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    SubjectRe: [PATCH][GIT PULL] tracing: Fix compile issue for trace_sched_wakeup.c
    On Fri, Oct 22, 2010 at 10:14:31AM +0200, Peter Zijlstra wrote:
    > On Thu, 2010-10-21 at 21:44 -0400, Jason Baron wrote:
    >
    > > I finally found that we actually continue to run after the above
    > > apparent 'hang'. That is, we continue to make progress updating the jump
    > > labels. And doing a dump of all the system tasks at the time of the hang
    > > showed the processes in various places besides the stop machine threads.
    > > Thus, I thought that perhaps, for some reason the stop machine threads
    > > weren't being scheduled.
    > >
    > > Thus, I tried commenting out the special scheduling that is set up for
    > > stop machine threads, and that fixed the hang. I haven't yet looked into
    > > what might be going wrong with that scheduling...but maybe somebody else
    > > knows...
    >
    > Hrmm, so are you saying rq->stop was runnable but not running?

    yes, that's what it seems like.

    >
    > That would imply broken wakeup-preemption, does something like the below
    > cure that?
    >
    >

    no still seeing the same hang with the below patch...also, as a data point I
    backed out the patch that adds the stop_sched_class and that resolved the hang
    as well - just as a data point.

    thanks,

    -Jason

    > ---
    > kernel/sched_stoptask.c | 1 +
    > 1 files changed, 1 insertions(+), 0 deletions(-)
    >
    > diff --git a/kernel/sched_stoptask.c b/kernel/sched_stoptask.c
    > index 45bddc0..50ad10f 100644
    > --- a/kernel/sched_stoptask.c
    > +++ b/kernel/sched_stoptask.c
    > @@ -35,6 +35,7 @@ static struct task_struct *pick_next_task_stop(struct rq *rq)
    > static void
    > enqueue_task_stop(struct rq *rq, struct task_struct *p, int flags)
    > {
    > + resched_cpu(cpu_of(rq));
    > }
    >
    > static void
    >
    >


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