sched/rt: Do not submit new work when PI-blocked

When we are PI-blocked then we want to get things done ASAP.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-vw8et3445km5b8mpihf4trae@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/sched.h

@@ -2082,12 +2082,20 @@ extern unsigned int sysctl_sched_cfs_bandwidth_slice;
 extern int rt_mutex_getprio(struct task_struct *p);
 extern void rt_mutex_setprio(struct task_struct *p, int prio);
 extern void rt_mutex_adjust_pi(struct task_struct *p);
+static inline bool tsk_is_pi_blocked(struct task_struct *tsk)
+{
+	return tsk->pi_blocked_on != NULL;
+}
 #else
 static inline int rt_mutex_getprio(struct task_struct *p)
 {
 	return p->normal_prio;
 }
 # define rt_mutex_adjust_pi(p)		do { } while (0)
+static inline bool tsk_is_pi_blocked(struct task_struct *tsk)
+{
+	return false;
+}
 #endif
 
 extern bool yield_to(struct task_struct *p, bool preempt);

kernel/sched/core.c

@@ -3227,7 +3227,7 @@ static void __sched __schedule(void)
 
 static inline void sched_submit_work(struct task_struct *tsk)
 {
-	if (!tsk->state)
+	if (!tsk->state || tsk_is_pi_blocked(tsk))
 		return;
 	/*
 	 * If we are going to sleep and we have plugged IO queued,