[GIT pull] sched fix for 4.9

From: Thomas Gleixner
Date: Sat Oct 08 2016 - 09:34:10 EST


please pull the latest sched-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-for-linus

A revert of a commit which pointelessly widened a preempt disabled section
which in turn caused might_sleep() to trigger. The patch intended to
prevent usage of smp_processor_id() in preemptible context, but the usage
in that case is fine because the thread is pinned on a single cpu and
therefore cannot be migrated off.



Ingo Molnar (1):
Revert "sched/core: Do not use smp_processor_id() with preempt enabled in smpboot_thread_fn()"

kernel/smpboot.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/smpboot.c b/kernel/smpboot.c
index fc0d8270f69e..13bc43d1fb22 100644
--- a/kernel/smpboot.c
+++ b/kernel/smpboot.c
@@ -122,12 +122,12 @@ static int smpboot_thread_fn(void *data)

if (kthread_should_park()) {
+ preempt_enable();
if (ht->park && td->status == HP_THREAD_ACTIVE) {
BUG_ON(td->cpu != smp_processor_id());
td->status = HP_THREAD_PARKED;
- preempt_enable();
/* We might have been woken for stop */