linux-kernel - [PATCH 6/7 v3] sched: Pull up the might_sleep() check in cond

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Date:	Thu, 16 Jul 2009 02:28:13 -0400
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 6/7 v3] sched: Pull up the might_sleep() check in cond_resched()

might_sleep() is called lately in cond_resched(), after the
need_resched()/preempt enabled/system running tests are checked.

It's better to check the sleeps while atomic earlier and not depend
on some environment datas that reduce the chances to detect a
problem.

Also define cond_resched_*() helpers as macros, so that the FILE/LINE
reported in the sleeping while atomic warning displays the real origin
and not sched.h

Changes in v2:
- call __might_sleep() directly instead of might_sleep() which may call
  cond_resched()
- turn cond_resched() into a macro so that the file:line couple reported
  refers to the caller of cond_resched() and not __cond_resched() itself.

Changes in v3:
- also propagate this __might_sleep() pull up to cond_resched_lock() and
  cond_resched_softirq()

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 fs/dcache.c           |    1 +
 include/linux/sched.h |   29 +++++++++++++++++++----------
 kernel/sched.c        |   12 +++++-------
 3 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 5ecb8e1..64698d6 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -32,6 +32,7 @@
 #include <linux/swap.h>
 #include <linux/bootmem.h>
 #include <linux/fs_struct.h>
+#include <linux/hardirq.h>
 #include "internal.h"
 
 int sysctl_vfs_cache_pressure __read_mostly = 100;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index e2bdf18..099408f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2286,17 +2286,26 @@ static inline int need_resched(void)
  */
 extern int _cond_resched(void);
 
-static inline int cond_resched(void)
-{
-	return _cond_resched();
-}
+#define cond_resched() ({			\
+	__might_sleep(__FILE__, __LINE__, 0);	\
+	_cond_resched();			\
+})
 
-extern int cond_resched_lock(spinlock_t * lock);
-extern int cond_resched_softirq(void);
-static inline int cond_resched_bkl(void)
-{
-	return _cond_resched();
-}
+extern int __cond_resched_lock(spinlock_t * lock);
+
+#define cond_resched_lock(lock) ({				\
+	__might_sleep(__FILE__, __LINE__, PREEMPT_OFFSET);	\
+	__cond_resched_lock(lock);				\
+})
+
+extern int __cond_resched_softirq(void);
+
+#define cond_resched_softirq() ({				\
+	__might_sleep(__FILE__, __LINE__, SOFTIRQ_OFFSET);	\
+	__cond_resched_softirq();				\
+})
+
+#define cond_resched_bkl()	cond_resched()
 
 /*
  * Does a critical section need to be broken due to another
diff --git a/kernel/sched.c b/kernel/sched.c
index 847e8fb..b9950b1 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6610,8 +6610,6 @@ static inline int should_resched(void)
 
 static void __cond_resched(void)
 {
-	__might_sleep(__FILE__, __LINE__, 0);
-
 	add_preempt_count(PREEMPT_ACTIVE);
 	schedule();
 	sub_preempt_count(PREEMPT_ACTIVE);
@@ -6628,14 +6626,14 @@ int __sched _cond_resched(void)
 EXPORT_SYMBOL(_cond_resched);
 
 /*
- * cond_resched_lock() - if a reschedule is pending, drop the given lock,
+ * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
  * call schedule, and on return reacquire the lock.
  *
  * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
  * operations here to prevent schedule() from being called twice (once via
  * spin_unlock(), once by hand).
  */
-int cond_resched_lock(spinlock_t *lock)
+int __cond_resched_lock(spinlock_t *lock)
 {
 	int resched = should_resched();
 	int ret = 0;
@@ -6651,9 +6649,9 @@ int cond_resched_lock(spinlock_t *lock)
 	}
 	return ret;
 }
-EXPORT_SYMBOL(cond_resched_lock);
+EXPORT_SYMBOL(__cond_resched_lock);
 
-int __sched cond_resched_softirq(void)
+int __sched __cond_resched_softirq(void)
 {
 	BUG_ON(!in_softirq());
 
@@ -6665,7 +6663,7 @@ int __sched cond_resched_softirq(void)
 	}
 	return 0;
 }
-EXPORT_SYMBOL(cond_resched_softirq);
+EXPORT_SYMBOL(__cond_resched_softirq);
 
 /**
  * yield - yield the current processor to other threads.
-- 
1.6.2.3

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