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Commit 1a43a14a authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

sched: Fix schedule_tail() to disable preemption 



finish_task_switch() enables preemption, so post_schedule(rq) can be
called on the wrong (and even dead) CPU. Afaics, nothing really bad
can happen, but in this case we can wrongly clear rq->post_schedule
on that CPU. And this simply looks wrong in any case.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20141008193644.GA32055@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 8f9fbf09

kernel/sched/core.c

+5 −6
Original line number Diff line number Diff line
@@ -2309,15 +2309,14 @@ static inline void post_schedule(struct rq *rq) 
asmlinkage __visible void schedule_tail(struct task_struct *prev)

	__releases(rq->lock)

{

	struct rq *rq = this_rq();

	struct rq *rq;



	/* finish_task_switch() drops rq->lock and enables preemtion */

	preempt_disable();

	rq = this_rq();

	finish_task_switch(rq, prev);



	/*

	 * FIXME: do we need to worry about rq being invalidated by the

	 * task_switch?

	 */

	post_schedule(rq);

	preempt_enable();



	if (current->set_child_tid)

		put_user(task_pid_vnr(current), current->set_child_tid);