_locks_off_graph_unlock())
2200 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
2204 chain = lock_chains + nr_lock_chains++;
2205 chain->chain_key = chain_key;
2206 chain->irq_context = hlock->irq_context;
2207 i = get_first_held_lock(curr, hlock);
2208 chain->depth = curr->lockdep_depth + 1 - i;
2210 BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
2211 BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
2212 BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
2214 if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
2215 chain->base = nr_chain_hlocks;
2216 for (j = 0; j < chain->depth - 1; j++, i++) {
2217 int lock_id = curr->held_locks[i].class_idx - 1;
2218 chain_hlocks[chain->base + j] = lock_id;
2220 chain_hlocks[chain->base + j] = class - lock_classes;
2221 nr_chain_hlocks += chain->depth;
2223 if (!debug_locks_off_graph_unlock())
2226 print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
2231 hlist_add_head_rcu(&chain->entry, hash_head);
2232 debug_atomic_inc(chain_lookup_misses);
2239 * Look up a dependency chain.
2241 static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
2243 struct hlist_head *hash_head = chainhashentry(chain_key);
2244 struct lock_chain *chain;
2247 * We can walk it lock-free, because entries only get added
2250 hlist_for_each_entry_rcu(chain, hash_head, entry) {
2251 if (chain->chain_key == chain_key) {
2252 debug_atomic_inc(chain_lookup_hits);
2260 * If the key is not present yet in dependency chain cache then
2261 * add it and return 1 - in this case the new dependency chain is
2262 * validated. If the key is already hashed, return 0.
2263 * (On return with 1 graph_lock is held.)
2265 static inline int lookup_chain_cache_add(struct task_struct *curr,
2266 struct held_lock *hlock,
2269 struct lock_class *class = hlock_class(hlock);
2270 struct lock_chain *chain = lookup_chain_cache(chain_key);
2274 if (!check_no_collision(curr, hlock, chain))
2277 if (very_verbose(class)) {
2278 printk("\nhash chain already cached, key: "
2279 "%016Lx tail class: [%px] %s\n",
2280 (unsigned long long)chain_key,
2281 class->key, class->name);
2287 if (very_verbose(class)) {
2288 printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
2289 (unsigned long long)chain_key, class->key, class->name);
2296 * We have to walk the chain again locked - to avoid duplicates:
2298 chain = lookup_chain_cache(chain_key);
2304 if (!add_chain_cache(curr, hlock, chain_key))
2310 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
2311 struct held_lock *hlock, int chain_head, u64 chain_key)
2314 * Trylock needs to maintain the stack of held locks, but it
2315 * does not add new dependencies, because trylock can be done
2318 * We look up the chain_key and do the O(N^2) check and update of
2319 * the dependencies only if this is a new dependency chain.
2320 * (If lookup_chain_cache_add() return with 1 it acquires
2321 * graph_lock for us)
2323 if (!hlock->trylock && hlock->check &&
2324 lookup_chain_cache_add(curr, hlock, chain_key)) {
2326 * Check whether last held lock:
2328 * - is irq-safe, if this lock is irq-unsafe
2329 * - is softirq-safe, if this lock is hardirq-unsafe
2331 * And check whether the new lock's dependency graph
2332 * could lead back to the previous lock.
2334 * any of these scenarios could lead to a deadlock. If
2337 int ret = check_deadlock(curr, hlock, lock, hlock->read);
2342 * Mark recursive read, as we jump over it when
2343 * building dependencies (just like we jump over
2349 * Add dependency only if this lock is not the head
2350 * of the chain, and if it's not a secondary read-lock:
2352 if (!chain_head && ret != 2) {
2353 if (!check_prevs_add(curr, hlock))
2359 /* after lookup_chain_cache_add(): */
2360 if (unlikely(!debug_locks))
2367 static inline int validate_chain(struct task_struct *curr,
2368 struct lockdep_map *lock, struct held_lock *hlock,
2369 int chain_head, u64 chain_key)
2376 * We are building curr_chain_key incrementally, so double-check
2377 * it from scratch, to make sure that it's done correctly:
2379 static void check_chain_key(struct task_struct *curr)
2381 #ifdef CONFIG_DEBUG_LOCKDEP
2382 struct held_lock *hlock, *prev_hlock = NULL;
2386 for (i = 0; i < curr->lockdep_depth; i++) {
2387 hlock = curr->held_locks + i;
2388 if (chain_key != hlock->prev_chain_key) {
2391 * We got mighty confused, our chain keys don't match
2392 * with what we expect, someone trample on our task state?
2394 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
2395 curr->lockdep_depth, i,
2396 (unsigned long long)chain_key,
2397 (unsigned long long)hlock->prev_chain_key);
2401 * Whoops ran out of static storage again?
2403 if (DEBUG_LOCKS_WARN_ON(hlock->class_idx > MAX_LOCKDEP_KEYS))
2406 if (prev_hlock && (prev_hlock->irq_context !=
2407 hlock->irq_context))
2409 chain_key = iterate_chain_key(chain_key, hlock->class_idx);
2412 if (chain_key != curr->curr_chain_key) {
2415 * More smoking hash instead of calculating it, damn see these
2416 * numbers float.. I bet that a pink elephant stepped on my memory.
