From: Gautham R Shenoy <ego@in.ibm.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Jiri Slaby <jirislaby@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, "Rafael J. Wysocki" <rjw@sisk.pl>,
Arjan van de Ven <arjan@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Linux-pm mailing list <linux-pm@lists.linux-foundation.org>,
Dipankar Sarma <dipankar@in.ibm.com>
Subject: Re: broken suspend (sched related) [Was: 2.6.24-rc4-mm1]
Date: Mon, 10 Dec 2007 13:49:52 +0530 [thread overview]
Message-ID: <20071210081952.GA7215@in.ibm.com> (raw)
In-Reply-To: <20071209074647.GE22981@elte.hu>
On Sun, Dec 09, 2007 at 08:46:47AM +0100, Ingo Molnar wrote:
>
> * Jiri Slaby <jirislaby@gmail.com> wrote:
>
> > On 12/08/2007 04:24 PM, Ingo Molnar wrote:
> > > i'm wondering why it had no effect now
> >
> > diff --git a/kernel/cpu.c b/kernel/cpu.c
> > index e0d3a4f..a46c252 100644
> > --- a/kernel/cpu.c
> > +++ b/kernel/cpu.c
> > @@ -47,15 +47,21 @@ void __init cpu_hotplug_init(void)
> > }
> >
> > #ifdef CONFIG_HOTPLUG_CPU
> > -
> > +#include <asm/io.h>
> > void get_online_cpus(void)
> > {
> > + outb(0x20, 0x80);
> > might_sleep();
> > + outb(0x21, 0x80);
>
> ah. If you comment out get_online_cpus()/put_online_cpus() from
> kernel/softlockup.c, does it start working?
>
> Gautham, any ideas?
Hi Ingo,
>From the code I fail to see how get_online_cpus() can help us.
+ /*
+ * Only do the hung-tasks check on one CPU:
+ */
+ get_online_cpus();
+ check_cpu = any_online_cpu(cpu_online_map);
+ put_online_cpus();
check_cpu can go offline here, no?
+
+ if (this_cpu != check_cpu)
+ continue;
+
+ if (sysctl_hung_task_timeout_secs)
+ check_hung_uninterruptible_tasks(this_cpu);
Further more this can cause a deadlock since we're calling
get_online_cpus() from the watchdog thread's context,
which is going to be kthread_stop'ed from a cpu-hotplug context.
This is what I think was happening in the case reported by Jiri.
Please find the patch below.
Thanks and Regards
gautham.
commit 15bfb662b35c609490185fba2fd4713d230b9374
Author: Gautham R Shenoy <ego@in.ibm.com>
Date: Mon Dec 10 13:41:45 2007 +0530
softlockup: remove get_online_cpus() which doesn't help here.
The get_online_cpus() protection seems to be bogus
in kernel/softlockup.c as cpu cached in check_cpu can go offline
once we do a put_online_cpus().
This can also cause deadlock during a cpu offline as follows:
WATCHDOG_THREAD: OFFLINE_CPU:
mutex_down(&cpu_hotplug.lock);
/* All subsequent get_online_cpus
* will be blocked till we're
* done with this cpu-hotplug
* operation.
*/
get_online_cpus();
/* watchdog is blocked
Thus we cannot
go further until
the cpu-hotplug
operation completes
*/
CPU_DEAD:
kthread_stop(watchdog_thread);
/* we're trying to stop a
* thread which is blocked
* waiting for us to finish.
*
* Since we cannot finish until
* the thread stops, we deadlock here!
