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SubjectRe: Bug in scheduler when using rt_mutex
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On Thu, 2011-01-20 at 15:06 +0800, Yong Zhang wrote:
> On Thu, Jan 20, 2011 at 2:12 PM, Mike Galbraith <efault@gmx.de> wrote:
> > If the task returns as a sleeper, place entity() will be called when it
> > is awakened, so it's sleep credit will be clipped as usual. So vruntime
> > can be much less than min_vruntime at class exit time, and it doesn't
> > matter, clipping on wakeup after re-entry takes care of it.. if that's
> > what you were thinking about.
>
> For a sleep task which stay in sched_fair before it's waked:
> try_to_wake_up()
> ttwu_activate()
> activate_task()
> enqueue_task_fair()
> enqueue_entity()
> place_entity() <== clip vruntime
>
> For a sleep task which promote to sched_rt when it's sleep:
> rt_mutex_setprio()
> check_class_changed()
> switch_from_fair() <== vruntime -= min_vruntime
> try_to_wake_up()
> ...run then stay on rq
> rt_mutex_setprio()
> enqueue_task_fair() <==vruntime += min_vruntime
>
> The difference is that in the second case, place_entity() is not
> called, but wrt sched_fair, the task is a WAKEUP task.
> Then we place this task in sched_fair before where it should be.

D'oh. You're right, he needs to be clipped before he leaves.

-Mike



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