locking/lockdep: Define INITIAL_CHAIN_KEY for chain keys to start with

Chain keys are computed using Jenkins hash function, which needs an initial
hash to start with. Dedicate a macro to make this clear and configurable. A
later patch changes this initial chain key.

Signed-off-by: Yuyang Du <duyuyang@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bvanassche@acm.org
Cc: frederic@kernel.org
Cc: ming.lei@redhat.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190506081939.74287-9-duyuyang@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 5d05b81..d4e6959 100644 (file)
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -229,6 +229,7 @@ struct lock_chain {
  * bitfield and hitting the BUG in hlock_class().
  */
 #define MAX_LOCKDEP_KEYS               ((1UL << MAX_LOCKDEP_KEYS_BITS) - 1)
+#define INITIAL_CHAIN_KEY              0
 
 struct held_lock {
        /*

diff --git a/init/init_task.c b/init/init_task.c
index 1b15cb9..afa6ad7 100644 (file)
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -167,7 +167,7 @@ struct task_struct init_task
 #endif
 #ifdef CONFIG_LOCKDEP
        .lockdep_depth = 0, /* no locks held yet */
-       .curr_chain_key = 0,
+       .curr_chain_key = INITIAL_CHAIN_KEY,
        .lockdep_recursion = 0,
 #endif
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index b7d9c28..9edf6f1 100644 (file)
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -362,7 +362,7 @@ static inline u64 iterate_chain_key(u64 key, u32 idx)
 void lockdep_init_task(struct task_struct *task)
 {
        task->lockdep_depth = 0; /* no locks held yet */
-       task->curr_chain_key = 0;
+       task->curr_chain_key = INITIAL_CHAIN_KEY;
        task->lockdep_recursion = 0;
 }
 
@@ -857,7 +857,7 @@ static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
 static bool check_lock_chain_key(struct lock_chain *chain)
 {
 #ifdef CONFIG_PROVE_LOCKING
-       u64 chain_key = 0;
+       u64 chain_key = INITIAL_CHAIN_KEY;
        int i;
 
        for (i = chain->base; i < chain->base + chain->depth; i++)
@@ -2524,7 +2524,7 @@ static void
 print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
 {
        struct held_lock *hlock;
-       u64 chain_key = 0;
+       u64 chain_key = INITIAL_CHAIN_KEY;
        int depth = curr->lockdep_depth;
        int i = get_first_held_lock(curr, hlock_next);
 
@@ -2544,7 +2544,7 @@ print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_ne
 static void print_chain_keys_chain(struct lock_chain *chain)
 {
        int i;
-       u64 chain_key = 0;
+       u64 chain_key = INITIAL_CHAIN_KEY;
        int class_id;
 
        printk("depth: %u\n", chain->depth);
@@ -2848,7 +2848,7 @@ static void check_chain_key(struct task_struct *curr)
 #ifdef CONFIG_DEBUG_LOCKDEP
        struct held_lock *hlock, *prev_hlock = NULL;
        unsigned int i;
-       u64 chain_key = 0;
+       u64 chain_key = INITIAL_CHAIN_KEY;
 
        for (i = 0; i < curr->lockdep_depth; i++) {
                hlock = curr->held_locks + i;
@@ -2872,7 +2872,7 @@ static void check_chain_key(struct task_struct *curr)
 
                if (prev_hlock && (prev_hlock->irq_context !=
                                                        hlock->irq_context))
-                       chain_key = 0;
+                       chain_key = INITIAL_CHAIN_KEY;
                chain_key = iterate_chain_key(chain_key, hlock->class_idx);
                prev_hlock = hlock;
        }
@@ -3787,14 +3787,14 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
                /*
                 * How can we have a chain hash when we ain't got no keys?!
                 */
-               if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
+               if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
                        return 0;
                chain_head = 1;
        }
 
        hlock->prev_chain_key = chain_key;
        if (separate_irq_context(curr, hlock)) {
-               chain_key = 0;
+               chain_key = INITIAL_CHAIN_KEY;
                chain_head = 1;
        }
        chain_key = iterate_chain_key(chain_key, class_idx);
@@ -4636,7 +4636,7 @@ static void remove_class_from_lock_chain(struct pending_free *pf,
        return;
 
 recalc:
-       chain_key = 0;
+       chain_key = INITIAL_CHAIN_KEY;
        for (i = chain->base; i < chain->base + chain->depth; i++)
                chain_key = iterate_chain_key(chain_key, chain_hlocks[i] + 1);
        if (chain->depth && chain->chain_key == chain_key)