diff options
| author | Tejun Heo <tj@kernel.org> | 2012-08-03 10:30:45 -0700 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2012-08-03 10:30:45 -0700 |
| commit | 959d1af8cffc8fd38ed53e8be1cf4ab8782f9c00 (patch) | |
| tree | 04ca9a7c88fe42f21fa4a6a209a2c16236615f45 /kernel/workqueue.c | |
| parent | d4283e9378619c14dc3826a6b0527eb5d967ffde (diff) | |
| download | lwn-959d1af8cffc8fd38ed53e8be1cf4ab8782f9c00.tar.gz lwn-959d1af8cffc8fd38ed53e8be1cf4ab8782f9c00.zip | |
workqueue: add missing smp_wmb() in process_one_work()
WORK_STRUCT_PENDING is used to claim ownership of a work item and
process_one_work() releases it before starting execution. When
someone else grabs PENDING, all pre-release updates to the work item
should be visible and all updates made by the new owner should happen
afterwards.
Grabbing PENDING uses test_and_set_bit() and thus has a full barrier;
however, clearing doesn't have a matching wmb. Given the preceding
spin_unlock and use of clear_bit, I don't believe this can be a
problem on an actual machine and there hasn't been any related report
but it still is theretically possible for clear_pending to permeate
upwards and happen before work->entry update.
Add an explicit smp_wmb() before work_clear_pending().
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: stable@vger.kernel.org
Diffstat (limited to 'kernel/workqueue.c')
| -rw-r--r-- | kernel/workqueue.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 70f95ab28f3d..5c26d36146b7 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1997,7 +1997,9 @@ __acquires(&gcwq->lock) spin_unlock_irq(&gcwq->lock); + smp_wmb(); /* paired with test_and_set_bit(PENDING) */ work_clear_pending(work); + lock_map_acquire_read(&cwq->wq->lockdep_map); lock_map_acquire(&lockdep_map); trace_workqueue_execute_start(work); |