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    SubjectRe: [PATCH][GIT PULL] tracing: Fix compile issue for trace_sched_wakeup.c
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    On Thu, 2010-10-21 at 07:01 -0400, Steven Rostedt wrote:
    > On Thu, 2010-10-21 at 09:22 +0200, Peter Zijlstra wrote:
    > > On Thu, 2010-10-21 at 11:58 +0900, Masami Hiramatsu wrote:
    > >
    > > > 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.
    > >
    > > There are people doing hotplug stress testing, that too results in heavy
    > > stop_machine usage.
    >
    > But with hotplug, isn't there a bit more time between stop machine
    > calls? That is, you need to do a bit of work to bring down or up a CPU,
    > and that will slow down the number of stop machine calls together.
    >
    > Here, we do a simple change and call stop machine() several times.
    >
    > Although, I agree, I do not think the bug is in stop machine itself, but
    > perhaps the way we are using it might have some niche anomaly that we
    > are hitting.

    Possibly, but wouldn't it make sense to batch up the work and simply
    call stop_machine only once? I mean, if you already know you're going to
    do this...



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