Messages in this thread Patch in this message | | | Date | Fri, 9 Sep 2011 19:00:53 -0400 | From | Thomas Tuttle <> | Subject | [PATCH v2] workqueue: lock cwq access in drain_workqueue |
| |
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@chromium.org> --- Updated to use bool instead of int (d'oh), and CCed maintainer.
kernel/workqueue.c | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 25fb1b0..0c2e585 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2412,8 +2412,14 @@ reflush: for_each_cwq_cpu(cpu, wq) { struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); + bool cwq_flushed; - if (!cwq->nr_active && list_empty(&cwq->delayed_works)) + spin_lock_irq(&cwq->gcwq->lock); + cwq_flushed = !cwq->nr_active + && list_empty(&cwq->delayed_works); + spin_unlock_irq(&cwq->gcwq->lock); + + if (cwq_flushed) continue; if (++flush_cnt == 10 || -- 1.7.3.1
| |