diff options
Diffstat (limited to 'kernel/locking')
| -rw-r--r-- | kernel/locking/lockdep.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 74d084a398be..6ff1e8405a83 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -2768,8 +2768,18 @@ static int check_irq_usage(struct task_struct *curr, struct held_lock *prev, * Step 3: we found a bad match! Now retrieve a lock from the backward * list whose usage mask matches the exclusive usage mask from the * lock found on the forward list. + * + * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering + * the follow case: + * + * When trying to add A -> B to the graph, we find that there is a + * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M, + * that B -> ... -> M. However M is **softirq-safe**, if we use exact + * invert bits of M's usage_mask, we will find another lock N that is + * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not + * cause a inversion deadlock. */ - backward_mask = original_mask(target_entry1->class->usage_mask); + backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL); ret = find_usage_backwards(&this, backward_mask, &target_entry); if (bfs_error(ret)) { |