2418 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
2419 curr->lockdep_depth, i,
2420 (unsigned long long)chain_key,
2421 (unsigned long long)curr->curr_chain_key);
2427 print_usage_bug_scenario(struct held_lock *lock)
2429 struct lock_class *class = hlock_class(lock);
2431 printk(" Possible unsafe locking scenario:\n\n");
2435 __print_lock_name(class);
2436 printk(KERN_CONT ");\n");
2437 printk(" <Interrupt>\n");
2439 __print_lock_name(class);
2440 printk(KERN_CONT ");\n");
2441 printk("\n *** DEADLOCK ***\n\n");
2445 print_usage_bug(struct task_struct *curr, struct held_lock *this,
2446 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
2448 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2452 pr_warn("================================\n");
2453 pr_warn("WARNING: inconsistent lock state\n");
2454 print_kernel_ident();
2455 pr_warn("--------------------------------\n");
2457 pr_warn("inconsistent {%s} -> {%s} usage.\n",
2458 usage_str[prev_bit], usage_str[new_bit]);
2460 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
2461 curr->comm, task_pid_nr(curr),
2462 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
2463 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
2464 trace_hardirqs_enabled(curr),
2465 trace_softirqs_enabled(curr));
2468 pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
2469 print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
2471 print_irqtrace_events(curr);
2472 pr_warn("\nother info that might help us debug this:\n");
2473 print_usage_bug_scenario(this);
2475 lockdep_print_held_locks(curr);
2477 pr_warn("\nstack backtrace:\n");
2484 * Print out an error if an invalid bit is set:
2487 valid_state(struct task_struct *curr, struct held_lock *this,
2488 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
2490 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
2491 return print_usage_bug(curr, this, bad_bit, new_bit);
2495 static int mark_lock(struct task_struct *curr, struct held_lock *this,
2496 enum lock_usage_bit new_bit);
2498 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
2501 * print irq inversion bug:
2504 print_irq_inversion_bug(struct task_struct *curr,
2505 struct lock_list *root, struct lock_list *other,
2506 struct held_lock *this, int forwards,
2507 const char *irqclass)
2509 struct lock_list *entry = other;
2510 struct lock_list *middle = NULL;
2513 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2517 pr_warn("========================================================\n");
2518 pr_warn("WARNING: possible irq lock inversion dependency detected\n");
2519 print_kernel_ident();
2520 pr_warn("--------------------------------------------------------\n");
2521 pr_warn("%s/%d just changed the state of lock:\n",
2522 curr->comm, task_pid_nr(curr));
2525 pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
2527 pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
2528 print_lock_name(other->class);
2529 pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
2531 pr_warn("\nother info that might help us debug this:\n");
2533 /* Find a middle lock (if one exists) */
2534 depth = get_lock_depth(other);
2536 if (depth == 0 && (entry != root)) {
2537 pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
2541 entry = get_lock_parent(entry);
2543 } while (entry && entry != root && (depth >= 0));
2545 print_irq_lock_scenario(root, other,
2546 middle ? middle->class : root->class, other->class);
2548 print_irq_lock_scenario(other, root,
2549 middle ? middle->class : other->class, root->class);
2551 lockdep_print_held_locks(curr);
2553 pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
2554 if (!save_trace(&root->trace))
2556 print_shortest_lock_dependencies(other, root);
2558 pr_warn("\nstack backtrace:\n");
2565 * Prove that in the forwards-direction subgraph starting at <this>
2566 * there is no lock matching <mask>:
2569 check_usage_forwards(struct task_struct *curr, struct held_lock *this,
2570 enum lock_usage_bit bit, const char *irqclass)
2573 struct lock_list root;
2574 struct lock_list *uninitialized_var(target_entry);
2577 root.class = hlock_class(this);
2578 ret = find_usage_forwards(&root, bit, &target_entry);
2580 return print_bfs_bug(ret);
2584 return print_irq_inversion_bug(curr, &root, target_entry,
2589 * Prove that in the backwards-direction subgraph starting at <this>
2590 * there is no lock matching <mask>:
2593 check_usage_backwards(struct task_struct *curr, struct held_lock *this,
2594 enum lock_usage_bit bit, const char *irqclass)
2597 struct lock_list root;
2598 struct lock_list *uninitialized_var(target_entry);
2601 root.class = hlock_class(this);
2602 ret = find_usage_backwards(&root, bit, &target_entry);
2604 return print_bfs_bug(ret);
2608 return print_irq_inversion_bug(curr, &root, target_entry,
2612 void print_irqtrace_events(struct task_struct *curr)
2614 printk("irq event stamp: %u\n", curr->irq_events);
2615 printk("hardirqs last enabled at (%u): [<%px>] %pS\n",
2616 curr->hardirq_enable_event, (void *)curr->hardirq_enable_ip,
2617 (void *)curr->hardirq_enable_ip);
2618 printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
2619 curr->hardirq_disable_event, (void *)curr->hardirq_disable_ip,
2620 (void *)curr->hardirq_disable_ip);
2621 printk("softirqs last enabled at (%u): [<%px>] %pS\n",
2622 curr->softirq_enable_event, (void *)curr->softirq_enable_ip,
2623 (void *)curr->softirq_enable_ip);
2624 printk("softirqs last disabled at (%u): [<%px>] %pS\n",
2625 curr->softirq_disable_event, (void *)curr->softirq_disable_ip,
2626 (void *)curr->softirq_disable_ip);
2629 static int HARDIRQ_verbose(struct lock_class *class)
2632 return class_filter(class);
2637 static int SOFTIRQ_verbose(struct lock_class *class)
2640 return class_filter(class);
2645 #define STRICT_READ_CHECKS 1
2647 static int (*state_verbose_f[])(struct lock_class *class) = {
2648 #define LOCKDEP_STATE(__STATE) \
2650 #include "lockdep_states.h"
2651 #undef LOCKDEP_STATE
2654 static inline int state_verbose(enum lock_usage_bit bit,
2655 struct lock_class *class)
2657 return state_verbose_f[bit >> 2](class);
2660 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2661 enum lock_usage_bit bit, const char *name);
2664 mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2665 enum lock_usage_bit new_bit)
2667 int excl_bit = exclusive_bit(new_bit);
2668 int read = new_bit & LOCK_USAGE_READ_MASK;
2669 int dir = new_bit & LOCK_USAGE_DIR_MASK;
2672 * mark USED_IN has to look forwards -- to ensure no dependency
2673 * has ENABLED state, which would allow recursion deadlocks.
2675 * mark ENABLED has to look backwards -- to ensure no dependee
2676 * has USED_IN state, which, again, would allow recursion deadlocks.
2678 check_usage_f usage = dir ?
2679 check_usage_backwards : check_usage_forwards;
2682 * Validate that this particular lock does not have conflicting
2685 if (!valid_state(curr, this, new_bit, excl_bit))
2689 * Validate that the lock dependencies don't have conflicting usage
2692 if ((!read || !dir || STRICT_READ_CHECKS) &&
2693 !usage(curr, this, excl_bit, state_name(new_bit & ~LOCK_USAGE_READ_MASK)))
2697 * Check for read in write conflicts
2700 if (!valid_state(curr, this, new_bit, excl_bit + LOCK_USAGE_READ_MASK))
2703 if (STRICT_READ_CHECKS &&
2704 !usage(curr, this, excl_bit + LOCK_USAGE_READ_MASK,
2705 state_name(new_bit + LOCK_USAGE_READ_MASK)))
2709 if (state_verbose(new_bit, hlock_class(this)))
2716 * Mark all held locks with a usage bit:
2719 mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
2721 struct held_lock *hlock;
2724 for (i = 0; i < curr->lockdep_depth; i++) {
2725 enum lock_usage_bit hlock_bit = base_bit;
2726 hlock = curr->held_locks + i;
2729 hlock_bit += LOCK_USAGE_READ_MASK;
2731 BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
2736 if (!mark_lock(curr, hlock, hlock_bit))
2744 * Hardirqs will be enabled:
2746 static void __trace_hardirqs_on_caller(unsigned long ip)
2748 struct task_struct *curr = current;
2750 /* we'll do an OFF -> ON transition: */
2751 curr->hardirqs_enabled = 1;
2754 * We are going to turn hardirqs on, so set the
2755 * usage bit for all held locks:
2757 if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
2760 * If we have softirqs enabled, then set the usage
2761 * bit for all held locks. (disabled hardirqs prevented
2762 * this bit from being set before)
2764 if (curr->softirqs_enabled)
2765 if (!mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ))
2768 curr->hardirq_enable_ip = ip;
2769 curr->hardirq_enable_event = ++curr->irq_events;
2770 debug_atomic_inc(hardirqs_on_events);
2773 void lockdep_hardirqs_on(unsigned long ip)
2775 if (unlikely(!debug_locks || current->lockdep_recursion))
2778 if (unlikely(current->hardirqs_enabled)) {
2780 * Neither irq nor preemption are disabled here
2781 * so this is racy by nature but losing one hit
2782 * in a stat is not a big deal.
