---

yaml
---
r: 260395
b: refs/heads/master
c: b830ac1
h: refs/heads/master
i:
  260393: 6337325
  260391: b48386d
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 431e2bcc371016824f419baa745f82388258f3ee
+refs/heads/master: b830ac1d9a2262093bb0f3f6a2fd2a1c8278daf5

trunk/drivers/rtc/interface.c

@@ -636,6 +636,29 @@ void rtc_irq_unregister(struct rtc_device *rtc, struct rtc_task *task)
 }
 EXPORT_SYMBOL_GPL(rtc_irq_unregister);
 
+static int rtc_update_hrtimer(struct rtc_device *rtc, int enabled)
+{
+	/*
+	 * We unconditionally cancel the timer here, because otherwise
+	 * we could run into BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
+	 * when we manage to start the timer before the callback
+	 * returns HRTIMER_RESTART.
+	 *
+	 * We cannot use hrtimer_cancel() here as a running callback
+	 * could be blocked on rtc->irq_task_lock and hrtimer_cancel()
+	 * would spin forever.
+	 */
+	if (hrtimer_try_to_cancel(&rtc->pie_timer) < 0)
+		return -1;
+
+	if (enabled) {
+		ktime_t period = ktime_set(0, NSEC_PER_SEC / rtc->irq_freq);
+
+		hrtimer_start(&rtc->pie_timer, period, HRTIMER_MODE_REL);
+	}
+	return 0;
+}
+
 /**
  * rtc_irq_set_state - enable/disable 2^N Hz periodic IRQs
  * @rtc: the rtc device
@@ -651,24 +674,21 @@ int rtc_irq_set_state(struct rtc_device *rtc, struct rtc_task *task, int enabled
 	int err = 0;
 	unsigned long flags;
 
+retry:
 	spin_lock_irqsave(&rtc->irq_task_lock, flags);
 	if (rtc->irq_task != NULL && task == NULL)
 		err = -EBUSY;
 	if (rtc->irq_task != task)
 		err = -EACCES;
-	if (err)
-		goto out;
-
-	if (enabled) {
-		ktime_t period = ktime_set(0, NSEC_PER_SEC/rtc->irq_freq);
-		hrtimer_start(&rtc->pie_timer, period, HRTIMER_MODE_REL);
-	} else {
-		hrtimer_cancel(&rtc->pie_timer);
+	if (!err) {
+		if (rtc_update_hrtimer(rtc, enabled) < 0) {
+			spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
+			cpu_relax();
+			goto retry;
+		}
+		rtc->pie_enabled = enabled;
 	}
-	rtc->pie_enabled = enabled;
-out:
 	spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
-
 	return err;
 }
 EXPORT_SYMBOL_GPL(rtc_irq_set_state);
@@ -690,20 +710,18 @@ int rtc_irq_set_freq(struct rtc_device *rtc, struct rtc_task *task, int freq)
 
 	if (freq <= 0 || freq > 5000)
 		return -EINVAL;
-
+retry:
 	spin_lock_irqsave(&rtc->irq_task_lock, flags);
 	if (rtc->irq_task != NULL && task == NULL)
 		err = -EBUSY;
 	if (rtc->irq_task != task)
 		err = -EACCES;
-	if (err == 0) {
+	if (!err) {
 		rtc->irq_freq = freq;
-		if (rtc->pie_enabled) {
-			ktime_t period;
-			hrtimer_cancel(&rtc->pie_timer);
-			period = ktime_set(0, NSEC_PER_SEC/rtc->irq_freq);
-			hrtimer_start(&rtc->pie_timer, period,
-					HRTIMER_MODE_REL);
+		if (rtc->pie_enabled && rtc_update_hrtimer(rtc, 1) < 0) {
+			spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
+			cpu_relax();
+			goto retry;
 		}
 	}
 	spin_unlock_irqrestore(&rtc->irq_task_lock, flags);