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.2.00.1006091041540.4506@i5.linux-foundation.org>
Date:	Wed, 9 Jun 2010 10:43:33 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	tytso@....edu
cc:	Ingo Molnar <mingo@...e.hu>, Salman <sqazi@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	peterz@...radead.org, akpm@...x-foundation.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	tytso@...gle.com, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] Fix a race in pid generation that causes pids to be
 reused immediately.



On Wed, 9 Jun 2010, tytso@....edu wrote:
> 
> Well, I was thinking about something like this:

No, this is wrong for the case where you end up having to allocate a new 
pidmap and/or overflow max_pid.

It also doesn't set the bit at all.

> There appears to be some interesting uses of the bitmap by
> find_ge_pid() and next_pidmap() that I haven't completely grokked yet,

We need that bitmap to handle the overflow max_pid case. We are _not_ 
returning just increasing pid numbers.

		Linus
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