lkml.org 
[lkml]   [2009]   [Jul]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] softlockup: fix problem with long kernel pauses from kgdb
Peter Zijlstra wrote:
> On Mon, 2009-07-27 at 15:03 -0500, Jason Wessel wrote:
>
>> The fix is to simply invoke sched_clock_tick() to update "cpu sched
>> clock" on exit from kgdb_handle_exception.
>>
>
> Is that a regular IRQ context, or is that NMI context?
>
>

The patch text there is incorrect (which I can fix), because there were
3 other versions of this particular patch. The version of this patch
that tried to use sched_clock_tick() from the exception context hung the
system because there was lock contention for CPUs that were not in the
running state.

In this version, the sched_clock_tick() added in the softlockup_tick(),
which did not result in a hard hang. I am pretty sure that
softlockup_tick() runs as a part of the timer interrupt processing from
run_local_timers(), so there was no further need to turn off the interrupts.

Jason.

>> Signed-off-by: Dongdong Deng <Dongdong.Deng@windriver.com>
>> Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
>> Cc: Ingo Molnar <mingo@elte.hu>
>> Cc: peterz@infradead.org
>> ---
>> kernel/softlockup.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> --- a/kernel/softlockup.c
>> +++ b/kernel/softlockup.c
>> @@ -118,6 +118,9 @@ void softlockup_tick(void)
>> }
>>
>> if (touch_timestamp == 0) {
>> + /* If the time stamp was touched externally make sure the
>> + * scheduler tick is up to date as well */
>> + sched_clock_tick();
>> __touch_softlockup_watchdog();
>> return;
>> }
>>
>>
>
> Aside from the funny comment style (please fix) the fix does look
> sensible.
>

No problem.

Thanks,
Jason.


\
 
 \ /
  Last update: 2009-07-27 23:29    [from the cache]
©2003-2011 Jasper Spaans