2784 __debug_atomic_inc(redundant_hardirqs_on);
2789 * We're enabling irqs and according to our state above irqs weren't
2790 * already enabled, yet we find the hardware thinks they are in fact
2791 * enabled.. someone messed up their IRQ state tracing.
2793 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2797 * See the fine text that goes along with this variable definition.
2799 if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
2803 * Can't allow enabling interrupts while in an interrupt handler,
2804 * that's general bad form and such. Recursion, limited stack etc..
2806 if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2809 current->lockdep_recursion = 1;
2810 __trace_hardirqs_on_caller(ip);
2811 current->lockdep_recursion = 0;
2815 * Hardirqs were disabled:
2817 void lockdep_hardirqs_off(unsigned long ip)
2819 struct task_struct *curr = current;
2821 if (unlikely(!debug_locks || current->lockdep_recursion))
2825 * So we're supposed to get called after you mask local IRQs, but for
2826 * some reason the hardware doesn't quite think you did a proper job.
2828 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2831 if (curr->hardirqs_enabled) {
2833 * We have done an ON -> OFF transition:
2835 curr->hardirqs_enabled = 0;
2836 curr->hardirq_disable_ip = ip;
2837 curr->hardirq_disable_event = ++curr->irq_events;
2838 debug_atomic_inc(hardirqs_off_events);
2840 debug_atomic_inc(redundant_hardirqs_off);
2844 * Softirqs will be enabled:
2846 void trace_softirqs_on(unsigned long ip)
2848 struct task_struct *curr = current;
2850 if (unlikely(!debug_locks || current->lockdep_recursion))
2854 * We fancy IRQs being disabled here, see softirq.c, avoids
2855 * funny state and nesting things.
2857 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2860 if (curr->softirqs_enabled) {
2861 debug_atomic_inc(redundant_softirqs_on);
2865 current->lockdep_recursion = 1;
2867 * We'll do an OFF -> ON transition:
2869 curr->softirqs_enabled = 1;
2870 curr->softirq_enable_ip = ip;
2871 curr->softirq_enable_event = ++curr->irq_events;
2872 debug_atomic_inc(softirqs_on_events);
2874 * We are going to turn softirqs on, so set the
2875 * usage bit for all held locks, if hardirqs are
2878 if (curr->hardirqs_enabled)
2879 mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
2880 current->lockdep_recursion = 0;
2884 * Softirqs were disabled:
2886 void trace_softirqs_off(unsigned long ip)
2888 struct task_struct *curr = current;
2890 if (unlikely(!debug_locks || current->lockdep_recursion))
2894 * We fancy IRQs being disabled here, see softirq.c
2896 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2899 if (curr->softirqs_enabled) {
2901 * We have done an ON -> OFF transition:
2903 curr->softirqs_enabled = 0;
2904 curr->softirq_disable_ip = ip;
2905 curr->softirq_disable_event = ++curr->irq_events;
2906 debug_atomic_inc(softirqs_off_events);
2908 * Whoops, we wanted softirqs off, so why aren't they?
2910 DEBUG_LOCKS_WARN_ON(!softirq_count());
2912 debug_atomic_inc(redundant_softirqs_off);
2915 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2918 * If non-trylock use in a hardirq or softirq context, then
2919 * mark the lock as used in these contexts:
2921 if (!hlock->trylock) {
2923 if (curr->hardirq_context)
2924 if (!mark_lock(curr, hlock,
2925 LOCK_USED_IN_HARDIRQ_READ))
2927 if (curr->softirq_context)
2928 if (!mark_lock(curr, hlock,
2929 LOCK_USED_IN_SOFTIRQ_READ))
2932 if (curr->hardirq_context)
2933 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2935 if (curr->softirq_context)
2936 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2940 if (!hlock->hardirqs_off) {
2942 if (!mark_lock(curr, hlock,
2943 LOCK_ENABLED_HARDIRQ_READ))
2945 if (curr->softirqs_enabled)
2946 if (!mark_lock(curr, hlock,
2947 LOCK_ENABLED_SOFTIRQ_READ))
2950 if (!mark_lock(curr, hlock,
2951 LOCK_ENABLED_HARDIRQ))
2953 if (curr->softirqs_enabled)
2954 if (!mark_lock(curr, hlock,
2955 LOCK_ENABLED_SOFTIRQ))
2963 static inline unsigned int task_irq_context(struct task_struct *task)
2965 return 2 * !!task->hardirq_context + !!task->softirq_context;
2968 static int separate_irq_context(struct task_struct *curr,
2969 struct held_lock *hlock)
2971 unsigned int depth = curr->lockdep_depth;
2974 * Keep track of points where we cross into an interrupt context:
2977 struct held_lock *prev_hlock;
2979 prev_hlock = curr->held_locks + depth-1;
2981 * If we cross into another context, reset the
2982 * hash key (this also prevents the checking and the
2983 * adding of the dependency to 'prev'):
2985 if (prev_hlock->irq_context != hlock->irq_context)
2991 #else /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
2994 int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2995 enum lock_usage_bit new_bit)
2997 WARN_ON(1); /* Impossible innit? when we don't have TRACE_IRQFLAG */
3001 static inline int mark_irqflags(struct task_struct *curr,
3002 struct held_lock *hlock)
3007 static inline unsigned int task_irq_context(struct task_struct *task)
3012 static inline int separate_irq_context(struct task_struct *curr,
3013 struct held_lock *hlock)
3018 #endif /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
3021 * Mark a lock with a usage bit, and validate the state transition:
3023 static int mark_lock(struct task_struct *curr, struct held_lock *this,
3024 enum lock_usage_bit new_bit)
3026 unsigned int new_mask = 1 << new_bit, ret = 1;
3029 * If already set then do not dirty the cacheline,
3030 * nor do any checks:
3032 if (likely(hlock_class(this)->usage_mask & new_mask))
3038 * Make sure we didn't race:
3040 if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
3045 hlock_class(this)->usage_mask |= new_mask;
3047 if (!save_trace(hlock_class(this)->usage_traces + new_bit))
3051 #define LOCKDEP_STATE(__STATE) \
3052 case LOCK_USED_IN_##__STATE: \
3053 case LOCK_USED_IN_##__STATE##_READ: \
3054 case LOCK_ENABLED_##__STATE: \
3055 case LOCK_ENABLED_##__STATE##_READ:
3056 #include "lockdep_states.h"
3057 #undef LOCKDEP_STATE
3058 ret = mark_lock_irq(curr, this, new_bit);
3063 debug_atomic_dec(nr_unused_locks);
3066 if (!debug_locks_off_graph_unlock())
3075 * We must printk outside of the graph_lock:
3078 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
3080 print_irqtrace_events(curr);
3088 * Initialize a lock instance's lock-class mapping info:
3090 void lockdep_init_map(struct lockdep_map *lock, const char *name,
3091 struct lock_class_key *key, int subclass)
3095 for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
3096 lock->class_cache[i] = NULL;
3098 #ifdef CONFIG_LOCK_STAT
3099 lock->cpu = raw_smp_processor_id();
3103 * Can't be having no nameless bastards around this place!
