The patch titled
workqueue: lock cwq access in drain_workqueue
has been added to the -mm tree. Its filename is
workqueue-lock-cwq-access-in-drain_workqueue.patch
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------------------------------------------------------
Subject: workqueue: lock cwq access in drain_workqueue
From: Thomas Tuttle <ttuttle@xxxxxxxxxxxx>
Take cwq->gcwq->lock to avoid racing between drain_workqueue checking to
make sure the workqueues are empty and cwq_dec_nr_in_flight decrementing
and then incrementing nr_active when it activates a delayed work.
We discovered this when a corner case in one of our drivers resulted in us
trying to destroy a workqueue in which the remaining work would always
requeue itself again in the same workqueue. We would hit this race
condition and trip the BUG_ON on workqueue.c:3080.
Signed-off-by: Thomas Tuttle <ttuttle@xxxxxxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/workqueue.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff -puN kernel/workqueue.c~workqueue-lock-cwq-access-in-drain_workqueue kernel/workqueue.c
--- a/kernel/workqueue.c~workqueue-lock-cwq-access-in-drain_workqueue
+++ a/kernel/workqueue.c
@@ -2412,8 +2412,13 @@ reflush:
for_each_cwq_cpu(cpu, wq) {
struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq);
+ bool drained;
- if (!cwq->nr_active && list_empty(&cwq->delayed_works))
+ spin_lock_irq(&cwq->gcwq->lock);
+ drained = !cwq->nr_active && list_empty(&cwq->delayed_works);
+ spin_unlock_irq(&cwq->gcwq->lock);
+
+ if (drained)
continue;
if (++flush_cnt == 10 ||
_
Patches currently in -mm which might be from ttuttle@xxxxxxxxxxxx are
workqueue-lock-cwq-access-in-drain_workqueue.patch
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