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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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