linux-kernel - [PATCH] sched: Fix cond_resched_lock() in !CONFIG

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Message-Id: <1248458723-12146-1-git-send-email-fweisbec@gmail.com>
Date:	Fri, 24 Jul 2009 20:05:23 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH] 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@...fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Peter Zijlstra <peterz@...radead.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

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