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Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull lockdep fix from Thomas Gleixner:
 "A single fix for the stack trace caching logic in lockdep, where the
  duplicate avoidance managed to store no back trace at all"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/lockdep: Fix stack trace caching logic
This commit is contained in:
Linus Torvalds 2016-02-14 12:02:05 -08:00
commit cb490d632b
1 changed files with 10 additions and 6 deletions
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16
kernel/locking/lockdep.c
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@ -1822,7 +1822,7 @@ check_deadlock(struct task_struct *curr, struct held_lock *next,
*/
static int
check_prev_add(struct task_struct *curr, struct held_lock *prev,
struct held_lock *next, int distance, int trylock_loop)
struct held_lock *next, int distance, int *stack_saved)
{
struct lock_list *entry;
int ret;
@ -1883,8 +1883,11 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
}
}
if (!trylock_loop && !save_trace(&trace))
return 0;
if (!*stack_saved) {
if (!save_trace(&trace))
return 0;
*stack_saved = 1;
}
/*
* Ok, all validations passed, add the new lock
@ -1907,6 +1910,8 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
* Debugging printouts:
*/
if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
/* We drop graph lock, so another thread can overwrite trace. */
*stack_saved = 0;
graph_unlock();
printk("\n new dependency: ");
print_lock_name(hlock_class(prev));
@ -1929,7 +1934,7 @@ static int
check_prevs_add(struct task_struct *curr, struct held_lock *next)
{
int depth = curr->lockdep_depth;
int trylock_loop = 0;
int stack_saved = 0;
struct held_lock *hlock;
/*
@ -1956,7 +1961,7 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
*/
if (hlock->read != 2 && hlock->check) {
if (!check_prev_add(curr, hlock, next,
distance, trylock_loop))
distance, &stack_saved))
return 0;
/*
* Stop after the first non-trylock entry,
@ -1979,7 +1984,6 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
if (curr->held_locks[depth].irq_context !=
curr->held_locks[depth-1].irq_context)
break;
trylock_loop = 1;
}
return 1;
out_bug: