From 4fa5cd5245b627db88c9ca08ae442373b02596b4 Mon Sep 17 00:00:00 2001
From: Con Kolivas <kernel@kolivas.org>
Date: Tue, 13 Sep 2016 16:27:05 +1000
Subject: 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>
---
 kernel/smpboot.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'kernel/smpboot.c')

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;
-- 
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