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


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