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    SubjectRe: [BUG 2.6.25-rc3] scheduler/hotplug: some processes are dealocked when cpu is set to offline
    On Thu, Mar 06, 2008 at 04:45:25PM +0530, Gautham R Shenoy wrote:
    > On Wed, Mar 05, 2008 at 04:53:14PM +0300, Oleg Nesterov wrote:
    > > On 03/05, Gautham R Shenoy wrote:
    > > >
    > > > On Tue, Mar 04, 2008 at 06:01:07PM +0300, Oleg Nesterov wrote:
    > > > > On 03/04, Gautham R Shenoy wrote:
    > > > > >
    > > > > > So at times, the callback thread is blocked on kthread_stop(k) in
    > > > > > softlockup.c, while other time, it was blocked in
    > > > > > cleanup_workqueue_threads() in workqueue.c.
    > > > >
    > > > > >From another message:
    > > > > >
    > > > > > However, it remains in R< state
    > > > >
    > > > > What about cwq->thread? Was it TASK_RUNNING too?
    > > >
    > > > No, it was in TASK_UNINTERRUPTIBLE state. The last thing it ever
    > > > executed was the wait_for_completion in flush_cpu_workqueue()
    > >
    > > You misunderstood ;) The task doing _cpu_down() hang in flush_cpu_workqueue(),
    > > because cwq->thread doesn't want to die. But what was cwq->thread->state?
    > >
    >
    > Yup, sorry for that stupid reply.
    >
    > > Could you try the patch? Yi constantly sees the tasks in R< state.
    > > I am starting to suspect some scheduling issue.
    >
    > Me too. With your patch applied there were quite a few tasks in the
    > running state which didn't get the cpu for more than 120 seconds.
    >
    > I could be a scheduler problem which CPU-Hotplug is able to catch more
    > easily. Will try a git bisect.

    BTW, with your patch, I get the "task can't get CPU for more than
    120 seconds" message even while running a kernbench on 2.6.25-rc2.

    >
    >
    > >
    > > Oleg.
    >
    > --
    > Thanks and Regards
    > gautham

    --
    Thanks and Regards
    gautham


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