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SubjectRe: [PATCH] workqueue: fix spurious CPU locality WARN from process_one_work()
On Sun, Jul 22, 2012 at 09:43:27AM -0700, Tejun Heo wrote:
> 25511a4776 "workqueue: reimplement CPU online rebinding to handle idle
> workers" added CPU locality sanity check in process_one_work(). It
> triggers if a worker is executing on a different CPU without UNBOUND
> or REBIND set.
>
> This works for all normal workers but rescuers can trigger this
> spuriously when they're serving the unbound or a disassociated
> global_cwq - rescuers don't have either flag set and thus its
> gcwq->cpu can be a different value including %WORK_CPU_UNBOUND.
>
> Fix it by additionally testing %GCWQ_DISASSOCIATED.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Reported-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> LKML-Refence: <20120721213656.GA7783@linux.vnet.ibm.com>
> ---
> This should fix it. Will queue it on wq/for-3.6.

I am running my tests on it, will let you know how it goes.

Thanx, Paul

> Thanks!
>
> kernel/workqueue.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -1949,7 +1949,13 @@ __acquires(&gcwq->lock)
>
> lockdep_copy_map(&lockdep_map, &work->lockdep_map);
> #endif
> + /*
> + * Ensure we're on the correct CPU. DISASSOCIATED test is
> + * necessary to avoid spurious warnings from rescuers servicing the
> + * unbound or a disassociated gcwq.
> + */
> WARN_ON_ONCE(!(worker->flags & (WORKER_UNBOUND | WORKER_REBIND)) &&
> + !(gcwq->flags & GCWQ_DISASSOCIATED) &&
> raw_smp_processor_id() != gcwq->cpu);
>
> /*
>



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