From 6f008e72cd111a119b5d8de8c5438d892aae99eb Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 12 Mar 2014 13:24:42 +0100 Subject: locking/mutex: Fix debug checks OK, so commit: 1d8fe7dc8078 ("locking/mutexes: Unlock the mutex without the wait_lock") generates this boot warning when CONFIG_DEBUG_MUTEXES=y: WARNING: CPU: 0 PID: 139 at /usr/src/linux-2.6/kernel/locking/mutex-debug.c:82 debug_mutex_unlock+0x155/0x180() DEBUG_LOCKS_WARN_ON(lock->owner != current) And that makes sense, because as soon as we release the lock a new owner can come in... One would think that !__mutex_slowpath_needs_to_unlock() implementations suffer the same, but for DEBUG we fall back to mutex-null.h which has an unconditional 1 for that. The mutex debug code requires the mutex to be unlocked after doing the debug checks, otherwise it can find inconsistent state. Reported-by: Ingo Molnar Signed-off-by: Peter Zijlstra Cc: jason.low2@hp.com Link: http://lkml.kernel.org/r/20140312122442.GB27965@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- kernel/locking/mutex.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'kernel/locking/mutex.c') diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 02c61a9..14fe72c 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -34,6 +34,13 @@ #ifdef CONFIG_DEBUG_MUTEXES # include "mutex-debug.h" # include +/* + * Must be 0 for the debug case so we do not do the unlock outside of the + * wait_lock region. debug_mutex_unlock() will do the actual unlock in this + * case. + */ +# undef __mutex_slowpath_needs_to_unlock +# define __mutex_slowpath_needs_to_unlock() 0 #else # include "mutex.h" # include -- cgit v1.1