From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Simon Kirby <sim@hostway.ca>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Dave Jones <davej@redhat.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Ingo Molnar <mingo@elte.hu>
Subject: Re: Linux 3.1-rc9
Date: Tue, 18 Oct 2011 11:05:13 +0200
Message-ID: <1318928713.21167.4.camel@twins> (raw)
In-Reply-To: <alpine.LFD.2.02.1110181037120.3240@ionos>
On Tue, 2011-10-18 at 10:39 +0200, Thomas Gleixner wrote:
> On Mon, 17 Oct 2011, Thomas Gleixner wrote:
> > That said, I really need some sleep before I can make a final
> > judgement on that horror. The call paths are such an intermingled mess
> > that it's not funny anymore. I do that tomorrow morning first thing.
>
> The patch is safe and the exit race just existed in my confused tired
> brain. Peter, can you please provide a changelog. That wants a cc
> stable as well, because that deadlock causing commit hit 3.0.7 :(
---
Subject: cputimer: Cure lock inversion
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Mon Oct 17 11:50:30 CEST 2011
There's a lock inversion between the cputimer->lock and rq->lock; notably
the two callchains involved are:
update_rlimit_cpu()
sighand->siglock
set_process_cpu_timer()
cpu_timer_sample_group()
thread_group_cputimer()
cputimer->lock
thread_group_cputime()
task_sched_runtime()
->pi_lock
rq->lock
scheduler_tick()
rq->lock
task_tick_fair()
update_curr()
account_group_exec()
cputimer->lock
Where the first one is enabling a CLOCK_PROCESS_CPUTIME_ID timer, and
the second one is keeping up-to-date.
This problem was introduced by e8abccb7193 ("posix-cpu-timers: Cure
SMP accounting oddities").
Cure the problem by removing the cputimer->lock and rq->lock nesting,
this leaves concurrent enablers doing duplicate work, but the time
wasted should be on the same order otherwise wasted spinning on the
lock and the greater-than assignment filter should ensure we preserve
monotonicity.
Reported-by: Dave Jones <davej@redhat.com>
Reported-by: Simon Kirby <sim@hostway.ca>
Cc: stable@kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
kernel/posix-cpu-timers.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
Index: linux-2.6/kernel/posix-cpu-timers.c
===================================================================
--- linux-2.6.orig/kernel/posix-cpu-timers.c
+++ linux-2.6/kernel/posix-cpu-timers.c
@@ -274,9 +274,7 @@ void thread_group_cputimer(struct task_s
struct task_cputime sum;
unsigned long flags;
- spin_lock_irqsave(&cputimer->lock, flags);
if (!cputimer->running) {
- cputimer->running = 1;
/*
* The POSIX timer interface allows for absolute time expiry
* values through the TIMER_ABSTIME flag, therefore we have
@@ -284,8 +282,11 @@ void thread_group_cputimer(struct task_s
* it.
*/
thread_group_cputime(tsk, &sum);
+ spin_lock_irqsave(&cputimer->lock, flags);
+ cputimer->running = 1;
update_gt_cputime(&cputimer->cputime, &sum);
- }
+ } else
+ spin_lock_irqsave(&cputimer->lock, flags);
*times = cputimer->cputime;
spin_unlock_irqrestore(&cputimer->lock, flags);
}
next prev parent reply index
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-05 1:40 Linus Torvalds
2011-10-07 7:08 ` Simon Kirby
2011-10-07 17:48 ` Simon Kirby
2011-10-07 18:01 ` Peter Zijlstra
2011-10-08 0:33 ` Simon Kirby
