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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>
This commit is contained in:
Oleg Nesterov 2014-10-08 21:36:44 +02:00 committed by Ingo Molnar
parent 8f9fbf092c
commit 1a43a14a5b
1 changed files with 5 additions and 6 deletions
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11
kernel/sched/core.c
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@ -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);