Commit-ID: 1a43a14a5bd9c32dbd7af35e35a5afa703944bcb
Gitweb: http://git.kernel.org/tip/1a43a14a5bd9c32dbd7af35e35a5afa703944bcb
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Wed, 8 Oct 2014 21:36:44 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 28 Oct 2014 10:47:54 +0100
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@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Kirill Tkhai <tkhai@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20141008193644.GA32055@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/core.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index cde8481..b493560 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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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