*/
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linuxtronix.de>
Cc: Arjan van de Van <arjan@linux.intel.com>
Cc: Jiri Slaby <jirislaby@gmail.com>
diff --git a/kernel/softlockup.c b/kernel/softlockup.c
index e50b44a..576eb9c 100644
--- a/kernel/softlockup.c
+++ b/kernel/softlockup.c
@@ -219,9 +219,7 @@ static int watchdog(void *__bind_cpu)
/*
* Only do the hung-tasks check on one CPU:
*/
- get_online_cpus();
check_cpu = any_online_cpu(cpu_online_map);
- put_online_cpus();
if (this_cpu != check_cpu)
continue;
--
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
next prev parent reply other threads:[~2007-12-10 10:04 UTC|newest]
Thread overview: 112+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-05 5:17 2.6.24-rc4-mm1 Andrew Morton
2007-12-05 9:15 ` 2.6.24-rc4-mm1: kobj changes fallout on powerpc Olof Johansson
2007-12-05 13:11 ` Kamalesh Babulal
2007-12-05 15:46 ` Greg KH
2007-12-05 14:12 ` 2.6.24-rc4-mm1 kobject changes broken with hvcs driver " Kamalesh Babulal
2007-12-05 15:47 ` Greg KH
2007-12-06 18:19 ` Balbir Singh
2007-12-06 18:50 ` Greg KH
2007-12-06 18:49 ` Kamalesh Babulal
2007-12-06 18:58 ` Balbir Singh
2007-12-06 19:21 ` Badari Pulavarty
2007-12-07 1:29 ` Balbir Singh
2007-12-06 20:31 ` Greg KH
2007-12-06 23:54 ` Badari Pulavarty
2007-12-07 0:32 ` Greg KH
2007-12-07 3:02 ` Kamalesh Babulal
2007-12-07 5:14 ` Greg KH
2007-12-07 22:01 ` Balbir Singh
2007-12-05 23:41 ` 2.6.24-rc4-mm1: hostbyte=0x01 driverbyte=0x00 (now bisected) Alexey Dobriyan
2007-12-06 7:52 ` Hannes Reinecke
2007-12-06 12:08 ` Jens Axboe
2007-12-06 19:19 ` Alexey Dobriyan
2007-12-06 3:15 ` 2.6.24-rc4-mm1 Kernel build fails on S390x Kamalesh Babulal
2007-12-06 7:19 ` Andrew Morton
2007-12-06 6:59 ` 2.6.24-rc4-mm1 Reuben Farrelly
2007-12-06 7:09 ` 2.6.24-rc4-mm1 David Miller
2007-12-07 13:16 ` 2.6.24-rc4-mm1 Ilpo Järvinen
2007-12-12 17:57 ` 2.6.24-rc4-mm1 Cedric Le Goater
2007-12-06 7:35 ` 2.6.24-rc4-mm1 Andrew Morton
2007-12-10 12:24 ` 2.6.24-rc4-mm1 Ilpo Järvinen
2007-12-10 20:05 ` 2.6.24-rc4-mm1 Ilpo Järvinen
2007-12-12 19:21 ` 2.6.24-rc4-mm1 Cedric Le Goater
2007-12-13 17:38 ` tcp_sacktag_one() WARNING (was Re: 2.6.24-rc4-mm1) Cedric Le Goater
2007-12-06 11:49 ` 2.6.24-rc4-mm1 Valdis.Kletnieks
2007-12-06 12:04 ` 2.6.24-rc4-mm1 Andrew Morton
2007-12-06 19:18 ` 2.6.24-rc4-mm1 Valdis.Kletnieks
2007-12-06 19:38 ` 2.6.24-rc4-mm1 Greg KH
2007-12-06 20:04 ` 2.6.24-rc4-mm1 Valdis.Kletnieks
2007-12-06 22:04 ` [dm-devel] 2.6.24-rc4-mm1 Kay Sievers
2007-12-06 22:12 ` Alasdair G Kergon
2007-12-06 23:12 ` Valdis.Kletnieks
2007-12-06 23:24 ` Kay Sievers
2007-12-07 18:20 ` Valdis.Kletnieks
2007-12-07 18:44 ` Kay Sievers
2007-12-07 20:28 ` Valdis.Kletnieks
2007-12-07 20:49 ` Kay Sievers
2007-12-06 22:28 ` 2.6.24-rc4-mm1: VDSOSYM build error Laurent Riffard
2007-12-06 22:37 ` Andrew Morton
2007-12-06 23:28 ` Miles Lane
2007-12-06 23:34 ` Andrew Morton
