linux-kernel - Re: [PATCH] Fix a race in pid generation that causes pids to be reused immediately.

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Message-ID: <alpine.LFD.2.00.1006091525250.4506@i5.linux-foundation.org>
Date:	Wed, 9 Jun 2010 15:27:37 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Salman <sqazi@...gle.com>, akpm@...ux-foundation.org,
	mingo@...e.hu, linux-kernel@...r.kernel.org, tytso@...gle.com
Subject: Re: [PATCH] Fix a race in pid generation that causes pids to be
 reused immediately.



On Wed, 9 Jun 2010, Linus Torvalds wrote:
> 
> Quite possibly. I'd worry about the overflow case a bit, but it's 
> certainly going to get the right value when base << MAX_INT.

Having given it a couple of seconds more thought, I don't think there is 
an overflow case either. All of a/b/base are guaranteed to be non-negative 
(or our pid code is in worse trouble anyway), so there is no overflow 
possible. So yes. Just comparing a-base < b-base should always be safe.

			Linus


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