From: Andrew Morton <akpm@linux-foundation.org>
To: Paul Mackerras <paulus@samba.org>
Cc: tytso@mit.edu, Salman <sqazi@google.com>,
mingo@elte.hu, linux-kernel@vger.kernel.org,
peterz@infradead.org, tytso@google.com,
torvalds@linux-foundation.org, walken@google.com,
Chen Liqin <liqin.chen@sunplusct.com>,
Lennox Wu <lennox.wu@gmail.com>
Subject: Re: [PATCH] Fix a race in pid generation that causes pids to be reused immediately.
Date: Mon, 14 Jun 2010 21:21:50 -0700 [thread overview]
Message-ID: <20100614212150.4dcb1feb.akpm@linux-foundation.org> (raw)
In-Reply-To: <20100615032608.GB30479@drongo>
On Tue, 15 Jun 2010 13:26:08 +1000 Paul Mackerras <paulus@samba.org> wrote:
> On Mon, Jun 14, 2010 at 06:55:56PM -0700, Andrew Morton wrote:
>
> > > kernel/sched_clock.c: if (cmpxchg64(&scd->clock, old_clock, clock) != old_cloc
> >
> > I guess that'll flush out any stragglers.
>
> And break most non-x86 32-bit architectures, including 32-bit powerpc.
If CONFIG_SMP=y, yes. On UP there's a generic implementation
(include/asm-generic/cmpxchg-local.h, include/asm-generic/cmpxchg.h)
> Fortunately that code is only used if CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
> is set, and it looks like only x86 and ia64 set it.
>
If that happens then the best fix is for those architectures to get
themselves a cmpxchg64(). Unless for some reason it's simply
unimplementable? Worst case I guess one could use a global spinlock.
Second-worst-case: hashed spinlocks.
next prev parent reply other threads:[~2010-06-15 4:23 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-11 17:17 [PATCH] Fix a race in pid generation that causes pids to be reused immediately 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 [this message]
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
2010-06-15 18:35 ` [PATCH 0/1] (Was: Fix a race in pid generation that causes pids to be reused immediately.) Oleg Nesterov
2010-06-15 18:35 ` [PATCH 1/1] pids: alloc_pidmap: remove the unnecessary boundary checks Oleg Nesterov
-- strict thread matches above, loose matches on Subject: below --
2010-06-10 21:24 [PATCH] Fix a race in pid generation that causes pids to be reused immediately Salman
2010-06-10 20:09 Salman
2010-06-10 20:38 ` tytso
2010-06-10 21:04 ` Salman Qazi
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
2010-06-09 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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