hrtimer: Provide hrtimer_sleeper_start_expires()

hrtimer_sleepers will gain a scheduling class dependent treatment on
PREEMPT_RT. Create a wrapper around hrtimer_start_expires() to make that
possible.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/hrtimer.h

@@ -408,6 +408,9 @@ static inline void hrtimer_start_expires(struct hrtimer *timer,
 	hrtimer_start_range_ns(timer, soft, delta, mode);
 }
 
+void hrtimer_sleeper_start_expires(struct hrtimer_sleeper *sl,
+				   enum hrtimer_mode mode);
+
 static inline void hrtimer_restart(struct hrtimer *timer)
 {
 	hrtimer_start_expires(timer, HRTIMER_MODE_ABS);

kernel/time/hrtimer.c

@@ -1650,6 +1650,21 @@ static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer)
 	return HRTIMER_NORESTART;
 }
 
+/**
+ * hrtimer_sleeper_start_expires - Start a hrtimer sleeper timer
+ * @sl:		sleeper to be started
+ * @mode:	timer mode abs/rel
+ *
+ * Wrapper around hrtimer_start_expires() for hrtimer_sleeper based timers
+ * to allow PREEMPT_RT to tweak the delivery mode (soft/hardirq context)
+ */
+void hrtimer_sleeper_start_expires(struct hrtimer_sleeper *sl,
+				   enum hrtimer_mode mode)
+{
+	hrtimer_start_expires(&sl->timer, mode);
+}
+EXPORT_SYMBOL_GPL(hrtimer_sleeper_start_expires);
+
 static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
 				   clockid_t clock_id, enum hrtimer_mode mode)
 {
@@ -1698,7 +1713,7 @@ static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mod
 
 	do {
 		set_current_state(TASK_INTERRUPTIBLE);
-		hrtimer_start_expires(&t->timer, mode);
+		hrtimer_sleeper_start_expires(t, mode);
 
 		if (likely(t->task))
 			freezable_schedule();
@@ -1953,7 +1968,7 @@ schedule_hrtimeout_range_clock(ktime_t *expires, u64 delta,
 
 	hrtimer_init_sleeper_on_stack(&t, clock_id, mode);
 	hrtimer_set_expires_range_ns(&t.timer, *expires, delta);
-	hrtimer_start_expires(&t.timer, mode);
+	hrtimer_sleeper_start_expires(&t, mode);
 
 	if (likely(t.task))
 		schedule();