locking/mutex: Fix debug checks
OK, so commit:
1d8fe7dc80
("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 <mingo@kernel.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: jason.low2@hp.com
Link: http://lkml.kernel.org/r/20140312122442.GB27965@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
parent
34c6bc2c91
commit
6f008e72cd
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@ -83,6 +83,12 @@ void debug_mutex_unlock(struct mutex *lock)
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DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next);
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DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next);
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mutex_clear_owner(lock);
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mutex_clear_owner(lock);
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/*
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* __mutex_slowpath_needs_to_unlock() is explicitly 0 for debug
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* mutexes so that we can do it here after we've verified state.
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*/
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atomic_set(&lock->count, 1);
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}
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}
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void debug_mutex_init(struct mutex *lock, const char *name,
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void debug_mutex_init(struct mutex *lock, const char *name,
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@ -34,6 +34,13 @@
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#ifdef CONFIG_DEBUG_MUTEXES
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#ifdef CONFIG_DEBUG_MUTEXES
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# include "mutex-debug.h"
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# include "mutex-debug.h"
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# include <asm-generic/mutex-null.h>
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# include <asm-generic/mutex-null.h>
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/*
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* Must be 0 for the debug case so we do not do the unlock outside of the
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* wait_lock region. debug_mutex_unlock() will do the actual unlock in this
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* case.
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*/
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# undef __mutex_slowpath_needs_to_unlock
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# define __mutex_slowpath_needs_to_unlock() 0
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#else
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#else
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# include "mutex.h"
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# include "mutex.h"
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# include <asm/mutex.h>
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# include <asm/mutex.h>
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