On Fri, 2009-09-25 at 06:20 +0000, tip-bot for Martin Schwidefsky wrote:
> Commit-ID: 89133f93508137231251543d1732da638e6022e1
> Gitweb: http://git.kernel.org/tip/89133f93508137231251543d1732da638e6022e1
> Author: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> AuthorDate: Thu, 24 Sep 2009 17:29:52 +0200
> Committer: Ingo Molnar <mingo@xxxxxxx>
> CommitDate: Thu, 24 Sep 2009 22:37:53 +0200
>
> clocksource: Resume clocksource without taking the clocksource mutex
>
> git commit 75c5158f70c065b9 converted the clocksource spinlock to a
> mutex. This causes the following BUG:
>
> BUG: sleeping function called from invalid context at
> kernel/mutex.c:280 in_atomic(): 0, irqs_disabled(): 1, pid: 2473,
> name: pm-suspend 2 locks held by pm-suspend/2473:
> #0: (&buffer->mutex){......}, at: [<ffffffff8115ab13>]
> sysfs_write_file+0x3c/0x137
> #1: (pm_mutex){......}, at: [<ffffffff810865b5>]
> enter_state+0x39/0x130 Pid: 2473, comm: pm-suspend Not tainted 2.6.31
> #1 Call Trace:
> [<ffffffff810792f0>] ? __debug_show_held_locks+0x22/0x24
> [<ffffffff8104a2ef>] __might_sleep+0x107/0x10b
> [<ffffffff8141fca9>] mutex_lock_nested+0x25/0x43
> [<ffffffff81073537>] clocksource_resume+0x1c/0x60
> [<ffffffff81072902>] timekeeping_resume+0x1e/0x1c8
> [<ffffffff812aee62>] __sysdev_resume+0x25/0xcf
> [<ffffffff812aef79>] sysdev_resume+0x6d/0xae
> [<ffffffff810864f8>] suspend_devices_and_enter+0x12b/0x1af
> [<ffffffff8108665b>] enter_state+0xdf/0x130
> [<ffffffff81085dc3>] state_store+0xb6/0xd3
> [<ffffffff81204c73>] kobj_attr_store+0x17/0x19
> [<ffffffff8115abd2>] sysfs_write_file+0xfb/0x137
> [<ffffffff811057d2>] vfs_write+0xae/0x10b
> [<ffffffff81208392>] ? __up_read+0x1a/0x7f
> [<ffffffff811058ef>] sys_write+0x4a/0x6e
> [<ffffffff81011b82>] system_call_fastpath+0x16/0x1b
>
> clocksource_resume is called early in the resume process, there is
> only one cpu, no processes are running and the interrupts are
> disabled. It is therefore possible to resume the clocksources
> without taking the clocksource mutex.
Should a comment to this effect be included in the code?
thanks
-john
> Reported-by: Xiaotian Feng <xtfeng@xxxxxxxxx>
> Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> Tested-by: Michal Schmidt <mschmidt@xxxxxxxxxx>
> Cc: Xiaotian Feng <xtfeng@xxxxxxxxx>
> Cc: John Stultz <johnstul@xxxxxxxxxx>
> LKML-Reference: <20090924172952.49697825@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
>
>
> ---
> kernel/time/clocksource.c | 4 ----
> 1 files changed, 0 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
> index 0911334..5e18c6a 100644
> --- a/kernel/time/clocksource.c
> +++ b/kernel/time/clocksource.c
> @@ -394,15 +394,11 @@ void clocksource_resume(void)
> {
> struct clocksource *cs;
>
> - mutex_lock(&clocksource_mutex);
> -
> list_for_each_entry(cs, &clocksource_list, list)
> if (cs->resume)
> cs->resume();
>
> clocksource_resume_watchdog();
> -
> - mutex_unlock(&clocksource_mutex);
> }
>
> /**
--
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