2007-12-06 23:47 ` Miles Lane
2007-12-07 10:36 ` Ingo Molnar
2007-12-07 1:14 ` [PATCH x86/mm] x86 vDSO: canonicalize sysenter .eh_frame Roland McGrath
2007-12-07 1:27 ` Harvey Harrison
2007-12-07 3:27 ` Miles Lane
2007-12-07 9:44 ` Ingo Molnar
2007-12-07 2:12 ` 2.6.24-rc4-mm1 Dave Young
2007-12-07 22:22 ` 2.6.24-rc4-mm1 Luis R. Rodriguez
2007-12-10 1:07 ` 2.6.24-rc4-mm1 Dave Young
2007-12-09 17:55 ` 2.6.24-rc4-mm1 Nick Kossifidis
[not found] ` <E1J0Yfy-0001V7-Rr@localhost>
2007-12-07 8:35 ` [PATCH BUGFIX] hid: the `bit' in hidinput_mapping_quirks() is an out parameter Fengguang Wu
2007-12-10 10:03 ` Jiri Kosina
2007-12-07 14:34 ` broken suspend (sched related) [Was: 2.6.24-rc4-mm1] Jiri Slaby
2007-12-07 15:11 ` Ingo Molnar
2007-12-07 17:51 ` Ingo Molnar
2007-12-08 8:10 ` Jiri Slaby
2007-12-08 8:39 ` Ingo Molnar
2007-12-08 9:23 ` Jiri Slaby
2007-12-08 15:24 ` Ingo Molnar
2007-12-08 17:34 ` Jiri Slaby
2007-12-08 17:43 ` Jiri Slaby
2007-12-09 8:06 ` Ingo Molnar
2007-12-08 23:12 ` Jiri Slaby
2007-12-09 7:46 ` Ingo Molnar
2007-12-09 9:09 ` Jiri Slaby
2007-12-10 8:19 ` Gautham R Shenoy [this message]
2007-12-10 8:55 ` Jiri Slaby
2007-12-10 9:10 ` Ingo Molnar
2007-12-10 10:15 ` Gautham R Shenoy
2007-12-10 10:21 ` Ingo Molnar
2007-12-10 11:08 ` Gautham R Shenoy
2007-12-10 11:28 ` Ingo Molnar
2007-12-10 11:49 ` Gautham R Shenoy
2007-12-10 9:29 ` Ingo Molnar
2007-12-07 18:20 ` [PATCH] md: balance braces in raid5 debug code Mariusz Kozlowski
2007-12-08 0:04 ` 2.6.24-rc4-mm1: undefined reference to `compat_sys_timerfd' on sparc64 Mariusz Kozlowski
2007-12-08 0:08 ` Andrew Morton
2007-12-08 9:17 ` Mariusz Kozlowski
2007-12-11 10:15 ` David Miller
2007-12-08 18:20 ` 2.6.24-rc4-mm1: some issues " Mariusz Kozlowski
2007-12-08 18:22 ` Andrew Morton
2007-12-09 8:45 ` David Miller
2007-12-09 9:03 ` Andrew Morton
2007-12-10 14:48 ` 2.6.24-rc4-mm1 Reuben Farrelly
2007-12-10 21:11 ` 2.6.24-rc4-mm1 Andrew Morton
2007-12-11 14:12 ` 2.6.24-rc4-mm1 Reuben Farrelly
2007-12-11 16:20 ` 2.6.24-rc4-mm1 Martin Bligh
2007-12-11 16:59 ` 2.6.24-rc4-mm1 Randy Dunlap
2007-12-11 17:50 ` 2.6.24-rc4-mm1 Martin Bligh
[not found] ` <33307c790712110813h23def95dvd068b7226e9fcd36@mail.gmail.com>
2007-12-11 20:37 ` 2.6.24-rc4-mm1 Andrew Morton
2007-12-11 21:20 ` 2.6.24-rc4-mm1 Ingo Molnar
2007-12-11 21:26 ` 2.6.24-rc4-mm1 Kok, Auke
2007-12-11 21:59 ` 2.6.24-rc4-mm1 Kok, Auke
2007-12-11 22:10 ` 2.6.24-rc4-mm1 Andrew Morton
2007-12-11 22:17 ` 2.6.24-rc4-mm1 Kok, Auke
2007-12-11 23:15 ` 2.6.24-rc4-mm1 Randy Dunlap
2007-12-12 4:16 ` 2.6.24-rc4-mm1 Rik van Riel
2007-12-13 17:45 ` 2.6.24-rc4-mm1 - BUG in tcp_fragment Cedric Le Goater
2007-12-13 23:00 ` Ilpo Järvinen
2007-12-14 6:52 ` Cedric Le Goater
2007-12-14 20:14 ` [PATCH net-2.6.25] Revert recent TCP work Ilpo Järvinen
2007-12-16 22:21 ` David Miller
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