[tip:sched/core] sched: Fix cond_resched_lock() in !CONFIG_PREEMPT

[tip-bot for Frederic Weisbecker]

Commit-ID:  716a42348cdaf04534b15fbdc9c83e25baebfed5
Gitweb:     http://git.kernel.org/tip/716a42348cdaf04534b15fbdc9c83e25baebfed5
Author:     Frederic Weisbecker <fweisbec@xxxxxxxxx>
AuthorDate: Fri, 24 Jul 2009 20:05:23 +0200
Committer:  Ingo Molnar <mingo@xxxxxxx>
CommitDate: Sun, 2 Aug 2009 14:03:57 +0200

sched: Fix cond_resched_lock() in !CONFIG_PREEMPT

The might_sleep() test inside cond_resched_lock() assumes the
spinlock is held and then preemption is disabled. This is true
with CONFIG_PREEMPT but the preempt_count() doesn't change
otherwise.

Check by starting from the appropriate preempt offset depending
on the config.

Reported-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
LKML-Reference: <1248458723-12146-1-git-send-email-fweisbec@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>


---
 include/linux/sched.h |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index cbbfca6..c472414 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2293,8 +2293,14 @@ extern int _cond_resched(void);
 
 extern int __cond_resched_lock(spinlock_t *lock);
 
+#ifdef CONFIG_PREEMPT
+#define PREEMPT_LOCK_OFFSET	PREEMPT_OFFSET
+#else
+#define PREEMPT_LOCK_OFFSET	0
+#endif
+
 #define cond_resched_lock(lock) ({				\
-	__might_sleep(__FILE__, __LINE__, PREEMPT_OFFSET);	\
+	__might_sleep(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET);	\
 	__cond_resched_lock(lock);				\
 })
 
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