From: Ingo Molnar <mingo@elte.hu>
Date: Fri, 8 Jul 2005 00:57:04 +0000 (-0700)
Subject: [PATCH] cond_resched(): fix bogus might_sleep() warning
X-Git-Tag: v2.6.13-rc3~243
X-Git-Url: http://ftp.safe.ca/?a=commitdiff_plain;h=5bbcfd9000887c0da7d57cc7b3ac869fc0dd5aa9;p=safe%2Fjmp%2Flinux-2.6

[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>
---

diff --git a/kernel/sched.c b/kernel/sched.c
index 5f2182d..4107db0 100644
--- 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();