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SubjectRe: [PATCH 4/7 V6] workqueue: fix idle worker depletion
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On Sun, Sep 9, 2012 at 1:40 AM, Tejun Heo <tj@kernel.org> wrote:
> Hello, Lai.
>
> On Sun, Sep 09, 2012 at 01:12:53AM +0800, Lai Jiangshan wrote:
>> +/* does the manager need to be rebind after we just release gcwq->lock */
>> +static void maybe_rebind_manager(struct worker *manager)
>> +{
>> + struct global_cwq *gcwq = manager->pool->gcwq;
>> + bool assoc = !(gcwq->flags & GCWQ_DISASSOCIATED);
>> +
>> + if (assoc && (manager->flags & WORKER_UNBOUND)) {
>> + spin_unlock_irq(&gcwq->lock);
>> +
>> + if (worker_maybe_bind_and_lock(manager))
>> + worker_clr_flags(manager, WORKER_UNBOUND);
>> + }
>> +}
>
> We can reuse busy_worker_rebind_fn(), right?

busy_worker_rebind_fn() releases the gcwq->lock. we can't release the lock here.

>
>> pool->manager = worker;
>> + if (unlikely(!mutex_trylock(&pool->manager_mutex))) {
>> + /*
>> + * Ouch! rebind_workers() or gcwq_unbind_fn() beats we.
>> + * it can't return false here, otherwise it will lead to
>> + * worker depletion. So we release gcwq->lock and then
>> + * grab manager_mutex again.
>> + */
>> + spin_unlock_irq(&gcwq->lock);
>> + mutex_lock(&pool->manager_mutex);
>> + spin_lock_irq(&gcwq->lock);
>> +
>> + /* rebind_workers() can happen when we release gcwq->lock */
>> + maybe_rebind_manager(worker);
>
> And we can call process_scheduled_works() here and make the CPU
> hotplug check pool->manager and schedule rebind_work there.
>

sorry again. don't need.

Thanks.
Lai

>
> --
> tejun
> --
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