[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>
git-mirror · Jul 8, 2005 · 5bbcfd9 · 5bbcfd9
1 parent a4014d8
commit 5bbcfd9
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/kernel/sched.c b/kernel/sched.c
@@ -3877,6 +3877,13 @@ asmlinkage long sys_sched_yield(void)
 
 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();