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Message-ID: <tip-a63b03e2d2477586440741677ecac45bcf28d7b1@git.kernel.org>
Date: Fri, 9 Jan 2015 04:34:37 -0800
From: tip-bot for Chris Wilson <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: hpa@...or.com, dave@...olabs.net, linux-kernel@...r.kernel.org,
torvalds@...ux-foundation.org, peterz@...radead.org,
chris@...is-wilson.co.uk, daniel.vetter@...ll.ch, mingo@...nel.org,
tglx@...utronix.de
Subject: [tip:locking/urgent] mutex:
Always clear owner field upon mutex_unlock()
Commit-ID: a63b03e2d2477586440741677ecac45bcf28d7b1
Gitweb: http://git.kernel.org/tip/a63b03e2d2477586440741677ecac45bcf28d7b1
Author: Chris Wilson <chris@...is-wilson.co.uk>
AuthorDate: Tue, 6 Jan 2015 10:29:35 +0000
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 9 Jan 2015 11:20:39 +0100
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@...is-wilson.co.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Davidlohr Bueso <dave@...olabs.net>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Linus Torvalds <torvalds@...ux-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@...nel.org>
---
kernel/locking/mutex-debug.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
index 5cf6731..3ef3736 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);
}
--
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