3105 if (DEBUG_LOCKS_WARN_ON(!name)) {
3106 lock->name = "NULL";
3113 * No key, no joy, we need to hash something.
3115 if (DEBUG_LOCKS_WARN_ON(!key))
3118 * Sanity check, the lock-class key must be persistent:
3120 if (!static_obj(key)) {
3121 printk("BUG: key %px not in .data!\n", key);
3123 * What it says above ^^^^^, I suggest you read it.
3125 DEBUG_LOCKS_WARN_ON(1);
3130 if (unlikely(!debug_locks))
3134 unsigned long flags;
3136 if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion))
3139 raw_local_irq_save(flags);
3140 current->lockdep_recursion = 1;
3141 register_lock_class(lock, subclass, 1);
3142 current->lockdep_recursion = 0;
3143 raw_local_irq_restore(flags);
3146 EXPORT_SYMBOL_GPL(lockdep_init_map);
3148 struct lock_class_key __lockdep_no_validate__;
3149 EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
3152 print_lock_nested_lock_not_held(struct task_struct *curr,
3153 struct held_lock *hlock,
3156 if (!debug_locks_off())
3158 if (debug_locks_silent)
3162 pr_warn("==================================\n");
3163 pr_warn("WARNING: Nested lock was not taken\n");
3164 print_kernel_ident();
3165 pr_warn("----------------------------------\n");
3167 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
3170 pr_warn("\nbut this task is not holding:\n");
3171 pr_warn("%s\n", hlock->nest_lock->name);
3173 pr_warn("\nstack backtrace:\n");
3176 pr_warn("\nother info that might help us debug this:\n");
3177 lockdep_print_held_locks(curr);
3179 pr_warn("\nstack backtrace:\n");
3185 static int __lock_is_held(const struct lockdep_map *lock, int read);
3188 * This gets called for every mutex_lock*()/spin_lock*() operation.
3189 * We maintain the dependency maps and validate the locking attempt:
3191 * The callers must make sure that IRQs are disabled before calling it,
3192 * otherwise we could get an interrupt which would want to take locks,
3193 * which would end up in lockdep again.
3195 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3196 int trylock, int read, int check, int hardirqs_off,
3197 struct lockdep_map *nest_lock, unsigned long ip,
3198 int references, int pin_count)
3200 struct task_struct *curr = current;
3201 struct lock_class *class = NULL;
3202 struct held_lock *hlock;
3208 if (unlikely(!debug_locks))
3211 if (!prove_locking || lock->key == &__lockdep_no_validate__)
3214 if (subclass < NR_LOCKDEP_CACHING_CLASSES)
3215 class = lock->class_cache[subclass];
3219 if (unlikely(!class)) {
3220 class = register_lock_class(lock, subclass, 0);
3225 debug_class_ops_inc(class);
3227 if (very_verbose(class)) {
3228 printk("\nacquire class [%px] %s", class->key, class->name);
3229 if (class->name_version > 1)
3230 printk(KERN_CONT "#%d", class->name_version);
3231 printk(KERN_CONT "\n");
3236 * Add the lock to the list of currently held locks.
3237 * (we dont increase the depth just yet, up until the
3238 * dependency checks are done)
3240 depth = curr->lockdep_depth;
3242 * Ran out of static storage for our per-task lock stack again have we?
3244 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
3247 class_idx = class - lock_classes + 1;
3250 hlock = curr->held_locks + depth - 1;
3251 if (hlock->class_idx == class_idx && nest_lock) {
3252 if (hlock->references) {
3254 * Check: unsigned int references:12, overflow.
3256 if (DEBUG_LOCKS_WARN_ON(hlock->references == (1 << 12)-1))
3259 hlock->references++;
3261 hlock->references = 2;
3268 hlock = curr->held_locks + depth;
3270 * Plain impossible, we just registered it and checked it weren't no
3271 * NULL like.. I bet this mushroom I ate was good!
3273 if (DEBUG_LOCKS_WARN_ON(!class))
3275 hlock->class_idx = class_idx;
3276 hlock->acquire_ip = ip;
3277 hlock->instance = lock;
3278 hlock->nest_lock = nest_lock;
3279 hlock->irq_context = task_irq_context(curr);
3280 hlock->trylock = trylock;
3282 hlock->check = check;
3283 hlock->hardirqs_off = !!hardirqs_off;
3284 hlock->references = references;
3285 #ifdef CONFIG_LOCK_STAT
3286 hlock->waittime_stamp = 0;
3287 hlock->holdtime_stamp = lockstat_clock();
3289 hlock->pin_count = pin_count;
3291 if (check && !mark_irqflags(curr, hlock))
3294 /* mark it as used: */
3295 if (!mark_lock(curr, hlock, LOCK_USED))
3299 * Calculate the chain hash: it's the combined hash of all the
3300 * lock keys along the dependency chain. We save the hash value
3301 * at every step so that we can get the current hash easily
3302 * after unlock. The chain hash is then used to cache dependency
3305 * The 'key ID' is what is the most compact key value to drive
3306 * the hash, not class->key.
3309 * Whoops, we did it again.. ran straight out of our static allocation.
3311 if (DEBUG_LOCKS_WARN_ON(class_idx > MAX_LOCKDEP_KEYS))
3314 chain_key = curr->curr_chain_key;
3317 * How can we have a chain hash when we ain't got no keys?!
