Message-ID: <4C4712B4.9040706@kernel.org>
Date: Wed, 21 Jul 2010 17:31:00 +0200
From: Tejun Heo <tj@kernel.org>
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To: David Howells <dhowells@redhat.com>
CC: Arjan van de Ven <arjan@linux.intel.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        torvalds@linux-foundation.org, mingo@elte.hu,
        linux-kernel@vger.kernel.org, jeff@garzik.org,
        akpm@linux-foundation.org, rusty@rustcorp.com.au,
        cl@linux-foundation.org, oleg@redhat.com, axboe@kernel.dk,
        dwalker@codeaurora.org, stefanr@s5r6.in-berlin.de, florian@mickler.org,
        andi@firstfloor.org, mst@redhat.com, randy.dunlap@oracle.com,
        Arjan van de Ven <arjan@infradead.org>
Subject: Re: [PATCHSET] workqueue: implement and use WQ_UNBOUND
References: <4C470B46.4040604@kernel.org> <7b6bba36-5330-4e27-b7a9-3a4113b6b379@email.android.com> <21485.1279717725@redhat.com> <15189.1279725944@redhat.com>
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Hello,

On 07/21/2010 05:25 PM, David Howells wrote:
>> Each gcwq keeps track of currently running works in a hash table and looks
>> whether the work in question is already executing before starting executing
>> it.  It's a bit complex but as a work_struct may be freed once execution
>> starts, the status needs to be tracked outside.
> 
> Thanks, that's what I wanted to know.
> 
> I presume this survives an executing work_struct being freed, reallocated and
> requeued before the address of the work_struct is removed from the hash table?

It will unnecessarily stall the execution of the new work if the last
work is still running but nothing will be broken correctness-wise.

> I can see at least one way of doing this: marking the work_struct address in
> the hash when the address becomes pending again so that the process of hash
> removal will cause the work_struct to be requeued automatically.

If I'm correctly understanding what you're saying, the code already
does about the same thing.

Thanks.

-- 
tejun
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