Re: [PATCH][GIT PULL] tracing: Fix compile issue for trace_sched_wakeup.c

Masami Hiramatsu
2010-10-21T02:59:07Z

(2010/10/21 1:43), Jason Baron wrote:
> On Wed, Oct 20, 2010 at 05:40:45PM +0200, Ingo Molnar wrote:
>> FYI, there's a new mystery hang (sometimes crash) that triggers in -tip - and which
>> seems to be tracing related. See the crashlog below - config attached.
>>
>> It's not bisectable - small changes in the kernel make the bug come/go. (might be a
>> race of some sorts)
>>
>> Thanks,
>>
>> Ingo
>>
>
> strange b/c it looks like we get though enabling/disabling the
> tracepoitns individually, but then when we go to enable all the
> tracepoints we hit this hang - perhaps, suggesting a race. Do we always
> fail after "Testing all events:" is printed? Does the crash have any
> more clues. I will try and re-produce this.
>
> Also, I noticed some recent changes to text_poke_smp() usage of
> stop_machine() on Oct. 14th. That's related to the area where this appears
> to hang, so if things were working with this .config before then, that
> might be a place to look. Adding Masami to the 'cc list.

Recent changes of text_poke_smp() just removed unnecessary
get/put_online_cpu(), so I think it's not related this bug.

It seems there can be a bug in stop_machine() routine under
heavy use. usually that is called just once at a time, but jump
label and optprobe might call it heavily (thousands times?).
So some racy situation can be happen easily.

Thanks,

>
> thanks,
>
> -Jason
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--
Masami HIRAMATSU
2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com