linux-kernel - Possible locking issue in viotape.c

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Date:	Thu, 06 Dec 2007 21:29:58 -0400
From:	Kevin Winchester <kjwinchester@...il.com>
To:	Daniel Walker <dwalker@...sta.com>
CC:	Ingo Molnar <mingo@...e.hu>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux@...mer.net,
	jonathan@...masters.org, matthias.kaehlcke@...il.com
Subject: Possible locking issue in viotape.c

Daniel Walker wrote:
> 
> I've posted all the ones I've done so far ..
> 
> ftp://source.mvista.com/pub/dwalker/sem2mutex-2.6.24-rc4/
> 
> Feel free to review or test them.. I've found it pretty easy to simply
> grep for certain class of semaphore usage, check if it's conforming to
> the mutex requirements, then convert it or not.. Checking them is
> getting to be a habit, so I don't think a list would help me.. However,
> someone else might be able to use it..
> 

Thanks, that helps me not duplicate anything.  One of the first ones I
was looking at (before your post) was viotape.c, which is in your patch
set.  However, looking at the uses of the semaphore, I see that on line
409-410 the following code:

        if (noblock)
                return count;

which seems to ignore the fact that the semaphore has been downed (not
to mention the dma buffer and op struct allocations.  I think it should be:

	if (noblock)
		ret = count;
		goto free_dma;

instead.  Do you want to make sure I'm right about that and fold it into
your patch?  Or have you already submitted your patch (or should it be
in a separate patch?  Alternatively, I can submit the patch if you don't
want to bother with it.

-- 
Kevin Winchester
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