Messages in this thread Patch in this message | | | From | j.glisse@gmail ... | Subject | [PATCH] locking/lockdep: Fix expected depth value in __lock_release() | Date | Mon, 19 Oct 2015 15:30:28 -0400 |
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From: Jérôme Glisse <jglisse@redhat.com>
In __lock_release() we are removing one entry from the stack and rebuilding the hash chain by re-adding entry above the entry we just removed. If the entry removed was between 2 entry of same class then this 2 entry might be coalesced into one single entry which in turns means that the lockdep_depth value will not be incremented and thus the expected lockdep_depth value after this operation will be wrong triggering an unjustified WARN_ONCE() at the end of __lock_release().
This patch adjust the expect depth value by decrementing it if what was previously 2 entry inside the stack are coalesced into only one entry.
Note that __lock_set_class() does not suffer from same issue as it adds a new class and thus can not lead to coalescing of stack entry.
Signed-off-by: Jérôme Glisse <jglisse@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sasha Levin <sasha.levin@oracle.com> --- kernel/locking/lockdep.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 4e49cc4..cac5e21 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3428,6 +3428,8 @@ found_it: curr->curr_chain_key = hlock->prev_chain_key; for (i++; i < depth; i++) { + int tmp = curr->lockdep_depth; + hlock = curr->held_locks + i; if (!__lock_acquire(hlock->instance, hlock_class(hlock)->subclass, hlock->trylock, @@ -3435,6 +3437,13 @@ found_it: hlock->nest_lock, hlock->acquire_ip, hlock->references, hlock->pin_count)) return 0; + /* + * If nest_lock is true and the lock we just removed allow two + * lock of same class to be consolidated in only one held_lock + * then the lockdep_depth count will not increase as we expect + * it to. So adjust the expected depth value accordingly. + */ + depth -= (curr->lockdep_depth == tmp); } /* -- 1.8.3.1
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