Subject: sched: Do not account rcu_preempt_depth on RT in might_sleep()
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 07 Jun 2011 09:19:06 +0200

RT changes the rcu_preempt_depth semantics, so we cannot check for it
in might_sleep().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/rcupdate.h |    7 +++++++
 kernel/sched/core.c      |    2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -261,6 +261,11 @@ void synchronize_rcu(void);
  * types of kernel builds, the rcu_read_lock() nesting depth is unknowable.
  */
 #define rcu_preempt_depth() (current->rcu_read_lock_nesting)
+#ifndef CONFIG_PREEMPT_RT_FULL
+#define sched_rcu_preempt_depth()	rcu_preempt_depth()
+#else
+static inline int sched_rcu_preempt_depth(void) { return 0; }
+#endif
 
 #else /* #ifdef CONFIG_PREEMPT_RCU */
 
@@ -286,6 +291,8 @@ static inline int rcu_preempt_depth(void
 	return 0;
 }
 
+#define sched_rcu_preempt_depth()	rcu_preempt_depth()
+
 #endif /* #else #ifdef CONFIG_PREEMPT_RCU */
 
 /* Internal to kernel */
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6270,7 +6270,7 @@ void __init sched_init(void)
 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
 static inline int preempt_count_equals(int preempt_offset)
 {
-	int nested = preempt_count() + rcu_preempt_depth();
+	int nested = preempt_count() + sched_rcu_preempt_depth();
 
 	return (nested == preempt_offset);
 }