Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit f31e11d8 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

wait_task_inactive(): don't consider task->nivcsw 



If wait_task_inactive() returns success the task was deactivated.  In that
case schedule() always increments ->nvcsw which alone can be used as a
"generation counter".

If the next call returns the same number, we can be sure that the task was
unscheduled.  Otherwise, because we know that .on_rq == 0 again, ->nvcsw
should have been changed in between.

Q: perhaps it is better to do "ncsw = (p->nvcsw << 1) | 1" ?  This
decreases the possibility of "was it unscheduled" false positive when
->nvcsw == 0.

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 94d3d824

kernel/sched.c

+2 −5
Original line number Diff line number Diff line
@@ -1921,11 +1921,8 @@ unsigned long wait_task_inactive(struct task_struct *p, long match_state) 
		running = task_running(rq, p);

		on_rq = p->se.on_rq;

		ncsw = 0;

		if (!match_state || p->state == match_state) {

			ncsw = p->nivcsw + p->nvcsw;

			if (unlikely(!ncsw))

				ncsw = 1;

		}

		if (!match_state || p->state == match_state)

			ncsw = p->nvcsw ?: 1;

		task_rq_unlock(rq, &flags);



		/*