sched/rt: Add schedule_preempt_disabled()

Add helper to get rid of the ever repeating:

    preempt_enable_no_resched();
    schedule();
    preempt_disable();

patterns.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-wxx7btox7coby6ifv5vzhzgp@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 13 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1a6398424fab..03dd224d0667 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -361,6 +361,7 @@ extern signed long schedule_timeout_interruptible(signed long timeout);
 extern signed long schedule_timeout_killable(signed long timeout);
 extern signed long schedule_timeout_uninterruptible(signed long timeout);
 asmlinkage void schedule(void);
+extern void schedule_preempt_disabled(void);
 extern int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner);
 
 struct nsproxy;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 91fe6a0e9098..73022395c00e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3246,6 +3246,18 @@ asmlinkage void __sched schedule(void)
 }
 EXPORT_SYMBOL(schedule);
 
+/**
+ * schedule_preempt_disabled - called with preemption disabled
+ *
+ * Returns with preemption disabled. Note: preempt_count must be 1
+ */
+void __sched schedule_preempt_disabled(void)
+{
+        preempt_enable_no_resched();
+        schedule();
+        preempt_disable();
+}
+
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
 
 static inline bool owner_running(struct mutex *lock, struct task_struct *owner)