lkml.org 
[lkml]   [2011]   [Sep]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH v3] 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>
    Acked-by: Tejun Heo <tj@kernel.org>
    Cc: stable@kernel.org
    ---
    kernel/workqueue.c | 7 ++++++-
    1 files changed, 6 insertions(+), 1 deletions(-)

    diff --git a/kernel/workqueue.c b/kernel/workqueue.c
    index 25fb1b0..1783aab 100644
    --- a/kernel/workqueue.c
    +++ b/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 ||
    --
    1.7.3.1

    ----- End forwarded message -----

    \
     
     \ /
      Last update: 2011-09-11 05:43    [W:0.020 / U:60.372 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site