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path: root/drivers/rtc
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Diffstat (limited to 'drivers/rtc')
-rw-r--r--drivers/rtc/interface.c56
1 files changed, 37 insertions, 19 deletions
diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index b6bf57f25cc9..a1ba2caa8308 100644
--- a/drivers/rtc/interface.c
+++ b/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 always cancel the timer here first, 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)
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);