linux-kernel - Re: [PATCH] eventfd signal race in aio

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Message-ID: <20080308113744.J1091@desktop>
Date:	Sat, 8 Mar 2008 11:38:27 -1000 (HST)
From:	Jeff Roberson <jroberson@...sapeake.net>
To:	Davide Libenzi <davidel@...ilserver.org>
cc:	Rik van Riel <riel@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Zach Brown <zach.brown@...cle.com>
Subject: Re: [PATCH] eventfd signal race in aio_complete()

On Sat, 8 Mar 2008, Davide Libenzi wrote:

> On Sat, 8 Mar 2008, Rik van Riel wrote:
>
>> On Fri, 7 Mar 2008 20:29:20 -0800 (PST)
>> Davide Libenzi <davidel@...ilserver.org> wrote:
>>
>>> The second solution/patch simply moves the eventfd_signal() call before
>>> the __aio_put_req() call, but after the event has beed "ringed".
>>> We should be clear to go with the shorter/nicer second solution. Those
>>> patches builds, but I'm not even signing them off till I tested them.
>>
>> If there are no spinlock ordering issues between &ctx->ctx_lock
>> and &ctx->wqh.lock (taken inside eventfd_signal), then the second
>> patch is indeed preferable.
>>
>> Jeff and I did look at that briefly last night, but were not
>> familiar enough with the code to decide whether or not that was
>> safe.
>
> There's no interlocking between the two, so let's go with #2.
> Jeff, would you mind giving patch #2 a spin in your test suite?

I agree #2 would be best as well.  It may take me a few days due to some 
equipment issues but I will get back to you as soon as I can.

Thanks,
Jeff

>
>
>
> - Davide
>
>
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