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    SubjectRe: [PATCH] sched: fix need_resched() when checking peempt
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    On Wed, 2011-05-25 at 12:34 +0800, Yong Zhang wrote:
    > On Wed, May 25, 2011 at 11:24 AM, Yong Zhang <yong.zhang0@gmail.com> wrote:
    > > On Tue, May 24, 2011 at 9:50 PM, Hillf Danton <dhillf@gmail.com> wrote:
    > >> On Tue, May 24, 2011 at 9:39 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
    > >>> On Tue, 2011-05-24 at 21:27 +0800, Hillf Danton wrote:
    > >>>> When checking if current task could be preempted by a newly woken task,
    > >>>> further check could be bypassed if the current thread is different from
    > >>>> the current task of run-queue, and it is corrected accordingly.
    > >>>
    > >>> Ug, that change log is an obfuscated mess. But looking at the actual
    > >>> patch, I figured what you wanted to say. How about this:
    > >>>
    > >>> ----
    > >>> The RT preempt check tests the wrong task if NEED_RESCHED is set. It
    > >>> currently checks the local CPU task. It is suppose to check the task
    > >>> that is running on the run queue we are about to wake another task on.
    > >>> ----
    > >>>
    > >> Thanks, it is great changelog:)
    > >
    > > Good catch.
    > >
    > > Reviewed-by: Yong Zhang <yong.zhang0@gmail.com>
    > >
    > > BTW, this may be the reason for we could trigger
    > > WARN_ON_ONCE(test_tsk_need_resched(next));
    > > https://lkml.org/lkml/2010/12/20/28
    > >
    > > Peter, Mike, how do you think about it?
    >
    > Since rq->lock protects both, that issue needs more digging :)

    Yeah, good rainy day project.

    -Mike



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