From: Andi Kleen <andi@firstfloor.org>
To: Salman <sqazi@google.com>
Cc: peterz@infradead.org, mingo@elte.hu, akpm@inux-foundation.org,
linux-kernel@vger.kernel.org, tytso@google.com
Subject: Re: [PATCH] Fix a race in pid generation that causes pids to be reused immediately.
Date: Wed, 09 Jun 2010 08:53:31 +0200 [thread overview]
Message-ID: <87d3w066j8.fsf@basil.nowhere.org> (raw)
In-Reply-To: <20100609062438.29081.91635.stgit@bumblebee1.mtv.corp.google.com> (Salman's message of "Tue\, 08 Jun 2010 23\:24\:38 -0700")
Salman <sqazi@google.com> writes:
> +++ b/kernel/pid.c
> @@ -153,8 +153,17 @@ static int alloc_pidmap(struct pid_namespace *pid_ns)
> if (likely(atomic_read(&map->nr_free))) {
> do {
> if (!test_and_set_bit(offset, map->page)) {
> + int prev;
> atomic_dec(&map->nr_free);
> - pid_ns->last_pid = pid;
> +
> + do {
> + prev = last;
> + last = cmpxchg(&pid_ns->last_pid,
> + prev,
> + pid);
At some point not all architectures in Linux supported cmpxchg,
so it was not allowed to use it unconditionally in portable code.
This might have changed now (at least the UP only architectures fall
back to a generic cmpxchg now I think), but I'm not sure you have full
coverage on SMP.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2010-06-09 6:53 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-09 6:24 [PATCH] Fix a race in pid generation that causes pids to be reused immediately Salman
2010-06-09 6:53 ` Andi Kleen [this message]
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
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
-- strict thread matches above, loose matches on Subject: below --
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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