3319 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
3324 hlock->prev_chain_key = chain_key;
3325 if (separate_irq_context(curr, hlock)) {
3329 chain_key = iterate_chain_key(chain_key, class_idx);
3331 if (nest_lock && !__lock_is_held(nest_lock, -1))
3332 return print_lock_nested_lock_not_held(curr, hlock, ip);
3334 if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
3337 curr->curr_chain_key = chain_key;
3338 curr->lockdep_depth++;
3339 check_chain_key(curr);
3340 #ifdef CONFIG_DEBUG_LOCKDEP
3341 if (unlikely(!debug_locks))
3344 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
3346 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
3347 printk(KERN_DEBUG "depth: %i max: %lu!\n",
3348 curr->lockdep_depth, MAX_LOCK_DEPTH);
3350 lockdep_print_held_locks(current);
3351 debug_show_all_locks();
3357 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
3358 max_lockdep_depth = curr->lockdep_depth;
3364 print_unlock_imbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
3367 if (!debug_locks_off())
3369 if (debug_locks_silent)
3373 pr_warn("=====================================\n");
3374 pr_warn("WARNING: bad unlock balance detected!\n");
3375 print_kernel_ident();
3376 pr_warn("-------------------------------------\n");
3377 pr_warn("%s/%d is trying to release lock (",
3378 curr->comm, task_pid_nr(curr));
3379 print_lockdep_cache(lock);
3382 pr_warn("but there are no more locks to release!\n");
3383 pr_warn("\nother info that might help us debug this:\n");
3384 lockdep_print_held_locks(curr);
3386 pr_warn("\nstack backtrace:\n");
3392 static int match_held_lock(const struct held_lock *hlock,
3393 const struct lockdep_map *lock)
3395 if (hlock->instance == lock)
3398 if (hlock->references) {
3399 const struct lock_class *class = lock->class_cache[0];
3402 class = look_up_lock_class(lock, 0);
3405 * If look_up_lock_class() failed to find a class, we're trying
3406 * to test if we hold a lock that has never yet been acquired.
3407 * Clearly if the lock hasn't been acquired _ever_, we're not
3408 * holding it either, so report failure.
3414 * References, but not a lock we're actually ref-counting?
3415 * State got messed up, follow the sites that change ->references
3416 * and try to make sense of it.
3418 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
3421 if (hlock->class_idx == class - lock_classes + 1)
3428 /* @depth must not be zero */
3429 static struct held_lock *find_held_lock(struct task_struct *curr,
3430 struct lockdep_map *lock,
3431 unsigned int depth, int *idx)
3433 struct held_lock *ret, *hlock, *prev_hlock;
3437 hlock = curr->held_locks + i;
3439 if (match_held_lock(hlock, lock))
3443 for (i--, prev_hlock = hlock--;
3445 i--, prev_hlock = hlock--) {
3447 * We must not cross into another context:
3449 if (prev_hlock->irq_context != hlock->irq_context) {
3453 if (match_held_lock(hlock, lock)) {
3464 static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
3467 struct held_lock *hlock;
3469 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
3472 for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
3473 if (!__lock_acquire(hlock->instance,
3474 hlock_class(hlock)->subclass,
3476 hlock->read, hlock->check,
3477 hlock->hardirqs_off,
3478 hlock->nest_lock, hlock->acquire_ip,
3479 hlock->references, hlock->pin_count))
3486 __lock_set_class(struct lockdep_map *lock, const char *name,
3487 struct lock_class_key *key, unsigned int subclass,
3490 struct task_struct *curr = current;
3491 struct held_lock *hlock;
3492 struct lock_class *class;
3496 if (unlikely(!debug_locks))
3499 depth = curr->lockdep_depth;
3501 * This function is about (re)setting the class of a held lock,
3502 * yet we're not actually holding any locks. Naughty user!
3504 if (DEBUG_LOCKS_WARN_ON(!depth))
3507 hlock = find_held_lock(curr, lock, depth, &i);
3509 return print_unlock_imbalance_bug(curr, lock, ip);
3511 lockdep_init_map(lock, name, key, 0);
3512 class = register_lock_class(lock, subclass, 0);
3513 hlock->class_idx = class - lock_classes + 1;
3515 curr->lockdep_depth = i;
3516 curr->curr_chain_key = hlock->prev_chain_key;
3518 if (reacquire_held_locks(curr, depth, i))
3522 * I took it apart and put it back together again, except now I have
3523 * these 'spare' parts.. where shall I put them.
3525 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
3530 static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
3532 struct task_struct *curr = current;
3533 struct held_lock *hlock;
3537 if (unlikely(!debug_locks))
3540 depth = curr->lockdep_depth;
3542 * This function is about (re)setting the class of a held lock,
3543 * yet we're not actually holding any locks. Naughty user!
3545 if (DEBUG_LOCKS_WARN_ON(!depth))
3548 hlock = find_held_lock(curr, lock, depth, &i);
3550 return print_unlock_imbalance_bug(curr, lock, ip);
3552 curr->lockdep_depth = i;
3553 curr->curr_chain_key = hlock->prev_chain_key;
3555 WARN(hlock->read, "downgrading a read lock");
3557 hlock->acquire_ip = ip;
3559 if (reacquire_held_locks(curr, depth, i))
3563 * I took it apart and put it back together again, except now I have
3564 * these 'spare' parts.. where shall I put them.
3566 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
3572 * Remove the lock to the list of currently held locks - this gets
3573 * called on mutex_unlock()/spin_unlock*() (or on a failed
3574 * mutex_lock_interruptible()).
3576 * @nested is an hysterical artifact, needs a tree wide cleanup.
3579 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
3581 struct task_struct *curr = current;
3582 struct held_lock *hlock;
3586 if (unlikely(!debug_locks))
3589 depth = curr->lockdep_depth;
3591 * So we're all set to release this lock.. wait what lock? We don't
3592 * own any locks, you've been drinking again?
3594 if (DEBUG_LOCKS_WARN_ON(depth <= 0))
3595 return print_unlock_imbalance_bug(curr, lock, ip);
3598 * Check whether the lock exists in the current stack
3601 hlock = find_held_lock(curr, lock, depth, &i);
3603 return print_unlock_imbalance_bug(curr, lock, ip);
3605 if (hlock->instance == lock)
3606 lock_release_holdtime(hlock);
3608 WARN(hlock->pin_count, "releasing a pinned lock\n");
3610 if (hlock->references) {
3611 hlock->references--;
3612 if (hlock->references) {
3614 * We had, and after removing one, still have
3615 * references, the current lock stack is still
3616 * valid. We're done!
3623 * We have the right lock to unlock, 'hlock' points to it.
3624 * Now we remove it from the stack, and add back the other
3625 * entries (if any), recalculating the hash along the way:
3628 curr->lockdep_depth = i;
3629 curr->curr_chain_key = hlock->prev_chain_key;
3632 * The most likely case is when the unlock is on the innermost
3633 * lock. In this case, we are done!
3638 if (reacquire_held_locks(curr, depth, i + 1))
3642 * We had N bottles of beer on the wall, we drank one, but now
3643 * there's not N-1 bottles of beer left on the wall...
3645 DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth-1);
3648 * Since reacquire_held_locks() would have called check_chain_key()
3649 * indirectly via __lock_acquire(), we don't need to do it again
3655 static int __lock_is_held(const struct lockdep_map *lock, int read)
3657 struct task_struct *curr = current;
3660 for (i = 0; i < curr->lockdep_depth; i++) {
3661 struct held_lock *hlock = curr->held_locks + i;
3663 if (match_held_lock(hlock, lock)) {
3664 if (read == -1 || hlock->read == read)
3674 static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
3676 struct pin_cookie cookie = NIL_COOKIE;
3677 struct task_struct *curr = current;
3680 if (unlikely(!debug_locks))
3683 for (i = 0; i < curr->lockdep_depth; i++) {
3684 struct held_lock *hlock = curr->held_locks + i;
3686 if (match_held_lock(hlock, lock)) {
3688 * Grab 16bits of randomness; this is sufficient to not
3689 * be guessable and still allows some pin nesting in
3690 * our u32 pin_count.
