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SubjectRe: [PATCH tracing/kprobes] kprobes: Disable booster when CONFIG_PREEMPT=y
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On Fri, 2010-01-29 at 12:08 -0500, Mathieu Desnoyers wrote:
>
> If a task is set as stopped, and the preempted before calling schedule,
> can this result in a preempted task staying in that state for an
> arbitrary long period of time ? Or is there some mechanism prohibiting
> that in the scheduler ?

PREEMPT_ACTIVE does that:

preempt_schedule()
add_preempt_count(PREEMPT_ACTIVE);
schedule();


schedule()
if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
if (unlikely(signal_pending_state(prev->state, prev)))
prev->state = TASK_RUNNING;
else
deactivate_task(rq, prev, 1);
switch_count = &prev->nvcsw;
}



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