linux-kernel - Re: [PATCH 04/10] workqueue: destroy worker directly in the idle timeout handler

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Date:	Wed, 7 May 2014 23:30:35 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 04/10] workqueue: destroy worker directly in the idle
 timeout handler

On Wed, May 7, 2014 at 9:41 PM, Tejun Heo <tj@...nel.org> wrote:
> On Wed, May 07, 2014 at 09:38:39PM +0800, Lai Jiangshan wrote:
>> On Wed, May 7, 2014 at 9:12 PM, Tejun Heo <tj@...nel.org> wrote:
>> > Hello, Lai.
>> >
>> > On Wed, May 07, 2014 at 03:10:20PM +0800, Lai Jiangshan wrote:
>> >> 1) complete() can't be called inside attach_mutex due to the worker
>> >>    shouldn't access to the pool after complete().
>> >
>> > Sure, complete it after releasing the lock.  Shutdown can't complete
>> > before the completion gets completed, right?
>> >
>> >> 2) put_unbound_pool() may called from get_unbound_pool(), we need to add
>> >>    an additional check and avoid the wait_for_completion() if so.
>>
>> Do you accept if I remove put_unbound_pool() from get_unbound_pool()
>> and use several freeing code instead?
>
> Hah?  How much extra complexity are we talking about?  It's a single
> if, no?

        DECLARE_COMPLETION_ONSTACK(completion);
#1

        ...

        while ((worker = first_worker(pool))) {
                destroy_worker(worker);
                pool->detach_completion = &completion;
#2
        }

        ...
        unlock;

        if (pool->detach_completion)
                wait_for_completion();
#3

One thing is separated into 3 places and about 5~7lines.
I hope a single wait_for_completion() or single wait_event().


get_unbound_pool():
fail:
    if (pool)
        put_unbound_pool(pool);

I think we can change it into:

fail:
    if (pool) {
        if (pool->id >= 0)
            idr_remove(&worker_pool_idr, pool->id);
        call_rcu_sched(&pool->rcu, rcu_free_pool);
    }

Thanks,
Lai

>
> --
> tejun
> --
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