[PATCH] sched: Fix cond_resched_lock() in !CONFIG_PREEMPT

[Frederic Weisbecker <fweisbec@gmail.com>]

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@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---
 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 cb070dc..2c35bc2 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2294,8 +2294,14 @@ 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);				\
 })
 
-- 
1.6.2.3