3692 cookie.val = 1 + (prandom_u32() >> 16);
3693 hlock->pin_count += cookie.val;
3698 WARN(1, "pinning an unheld lock\n");
3702 static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
3704 struct task_struct *curr = current;
3707 if (unlikely(!debug_locks))
3710 for (i = 0; i < curr->lockdep_depth; i++) {
3711 struct held_lock *hlock = curr->held_locks + i;
3713 if (match_held_lock(hlock, lock)) {
3714 hlock->pin_count += cookie.val;
3719 WARN(1, "pinning an unheld lock\n");
3722 static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
3724 struct task_struct *curr = current;
3727 if (unlikely(!debug_locks))
3730 for (i = 0; i < curr->lockdep_depth; i++) {
3731 struct held_lock *hlock = curr->held_locks + i;
3733 if (match_held_lock(hlock, lock)) {
3734 if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
3737 hlock->pin_count -= cookie.val;
3739 if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
3740 hlock->pin_count = 0;
3746 WARN(1, "unpinning an unheld lock\n");
3750 * Check whether we follow the irq-flags state precisely:
3752 static void check_flags(unsigned long flags)
3754 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
3755 defined(CONFIG_TRACE_IRQFLAGS)
3759 if (irqs_disabled_flags(flags)) {
3760 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
3761 printk("possible reason: unannotated irqs-off.\n");
3764 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
3765 printk("possible reason: unannotated irqs-on.\n");
3770 * We dont accurately track softirq state in e.g.
3771 * hardirq contexts (such as on 4KSTACKS), so only
3772 * check if not in hardirq contexts:
3774 if (!hardirq_count()) {
3775 if (softirq_count()) {
3776 /* like the above, but with softirqs */
3777 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
3779 /* lick the above, does it taste good? */
3780 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
3785 print_irqtrace_events(current);
3789 void lock_set_class(struct lockdep_map *lock, const char *name,
3790 struct lock_class_key *key, unsigned int subclass,
3793 unsigned long flags;
3795 if (unlikely(current->lockdep_recursion))
3798 raw_local_irq_save(flags);
3799 current->lockdep_recursion = 1;
3801 if (__lock_set_class(lock, name, key, subclass, ip))
3802 check_chain_key(current);
3803 current->lockdep_recursion = 0;
3804 raw_local_irq_restore(flags);
3806 EXPORT_SYMBOL_GPL(lock_set_class);
3808 void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
3810 unsigned long flags;
3812 if (unlikely(current->lockdep_recursion))
3815 raw_local_irq_save(flags);
3816 current->lockdep_recursion = 1;
3818 if (__lock_downgrade(lock, ip))
3819 check_chain_key(current);
3820 current->lockdep_recursion = 0;
3821 raw_local_irq_restore(flags);
3823 EXPORT_SYMBOL_GPL(lock_downgrade);
3826 * We are not always called with irqs disabled - do that here,
3827 * and also avoid lockdep recursion:
3829 void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3830 int trylock, int read, int check,
3831 struct lockdep_map *nest_lock, unsigned long ip)
3833 unsigned long flags;
3835 if (unlikely(current->lockdep_recursion))
3838 raw_local_irq_save(flags);
3841 current->lockdep_recursion = 1;
3842 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3843 __lock_acquire(lock, subclass, trylock, read, check,
3844 irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
3845 current->lockdep_recursion = 0;
3846 raw_local_irq_restore(flags);
3848 EXPORT_SYMBOL_GPL(lock_acquire);
3850 void lock_release(struct lockdep_map *lock, int nested,
3853 unsigned long flags;
3855 if (unlikely(current->lockdep_recursion))
3858 raw_local_irq_save(flags);
3860 current->lockdep_recursion = 1;
3861 trace_lock_release(lock, ip);
3862 if (__lock_release(lock, nested, ip))
3863 check_chain_key(current);
3864 current->lockdep_recursion = 0;
3865 raw_local_irq_restore(flags);
3867 EXPORT_SYMBOL_GPL(lock_release);
3869 int lock_is_held_type(const struct lockdep_map *lock, int read)
3871 unsigned long flags;
3874 if (unlikely(current->lockdep_recursion))
3875 return 1; /* avoid false negative lockdep_assert_held() */
3877 raw_local_irq_save(flags);
3880 current->lockdep_recursion = 1;
3881 ret = __lock_is_held(lock, read);
3882 current->lockdep_recursion = 0;
3883 raw_local_irq_restore(flags);
3887 EXPORT_SYMBOL_GPL(lock_is_held_type);
3889 struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
3891 struct pin_cookie cookie = NIL_COOKIE;
3892 unsigned long flags;
3894 if (unlikely(current->lockdep_recursion))
3897 raw_local_irq_save(flags);
3900 current->lockdep_recursion = 1;
3901 cookie = __lock_pin_lock(lock);
3902 current->lockdep_recursion = 0;
3903 raw_local_irq_restore(flags);
3907 EXPORT_SYMBOL_GPL(lock_pin_lock);
3909 void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
3911 unsigned long flags;
3913 if (unlikely(current->lockdep_recursion))
3916 raw_local_irq_save(flags);
3919 current->lockdep_recursion = 1;
3920 __lock_repin_lock(lock, cookie);
3921 current->lockdep_recursion = 0;
3922 raw_local_irq_restore(flags);
3924 EXPORT_SYMBOL_GPL(lock_repin_lock);
3926 void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
3928 unsigned long flags;
3930 if (unlikely(current->lockdep_recursion))
3933 raw_local_irq_save(flags);
3936 current->lockdep_recursion = 1;
3937 __lock_unpin_lock(lock, cookie);
3938 current->lockdep_recursion = 0;
3939 raw_local_irq_restore(flags);
3941 EXPORT_SYMBOL_GPL(lock_unpin_lock);
3943 #ifdef CONFIG_LOCK_STAT
3945 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3948 if (!debug_locks_off())
3950 if (debug_locks_silent)
3954 pr_warn("=================================\n");
3955 pr_warn("WARNING: bad contention detected!\n");
3956 print_kernel_ident();
3957 pr_warn("---------------------------------\n");
3958 pr_warn("%s/%d is trying to contend lock (",
3959 curr->comm, task_pid_nr(curr));
3960 print_lockdep_cache(lock);
3963 pr_warn("but there are no locks held!\n");
3964 pr_warn("\nother info that might help us debug this:\n");
3965 lockdep_print_held_locks(curr);
3967 pr_warn("\nstack backtrace:\n");
3974 __lock_contended(struct lockdep_map *lock, unsigned long ip)
3976 struct task_struct *curr = current;
3977 struct held_lock *hlock;
3978 struct lock_class_stats *stats;
3980 int i, contention_point, contending_point;
3982 depth = curr->lockdep_depth;
3984 * Whee, we contended on this lock, except it seems we're not
3985 * actually trying to acquire anything much at all..
