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locking/mutex: Initialize mutex_waiter::ww_ctx with poison when debugging

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Help catch cases where mutex_lock is used directly on w/w mutexes, which
otherwise result in the w/w tasks reading uninitialized data.

Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-12-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Nicolai Hähnle 2016-12-21 19:46:39 +01:00 committed by Ingo Molnar
parent c516df978d
commit 977625a693
2 changed files with 5 additions and 0 deletions
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1
include/linux/poison.h
View File

@ -80,6 +80,7 @@
/********** kernel/mutexes **********/
#define MUTEX_DEBUG_INIT 0x11
#define MUTEX_DEBUG_FREE 0x22
#define MUTEX_POISON_WW_CTX ((void *) 0x500 + POISON_POINTER_DELTA)
/********** lib/flex_array.c **********/
#define FLEX_ARRAY_FREE 0x6c /* for use-after-free poisoning */

4
kernel/locking/mutex.c
View File

@ -785,6 +785,10 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
if (!use_ww_ctx) {
/* add waiting tasks to the end of the waitqueue (FIFO): */
list_add_tail(&waiter.list, &lock->wait_list);
#ifdef CONFIG_DEBUG_MUTEXES
waiter.ww_ctx = MUTEX_POISON_WW_CTX;
#endif
} else {
/* Add in stamp order, waking up waiters that must back off. */
ret = __ww_mutex_add_waiter(&waiter, lock, ww_ctx);