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| author | Chris Wilson <chris@chris-wilson.co.uk> | 2015-01-06 10:29:35 +0000 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-01-09 11:20:39 +0100 |
| commit | a63b03e2d2477586440741677ecac45bcf28d7b1 (patch) | |
| tree | e59245ca27e14ca56dfb59ac351d6666ee8c3050 | |
| parent | 11c8f01b423b2d9742ce21e44cb7da7b55429ad5 (diff) | |
| download | lwn-a63b03e2d2477586440741677ecac45bcf28d7b1.tar.gz lwn-a63b03e2d2477586440741677ecac45bcf28d7b1.zip | |
mutex: Always clear owner field upon mutex_unlock()
Currently if DEBUG_MUTEXES is enabled, the mutex->owner field is only
cleared iff debug_locks is active. This exposes a race to other users of
the field where the mutex->owner may be still set to a stale value,
potentially upsetting mutex_spin_on_owner() among others.
References: https://bugs.freedesktop.org/show_bug.cgi?id=87955
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1420540175-30204-1-git-send-email-chris@chris-wilson.co.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | kernel/locking/mutex-debug.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c index 5cf6731b98e9..3ef3736002d8 100644 --- a/kernel/locking/mutex-debug.c +++ b/kernel/locking/mutex-debug.c @@ -80,13 +80,13 @@ void debug_mutex_unlock(struct mutex *lock) DEBUG_LOCKS_WARN_ON(lock->owner != current); DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next); - mutex_clear_owner(lock); } /* * __mutex_slowpath_needs_to_unlock() is explicitly 0 for debug * mutexes so that we can do it here after we've verified state. */ + mutex_clear_owner(lock); atomic_set(&lock->count, 1); } |