3987 if (DEBUG_LOCKS_WARN_ON(!depth))
3990 hlock = find_held_lock(curr, lock, depth, &i);
3992 print_lock_contention_bug(curr, lock, ip);
3996 if (hlock->instance != lock)
3999 hlock->waittime_stamp = lockstat_clock();
4001 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
4002 contending_point = lock_point(hlock_class(hlock)->contending_point,
4005 stats = get_lock_stats(hlock_class(hlock));
4006 if (contention_point < LOCKSTAT_POINTS)
4007 stats->contention_point[contention_point]++;
4008 if (contending_point < LOCKSTAT_POINTS)
4009 stats->contending_point[contending_point]++;
4010 if (lock->cpu != smp_processor_id())
4011 stats->bounces[bounce_contended + !!hlock->read]++;
4015 __lock_acquired(struct lockdep_map *lock, unsigned long ip)
4017 struct task_struct *curr = current;
4018 struct held_lock *hlock;
4019 struct lock_class_stats *stats;
4021 u64 now, waittime = 0;
4024 depth = curr->lockdep_depth;
4026 * Yay, we acquired ownership of this lock we didn't try to
4027 * acquire, how the heck did that happen?
4029 if (DEBUG_LOCKS_WARN_ON(!depth))
4032 hlock = find_held_lock(curr, lock, depth, &i);
4034 print_lock_contention_bug(curr, lock, _RET_IP_);
4038 if (hlock->instance != lock)
4041 cpu = smp_processor_id();
4042 if (hlock->waittime_stamp) {
4043 now = lockstat_clock();
4044 waittime = now - hlock->waittime_stamp;
4045 hlock->holdtime_stamp = now;
4048 trace_lock_acquired(lock, ip);
4050 stats = get_lock_stats(hlock_class(hlock));
4053 lock_time_inc(&stats->read_waittime, waittime);
4055 lock_time_inc(&stats->write_waittime, waittime);
4057 if (lock->cpu != cpu)
4058 stats->bounces[bounce_acquired + !!hlock->read]++;
4064 void lock_contended(struct lockdep_map *lock, unsigned long ip)
4066 unsigned long flags;
4068 if (unlikely(!lock_stat || !debug_locks))
4071 if (unlikely(current->lockdep_recursion))
4074 raw_local_irq_save(flags);
4076 current->lockdep_recursion = 1;
4077 trace_lock_contended(lock, ip);
4078 __lock_contended(lock, ip);
4079 current->lockdep_recursion = 0;
4080 raw_local_irq_restore(flags);
4082 EXPORT_SYMBOL_GPL(lock_contended);
4084 void lock_acquired(struct lockdep_map *lock, unsigned long ip)
4086 unsigned long flags;
4088 if (unlikely(!lock_stat || !debug_locks))
4091 if (unlikely(current->lockdep_recursion))
4094 raw_local_irq_save(flags);
4096 current->lockdep_recursion = 1;
4097 __lock_acquired(lock, ip);
4098 current->lockdep_recursion = 0;
4099 raw_local_irq_restore(flags);
4101 EXPORT_SYMBOL_GPL(lock_acquired);
4105 * Used by the testsuite, sanitize the validator state
4106 * after a simulated failure:
4109 void lockdep_reset(void)
4111 unsigned long flags;
4114 raw_local_irq_save(flags);
4115 current->curr_chain_key = 0;
4116 current->lockdep_depth = 0;
4117 current->lockdep_recursion = 0;
4118 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
4119 nr_hardirq_chains = 0;
4120 nr_softirq_chains = 0;
4121 nr_process_chains = 0;
4123 for (i = 0; i < CHAINHASH_SIZE; i++)
4124 INIT_HLIST_HEAD(chainhash_table + i);
4125 raw_local_irq_restore(flags);
4129 * Remove all references to a lock class. The caller must hold the graph lock.
4131 static void zap_class(struct lock_class *class)
4133 struct lock_list *entry;
4137 * Remove all dependencies this lock is
4140 for (i = 0, entry = list_entries; i < nr_list_entries; i++, entry++) {
4141 if (entry->class != class && entry->links_to != class)
4143 list_del_rcu(&entry->entry);
4144 /* Clear .class and .links_to to avoid double removal. */
4145 WRITE_ONCE(entry->class, NULL);
4146 WRITE_ONCE(entry->links_to, NULL);
4149 * Unhash the class and remove it from the all_lock_classes list:
4151 hlist_del_rcu(&class->hash_entry);
4152 list_del(&class->lock_entry);
4154 RCU_INIT_POINTER(class->key, NULL);
4155 RCU_INIT_POINTER(class->name, NULL);
4158 static inline int within(const void *addr, void *start, unsigned long size)
4160 return addr >= start && addr < start + size;
4163 static void __lockdep_free_key_range(void *start, unsigned long size)
4165 struct lock_class *class;
4166 struct hlist_head *head;
4169 /* Unhash all classes that were created by a module. */
4170 for (i = 0; i < CLASSHASH_SIZE; i++) {
4171 head = classhash_table + i;
4172 hlist_for_each_entry_rcu(class, head, hash_entry) {
4173 if (!within(class->key, start, size) &&
4174 !within(class->name, start, size))
4182 * Used in module.c to remove lock classes from memory that is going to be
4183 * freed; and possibly re-used by other modules.
4185 * We will have had one sync_sched() before getting here, so we're guaranteed
4186 * nobody will look up these exact classes -- they're properly dead but still
4189 void lockdep_free_key_range(void *start, unsigned long size)
4191 unsigned long flags;
4194 init_data_structures_once();
4196 raw_local_irq_save(flags);
4197 locked = graph_lock();
4198 __lockdep_free_key_range(start, size);
4201 raw_local_irq_restore(flags);
4204 * Wait for any possible iterators from look_up_lock_class() to pass
4205 * before continuing to free the memory they refer to.
4207 * sync_sched() is sufficient because the read-side is IRQ disable.
4212 * XXX at this point we could return the resources to the pool;
4213 * instead we leak them. We would need to change to bitmap allocators
4214 * instead of the linear allocators we have now.
