From: Andrew Morton <akpm@osdl.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: linas@austin.ibm.com, linux-kernel@vger.kernel.org,
Andrea Arcangeli <andrea@suse.de>
Subject: Re: PATCH: Race in 2.6.0-test2 timer code
Date: Tue, 29 Jul 2003 23:36:03 -0700 [thread overview]
Message-ID: <20030729233603.21ad2409.akpm@osdl.org> (raw)
In-Reply-To: <Pine.LNX.4.44.0307300733200.25010-100000@localhost.localdomain>
Ingo Molnar <mingo@elte.hu> wrote:
>
>
> On Tue, 29 Jul 2003, Andrew Morton wrote:
>
> > Andrea says that we need to take the per-timer lock in add_timer() and
> > del_timer(), but I haven't yet got around to working out why.
>
> this makes no sense - in 2.6 (and in 2.4) there's no safe add_timer() /
> del_timer() use without using external SMP synchronization. (There's one
> special timer use variant involving del_timer_sync() that was safe in 2.4
> but is unsafe in 2.6, see below.)
>
Well Andrea did mention a problem with the interval timers. But I am not
aware of the exact details of the race which he found, and I don't
understand why del_timer() and add_timer() would be needing the per-timer
locks.
You need to export __mod_timer to modules btw.
--- 25/kernel/ksyms.c~timer-race-fixes 2003-07-29 23:27:05.000000000 -0700
+++ 25-akpm/kernel/ksyms.c 2003-07-29 23:27:49.000000000 -0700
@@ -405,8 +405,6 @@ EXPORT_SYMBOL(proc_doulongvec_ms_jiffies
EXPORT_SYMBOL(proc_doulongvec_minmax);
/* interrupt handling */
-EXPORT_SYMBOL(add_timer);
-EXPORT_SYMBOL(del_timer);
EXPORT_SYMBOL(request_irq);
EXPORT_SYMBOL(free_irq);
@@ -433,7 +431,10 @@ EXPORT_SYMBOL(probe_irq_off);
#ifdef CONFIG_SMP
EXPORT_SYMBOL(del_timer_sync);
#endif
+EXPORT_SYMBOL(add_timer);
+EXPORT_SYMBOL(del_timer);
EXPORT_SYMBOL(mod_timer);
+EXPORT_SYMBOL(__mod_timer);
#ifdef HAVE_DISABLE_HLT
EXPORT_SYMBOL(disable_hlt);
_
next prev parent reply other threads:[~2003-07-30 6:35 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-29 15:41 PATCH: Race in 2.6.0-test2 timer code linas
2003-07-29 20:56 ` Andrew Morton
2003-07-30 5:57 ` Ingo Molnar
2003-07-30 6:36 ` Andrew Morton [this message]
2003-07-30 7:07 ` Ingo Molnar
2003-07-30 7:34 ` Andrea Arcangeli
2003-07-30 7:34 ` Ingo Molnar
2003-07-30 8:28 ` Andrea Arcangeli
2003-07-30 10:31 ` Ingo Molnar
2003-07-30 11:16 ` Andrea Arcangeli
2003-07-30 11:49 ` Ingo Molnar
2003-07-30 12:34 ` Andrea Arcangeli
2003-07-30 21:18 ` linas
2003-07-30 22:06 ` Andrea Arcangeli
2003-07-30 22:17 ` Andrea Arcangeli
2003-07-31 7:04 ` Ingo Molnar
2003-07-30 21:19 ` Andrea Arcangeli
2003-07-30 23:43 ` linas
2003-07-30 23:56 ` Andrea Arcangeli
2003-07-30 23:54 ` Andrew Morton
2003-07-31 0:16 ` Andrea Arcangeli
2003-07-31 17:23 ` linas
2003-08-01 6:27 ` Ingo Molnar
2003-07-30 7:40 ` Ingo Molnar
2003-07-30 8:37 ` Andrea Arcangeli
2003-07-30 10:34 ` Ingo Molnar
2003-07-30 10:51 ` Andrew Morton
2003-07-30 11:28 ` Andrea Arcangeli
2003-07-30 11:22 ` Andrea Arcangeli
2003-07-30 20:05 ` linas
2003-07-31 6:50 ` Ingo Molnar
2003-07-31 22:56 ` linas
2003-08-01 6:23 ` Ingo Molnar
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