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

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Message-ID: <20080308102321.4527372e@bree.surriel.com>
Date:	Sat, 8 Mar 2008 10:23:21 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Davide Libenzi <davidel@...ilserver.org>
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 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.

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