4219 * Check whether any element of the @lock->class_cache[] array refers to a
4220 * registered lock class. The caller must hold either the graph lock or the
4223 static bool lock_class_cache_is_registered(struct lockdep_map *lock)
4225 struct lock_class *class;
4226 struct hlist_head *head;
4229 for (i = 0; i < CLASSHASH_SIZE; i++) {
4230 head = classhash_table + i;
4231 hlist_for_each_entry_rcu(class, head, hash_entry) {
4232 for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
4233 if (lock->class_cache[j] == class)
4240 /* The caller must hold the graph lock. Does not sleep. */
4241 static void __lockdep_reset_lock(struct lockdep_map *lock)
4243 struct lock_class *class;
4247 * Remove all classes this lock might have:
4249 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
4251 * If the class exists we look it up and zap it:
4253 class = look_up_lock_class(lock, j);
4258 * Debug check: in the end all mapped classes should
4261 if (WARN_ON_ONCE(lock_class_cache_is_registered(lock)))
4265 void lockdep_reset_lock(struct lockdep_map *lock)
4267 unsigned long flags;
4270 init_data_structures_once();
4272 raw_local_irq_save(flags);
4273 locked = graph_lock();
4274 __lockdep_reset_lock(lock);
4277 raw_local_irq_restore(flags);
4280 void __init lockdep_init(void)
4282 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
4284 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
4285 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
4286 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
4287 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
4288 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
4289 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
4290 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
4292 printk(" memory used by lock dependency info: %zu kB\n",
4293 (sizeof(lock_classes) +
4294 sizeof(classhash_table) +
4295 sizeof(list_entries) +
4296 sizeof(chainhash_table)
4297 #ifdef CONFIG_PROVE_LOCKING
4299 + sizeof(lock_chains)
4300 + sizeof(chain_hlocks)
4305 printk(" per task-struct memory footprint: %zu bytes\n",
4306 sizeof(((struct task_struct *)NULL)->held_locks));
4310 print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
4311 const void *mem_to, struct held_lock *hlock)
4313 if (!debug_locks_off())
4315 if (debug_locks_silent)
4319 pr_warn("=========================\n");
4320 pr_warn("WARNING: held lock freed!\n");
4321 print_kernel_ident();
4322 pr_warn("-------------------------\n");
4323 pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n",
4324 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
4326 lockdep_print_held_locks(curr);
4328 pr_warn("\nstack backtrace:\n");
4332 static inline int not_in_range(const void* mem_from, unsigned long mem_len,
4333 const void* lock_from, unsigned long lock_len)
4335 return lock_from + lock_len <= mem_from ||
4336 mem_from + mem_len <= lock_from;
4340 * Called when kernel memory is freed (or unmapped), or if a lock
4341 * is destroyed or reinitialized - this code checks whether there is
4342 * any held lock in the memory range of <from> to <to>:
4344 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
4346 struct task_struct *curr = current;
4347 struct held_lock *hlock;
4348 unsigned long flags;
4351 if (unlikely(!debug_locks))
4354 raw_local_irq_save(flags);
4355 for (i = 0; i < curr->lockdep_depth; i++) {
4356 hlock = curr->held_locks + i;
4358 if (not_in_range(mem_from, mem_len, hlock->instance,
4359 sizeof(*hlock->instance)))
4362 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
4365 raw_local_irq_restore(flags);
4367 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
4369 static void print_held_locks_bug(void)
4371 if (!debug_locks_off())
4373 if (debug_locks_silent)
4377 pr_warn("====================================\n");
4378 pr_warn("WARNING: %s/%d still has locks held!\n",
4379 current->comm, task_pid_nr(current));
4380 print_kernel_ident();
4381 pr_warn("------------------------------------\n");
4382 lockdep_print_held_locks(current);
4383 pr_warn("\nstack backtrace:\n");
4387 void debug_check_no_locks_held(void)
4389 if (unlikely(current->lockdep_depth > 0))
4390 print_held_locks_bug();
4392 EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
4395 void debug_show_all_locks(void)
4397 struct task_struct *g, *p;
4399 if (unlikely(!debug_locks)) {
4400 pr_warn("INFO: lockdep is turned off.\n");
4403 pr_warn("\nShowing all locks held in the system:\n");
4406 for_each_process_thread(g, p) {
4407 if (!p->lockdep_depth)
4409 lockdep_print_held_locks(p);
4410 touch_nmi_watchdog();
4411 touch_all_softlockup_watchdogs();
4416 pr_warn("=============================================\n\n");
4418 EXPORT_SYMBOL_GPL(debug_show_all_locks);
4422 * Careful: only use this function if you are sure that
4423 * the task cannot run in parallel!
4425 void debug_show_held_locks(struct task_struct *task)
4427 if (unlikely(!debug_locks)) {
4428 printk("INFO: lockdep is turned off.\n");
4431 lockdep_print_held_locks(task);
4433 EXPORT_SYMBOL_GPL(debug_show_held_locks);
4435 asmlinkage __visible void lockdep_sys_exit(void)
4437 struct task_struct *curr = current;
4439 if (unlikely(curr->lockdep_depth)) {
4440 if (!debug_locks_off())
4443 pr_warn("================================================\n");
4444 pr_warn("WARNING: lock held when returning to user space!\n");
4445 print_kernel_ident();
4446 pr_warn("------------------------------------------------\n");
4447 pr_warn("%s/%d is leaving the kernel with locks still held!\n",
4448 curr->comm, curr->pid);
4449 lockdep_print_held_locks(curr);
4453 * The lock history for each syscall should be independent. So wipe the
4454 * slate clean on return to userspace.
4456 lockdep_invariant_state(false);
4459 void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
4461 struct task_struct *curr = current;
4463 /* Note: the following can be executed concurrently, so be careful. */
4465 pr_warn("=============================\n");
4466 pr_warn("WARNING: suspicious RCU usage\n");
4467 print_kernel_ident();
4468 pr_warn("-----------------------------\n");
4469 pr_warn("%s:%d %s!\n", file, line, s);
4470 pr_warn("\nother info that might help us debug this:\n\n");
4471 pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
4472 !rcu_lockdep_current_cpu_online()
4473 ? "RCU used illegally from offline CPU!\n"
4474 : !rcu_is_watching()
4475 ? "RCU used illegally from idle CPU!\n"
4477 rcu_scheduler_active, debug_locks);
4480 * If a CPU is in the RCU-free window in idle (ie: in the section
4481 * between rcu_idle_enter() and rcu_idle_exit(), then RCU
4482 * considers that CPU to be in an "extended quiescent state",
4483 * which means that RCU will be completely ignoring that CPU.
4484 * Therefore, rcu_read_lock() and friends have absolutely no
4485 * effect on a CPU running in that state. In other words, even if
4486 * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
4487 * delete data structures out from under it. RCU really has no
4488 * choice here: we need to keep an RCU-free window in idle where
4489 * the CPU may possibly enter into low power mode. This way we can
4490 * notice an extended quiescent state to other CPUs that started a grace
4491 * period. Otherwise we would delay any grace period as long as we run
4494 * So complain bitterly if someone does call rcu_read_lock(),
4495 * rcu_read_lock_bh() and so on from extended quiescent states.
4497 if (!rcu_is_watching())
4498 pr_warn("RCU used illegally from extended quiescent state!\n");
4500 lockdep_print_held_locks(curr);
4501 pr_warn("\nstack backtrace:\n");
4504 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);