sched/core: Do not use smp_processor_id() with preempt enabled in smpboot_thread_fn()

We should not be using smp_processor_id() with preempt enabled.

Bug identified and fix provided by Alfred Chen.

Reported-by: Alfred Chen <cchalpha@gmail.com>
Signed-off-by: Con Kolivas <kernel@kolivas.org>
Cc: Alfred Chen <cchalpha@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/2042051.3vvUWIM0vs@hex
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/smpboot.c b/kernel/smpboot.c
index 13bc43d1fb22..fc0d8270f69e 100644
--- a/kernel/smpboot.c
+++ b/kernel/smpboot.c
@@ -122,12 +122,12 @@ static int smpboot_thread_fn(void *data)
 
                 if (kthread_should_park()) {
                         __set_current_state(TASK_RUNNING);
-                        preempt_enable();
                         if (ht->park && td->status == HP_THREAD_ACTIVE) {
                                 BUG_ON(td->cpu != smp_processor_id());
                                 ht->park(td->cpu);
                                 td->status = HP_THREAD_PARKED;
                         }
+                        preempt_enable();
                         kthread_parkme();
                         /* We might have been woken for stop */
                         continue;