[PATCH] cond_resched(): fix bogus might_sleep() warning

The BKS might be reacquired before we have dropped PREEMPT_ACTIVE, which could trigger a second could trigger a second cond_resched() call. Bug found by Hirofumi Ogawa. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[PATCH] cond_resched(): fix bogus might_sleep() warning
The BKS might be reacquired before we have dropped PREEMPT_ACTIVE, which could trigger a second could trigger a second cond_resched() call. Bug found by Hirofumi Ogawa. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Ingo Molnar · Linus Torvalds
1 parent a4014d8f61
Showing 1 changed file with 7 additions and 0 deletions Side-by-side Diff
kernel/sched.c
@@ -3877,6 +3877,13 @@
  
 static inline void __cond_resched(void)
 {
+	/*
+	 * The BKS might be reacquired before we have dropped
+	 * PREEMPT_ACTIVE, which could trigger a second
+	 * cond_resched() call.
+	 */
+	if (unlikely(preempt_count()))
+		return;
 	do {
 		add_preempt_count(PREEMPT_ACTIVE);
 		schedule();
...	...	@@ -3877,6 +3877,13 @@
3877	3877
3878	3878	static inline void __cond_resched(void)
3879	3879	{
	3880	+ /*
	3881	+ * The BKS might be reacquired before we have dropped
	3882	+ * PREEMPT_ACTIVE, which could trigger a second
	3883	+ * cond_resched() call.
	3884	+ */
	3885	+ if (unlikely(preempt_count()))
	3886	+ return;
3880	3887	do {
3881	3888	add_preempt_count(PREEMPT_ACTIVE);
3882	3889	schedule();