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    SubjectRe: [PATCH v2 3/6] workqueue: change value of lcpu in __queue_delayed_work_on()
    On Wed, Aug 15, 2012 at 03:10:13AM +0900, Joonsoo Kim wrote:
    > We assign cpu id into work struct's data field in __queue_delayed_work_on().
    > In current implementation, when work is come in first time,
    > current running cpu id is assigned.
    > If we do __queue_delayed_work_on() with CPU A on CPU B,
    > __queue_work() invoked in delayed_work_timer_fn() go into
    > the following sub-optimal path in case of WQ_NON_REENTRANT.
    >
    > gcwq = get_gcwq(cpu);
    > if (wq->flags & WQ_NON_REENTRANT &&
    > (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {
    >
    > Change lcpu to @cpu and rechange lcpu to local cpu if lcpu is WORK_CPU_UNBOUND.
    > It is sufficient to prevent to go into sub-optimal path.
    >
    > Signed-off-by: Joonsoo Kim <js1304@gmail.com>
    >
    > diff --git a/kernel/workqueue.c b/kernel/workqueue.c
    > index 6a17ab0..f55ac26 100644
    > --- a/kernel/workqueue.c
    > +++ b/kernel/workqueue.c
    > @@ -1358,9 +1358,10 @@ static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
    > if (!(wq->flags & WQ_UNBOUND)) {
    > struct global_cwq *gcwq = get_work_gcwq(work);
    >
    > - if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
    > + lcpu = cpu;
    > + if (gcwq)
    > lcpu = gcwq->cpu;
    > - else
    > + if (lcpu == WORK_CPU_UNBOUND)
    > lcpu = raw_smp_processor_id();

    Can you please add a comment explanining what's going on?

    --
    tejun


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