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SubjectRe: Bug in scheduler when using rt_mutex
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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.

Thanks,
Yong

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