Messages in this thread | | | Date | Thu, 10 Jul 2008 09:30:55 +0200 | From | Heiko Carstens <> | Subject | Re: [BUG] CFS vs cpu hotplug |
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On Thu, Jul 10, 2008 at 12:32:40AM +0200, Dmitry Adamushko wrote: > > hm, while looking at this code again... > > > Ingo, > > I think we may have a race between try_to_wake_up() and migrate_live_tasks() -> move_task_off_dead_cpu() > when the later one may end up looping endlessly. > > > Subject: sched: prevent a potentially endless loop in move_task_off_dead_cpu() > > Interrupts are enabled on other CPUs when migration_call(CPU_DEAD, ...) is called so we may get a race > between try_to_wake_up() and migrate_live_tasks() -> move_task_off_dead_cpu(). The former one may push > a task out of a dead CPU causing the later one to loop endlessly.
That's exactly what explains a dump I got yesterday. Thanks for fixing! :)
Will apply your patch and let you know if it fixes the problem. (may take until next week unfortunately).
> Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com> > > --- > diff --git a/kernel/sched.c b/kernel/sched.c > index 94ead43..9397b87 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -5621,8 +5621,10 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu) > > double_rq_lock(rq_src, rq_dest); > /* Already moved. */ > - if (task_cpu(p) != src_cpu) > + if (task_cpu(p) != src_cpu) { > + ret = 1; > goto out; > + } > /* Affinity changed (again). */ > if (!cpu_isset(dest_cpu, p->cpus_allowed)) > goto out; > > --- >
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