Subject: sched: Take RT softirq semantics into account in cond_resched()
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 14 Jul 2011 09:56:44 +0200

The softirq semantics work different on -RT. There is no SOFTIRQ_MASK in
the preemption counter which leads to the BUG_ON() statement in
__cond_resched_softirq(). As for -RT it is enough to perform a "normal"
schedule.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/sched.h |    4 ++++
 kernel/sched/core.c   |    2 ++
 2 files changed, 6 insertions(+)

--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1519,12 +1519,16 @@ extern int __cond_resched_lock(spinlock_
 	__cond_resched_lock(lock);				\
 })
 
+#ifndef CONFIG_PREEMPT_RT_FULL
 extern int __cond_resched_softirq(void);
 
 #define cond_resched_softirq() ({					\
 	___might_sleep(__FILE__, __LINE__, SOFTIRQ_DISABLE_OFFSET);	\
 	__cond_resched_softirq();					\
 })
+#else
+# define cond_resched_softirq()		cond_resched()
+#endif
 
 static inline void cond_resched_rcu(void)
 {
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5095,6 +5095,7 @@ int __cond_resched_lock(spinlock_t *lock
 }
 EXPORT_SYMBOL(__cond_resched_lock);
 
+#ifndef CONFIG_PREEMPT_RT_FULL
 int __sched __cond_resched_softirq(void)
 {
 	BUG_ON(!in_softirq());
@@ -5108,6 +5109,7 @@ int __sched __cond_resched_softirq(void)
 	return 0;
 }
 EXPORT_SYMBOL(__cond_resched_softirq);
+#endif
 
 /**
  * yield - yield the current processor to other threads.