From: Linus Torvalds <torvalds@linux-foundation.org>
To: Salman Qazi <sqazi@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
akpm@linux-foundation.org, mingo@elte.hu,
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, 9 Jun 2010 17:20:21 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.2.00.1006091719100.4506@i5.linux-foundation.org> (raw)
In-Reply-To: <AANLkTim56xHJM-6ZgFvEO2YetDLCnjaCoOtxYGTqtE0c@mail.gmail.com>
On Wed, 9 Jun 2010, Salman Qazi wrote:
>
> I don't think this gives the right answer in the a < base < b case.
> Here a - base < 0 and
> b - base > 0. But we really want b to be before a, since a has rolled
> over further than b.
Right you are.
> I think the right solution is comparing (a - base + max_pid) % max_pid
> with (b - base + max_pid) % max_pid. Am I correct or deluded? .
That would work, but it would be horrible. Just use the three compares
version: doing a integer 'mod' operator is _way_ more expensive.
Linus
next prev parent reply other threads:[~2010-06-10 0:20 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
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 [this message]
[not found] ` <AANLkTilXJ0X2qxD9cNTlLayKzySEZu1HEZUWu--Go8kw@mail.gmail.com>
2010-06-10 5:55 ` Salman Qazi
2010-06-10 16:39 ` Linus Torvalds
-- strict thread matches above, loose matches on Subject: below --
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
2010-06-10 21:24 Salman
2010-06-10 20:09 Salman
2010-06-10 20:38 ` tytso
2010-06-10 21:04 ` Salman Qazi
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
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
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