From: Linus Torvalds <torvalds@linux-foundation.org>
To: tytso@mit.edu
Cc: Ingo Molnar <mingo@elte.hu>, Salman <sqazi@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
peterz@infradead.org, akpm@inux-foundation.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
tytso@google.com, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] Fix a race in pid generation that causes pids to be reused immediately.
Date: Wed, 9 Jun 2010 10:25:50 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.2.00.1006091023341.4506@i5.linux-foundation.org> (raw)
In-Reply-To: <alpine.LFD.2.00.1006091013340.4506@i5.linux-foundation.org>
On Wed, 9 Jun 2010, Linus Torvalds wrote:
>
> Otherwise you have three threads, two of which pick the same pid (because
> the test-and-set isn't atomic), and a third of which picks a new one.
In fact, I don't think you need three threads at all. It's perfectly ok to
just have two threads, and they'd both end up picking the same 'pid'
without the atomicity guarantees of that 'test_and_set()' bitmap access.
And they'd both be perfectly fine setting last_pid to that (shared) pid if
I read that cmpxchg loop right. No?
Linus
next prev parent reply other threads:[~2010-06-09 17:26 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-09 6:24 Salman
2010-06-09 6:53 ` Andi Kleen
2010-06-09 9:48 ` Ingo Molnar
2010-06-09 15:39 ` Linus Torvalds
2010-06-09 15:50 ` tytso
2010-06-09 16:06 ` Linus Torvalds
2010-06-09 17:10 ` tytso
2010-06-09 17:23 ` Linus Torvalds
2010-06-09 17:25 ` Linus Torvalds [this message]
2010-06-09 17:34 ` tytso
2010-06-09 17:43 ` Linus Torvalds
2010-06-09 17:47 ` tytso
2010-06-09 18:09 ` Salman Qazi
2010-06-09 11:49 ` Michel Lespinasse
2010-06-09 12:37 ` tytso
2010-06-09 12:17 ` tytso
2010-06-09 21:00 Salman
2010-06-09 21:21 ` Linus Torvalds
2010-06-09 21:33 ` Peter Zijlstra
2010-06-09 22:20 ` Linus Torvalds
2010-06-09 22:27 ` Linus Torvalds
2010-06-10 0:08 ` Salman Qazi
2010-06-10 0:20 ` Linus Torvalds
[not found] ` <AANLkTilXJ0X2qxD9cNTlLayKzySEZu1HEZUWu--Go8kw@mail.gmail.com>
2010-06-10 5:55 ` Salman Qazi
2010-06-10 16:39 ` Linus Torvalds
2010-06-10 20:09 Salman
2010-06-10 20:38 ` tytso
2010-06-10 21:04 ` Salman Qazi
2010-06-10 21:24 Salman
2010-06-11 17:17 Salman
2010-06-11 17:44 ` Linus Torvalds
2010-06-11 22:49 ` Salman
2010-06-11 23:07 ` Linus Torvalds
2010-06-14 23:58 ` Andrew Morton
2010-06-15 0:56 ` tytso
2010-06-15 1:55 ` Andrew Morton
2010-06-15 3:26 ` Paul Mackerras
2010-06-15 4:21 ` Andrew Morton
2010-06-15 4:38 ` Eric Dumazet
2010-06-15 6:57 ` Benjamin Herrenschmidt
2010-06-15 7:25 ` Paul Mackerras
2010-06-15 12:56 ` tytso
2010-06-15 13:06 ` Kyle McMartin
2010-06-15 14:35 ` Peter Zijlstra
2010-06-15 19:37 ` Andrew Morton
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