Commit 1a43a14a authored Oct 08, 2014 by Oleg Nesterov Committed by Ingo Molnar Oct 28, 2014

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: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter 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: Ingo 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);

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