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

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Message-ID: <Pine.LNX.4.64.0803081236440.9905@alien.or.mcafeemobile.com>
Date:	Sat, 8 Mar 2008 12:38:00 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Rik van Riel <riel@...hat.com>
cc:	Jeff Roberson <jroberson@...sapeake.net>,
	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, 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?



- Davide


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