2011-10-08 0:50 ` Simon Kirby
2011-10-08 7:55 ` Peter Zijlstra
2011-10-12 21:35 ` Simon Kirby
2011-10-13 23:25 ` Simon Kirby
2011-10-17 1:39 ` Linus Torvalds
2011-10-17 4:58 ` Ingo Molnar
2011-10-17 9:03 ` Thomas Gleixner
2011-10-17 10:40 ` Peter Zijlstra
2011-10-17 11:40 ` Alan Cox
2011-10-17 18:49 ` Ingo Molnar
2011-10-17 20:35 ` H. Peter Anvin
2011-10-17 21:19 ` Ingo Molnar
2011-10-17 21:22 ` H. Peter Anvin
2011-10-17 21:39 ` Ingo Molnar
2011-10-17 22:03 ` Ingo Molnar
2011-10-17 22:04 ` Ingo Molnar
2011-10-17 22:08 ` H. Peter Anvin
2011-10-18 6:01 ` Ingo Molnar
2011-10-18 7:12 ` Geert Uytterhoeven
2011-10-18 18:50 ` H. Peter Anvin
2011-10-17 21:31 ` Ingo Molnar
2011-10-17 7:55 ` Martin Schwidefsky
2011-10-17 9:12 ` Peter Zijlstra
2011-10-17 9:18 ` Martin Schwidefsky
2011-10-17 20:48 ` H. Peter Anvin
2011-10-18 7:20 ` Martin Schwidefsky
2011-10-17 10:34 ` Peter Zijlstra
2011-10-17 14:07 ` Martin Schwidefsky
2011-10-17 14:57 ` Linus Torvalds
2011-10-17 17:54 ` Peter Zijlstra
2011-10-17 18:31 ` Linus Torvalds
2011-10-17 19:23 ` Peter Zijlstra
2011-10-17 21:00 ` Thomas Gleixner
2011-10-18 8:39 ` Thomas Gleixner
2011-10-18 9:05 ` Peter Zijlstra [this message]
2011-10-18 14:59 ` Linus Torvalds
2011-10-18 15:26 ` Thomas Gleixner
2011-10-18 18:07 ` Ingo Molnar
2011-10-18 18:14 ` [GIT PULL] timer fix Ingo Molnar
2011-10-18 16:13 ` Linux 3.1-rc9 Dave Jones
2011-10-18 18:20 ` Simon Kirby
2011-10-18 19:48 ` Thomas Gleixner
2011-10-18 20:12 ` Linus Torvalds
2011-10-25 15:26 ` Simon Kirby
2011-10-26 1:47 ` Yong Zhang
2011-10-24 19:02 ` Simon Kirby
2011-10-25 7:13 ` Linus Torvalds
2011-10-25 9:01 ` David Miller
2011-10-25 12:30 ` Thomas Gleixner
2011-10-25 23:18 ` David Miller
2011-10-25 20:20 ` Simon Kirby
2011-10-31 17:32 ` Simon Kirby
2011-11-02 16:40 ` Thomas Gleixner
2011-11-02 17:27 ` Eric Dumazet
2011-11-02 17:46 ` Linus Torvalds
2011-11-02 17:53 ` Eric Dumazet
2011-11-02 18:00 ` Linus Torvalds
2011-11-02 18:05 ` Eric Dumazet
2011-11-02 18:10 ` Linus Torvalds
2011-11-02 17:49 ` Eric Dumazet
2011-11-02 17:58 ` Eric Dumazet
2011-11-02 19:16 ` Simon Kirby
2011-11-02 22:42 ` Eric Dumazet
2011-11-03 0:24 ` Thomas Gleixner
2011-11-03 0:52 ` Simon Kirby
2011-11-03 22:07 ` David Miller
2011-11-03 6:06 ` Jörg-Volker Peetz
2011-11-03 6:26 ` Eric Dumazet
2011-11-03 6:43 ` David Miller
2011-11-02 17:54 ` Thomas Gleixner
2011-11-02 18:04 ` Eric Dumazet
2011-11-02 18:28 ` Simon Kirby
2011-11-02 18:30 ` Thomas Gleixner
2011-11-02 22:10 ` Steven Rostedt
2011-11-02 23:00 ` Steven Rostedt
2011-11-03 0:09 ` Simon Kirby
2011-11-03 0:15 ` Steven Rostedt
2011-11-03 0:17 ` Simon Kirby
2011-11-18 23:11 ` [tip:perf/core] lockdep: Show subclass in pretty print of lockdep output tip-bot for Steven Rostedt
2011-10-20 14:36 ` Linux 3.1-rc9 Martin Schwidefsky
2011-10-23 11:34 ` Ingo Molnar
2011-10-24 7:48 ` Martin Schwidefsky
2011-10-24 7:51 ` Linus Torvalds
2011-10-24 8:08 ` Martin Schwidefsky
2011-10-18 5:40 ` Simon Kirby
2011-10-09 20:51 ` Arkadiusz Miśkiewicz
2011-10-10 2:29 ` [tpmdd-devel] " Stefan Berger
2011-10-10 16:23 ` Rajiv Andrade
2011-10-10 17:05 ` Arkadiusz Miśkiewicz
2011-10-10 17:22 ` Stefan Berger
2011-10-10 17:57 ` Arkadiusz Miśkiewicz
2011-10-10 21:08 ` Arkadiusz Miśkiewicz
2011-10-11 7:09 ` [tpmdd-devel] " Peter.Huewe
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