[PATCH] rtc class locking bugfixes

I got a lockdep warning when running "rtctest" so I though it'd be good
to see what was up.

- The warning was for rtc->irq_task_lock, gotten from rtc_update_irq()
by irq handlerss ... but in a handful of other cases, grabbed without
blocking IRQs.

- Some callers to rtc_update_irq() were not ensuring IRQs were blocked,
yet the routine expects that; make sure all callers block IRQs.

It would appear that RTC API tests haven't been part of anyone's kernel
regression test suite recently, at least not with lockdep running.

Signed-off-by: David Brownell <[e-mail]>
Acked-by: Alessandro Zummo <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/rtc/interface.c

···
 }
 EXPORT_SYMBOL_GPL(rtc_set_alarm);
 
+/**
+ * rtc_update_irq - report RTC periodic, alarm, and/or update irqs
+ * @class_dev: the rtc's class device
+ * @num: how many irqs are being reported (usually one)
+ * @events: mask of RTC_IRQF with one or more of RTC_PF, RTC_AF, RTC_UF
+ * Context: in_interrupt(), irqs blocked
+ */
 void rtc_update_irq(struct class_device *class_dev,
 		unsigned long num, unsigned long events)
 {
···
 	if (task == NULL || task->func == NULL)
 		return -EINVAL;
 
-	spin_lock(&rtc->irq_task_lock);
+	spin_lock_irq(&rtc->irq_task_lock);
 	if (rtc->irq_task == NULL) {
 		rtc->irq_task = task;
 		retval = 0;
 	}
-	spin_unlock(&rtc->irq_task_lock);
+	spin_unlock_irq(&rtc->irq_task_lock);
 
 	return retval;
 }
···
 {
 	struct rtc_device *rtc = to_rtc_device(class_dev);
 
-	spin_lock(&rtc->irq_task_lock);
+	spin_lock_irq(&rtc->irq_task_lock);
 	if (rtc->irq_task == task)
 		rtc->irq_task = NULL;
-	spin_unlock(&rtc->irq_task_lock);
+	spin_unlock_irq(&rtc->irq_task_lock);
 }
 EXPORT_SYMBOL_GPL(rtc_irq_unregister);
 

drivers/rtc/rtc-at91.c

···
 					AT91_RTC_CALEV);
 
 	ret = request_irq(AT91_ID_SYS, at91_rtc_interrupt,
-				IRQF_SHARED, "at91_rtc", pdev);
+				IRQF_DISABLED | IRQF_SHARED,
+				"at91_rtc", pdev);
 	if (ret) {
 		printk(KERN_ERR "at91_rtc: IRQ %d already in use.\n",
 				AT91_ID_SYS);

drivers/rtc/rtc-dev.c

···
 	int err;
 
 	err = rtc_read_time(&rtc->class_dev, &tm);
-	spin_lock_irq(&rtc->irq_lock);
+
+	local_irq_disable();
+	spin_lock(&rtc->irq_lock);
 	if (rtc->stop_uie_polling || err) {
 		rtc->uie_task_active = 0;
 	} else if (rtc->oldsecs != tm.tm_sec) {
···
 	} else if (schedule_work(&rtc->uie_task) == 0) {
 		rtc->uie_task_active = 0;
 	}
-	spin_unlock_irq(&rtc->irq_lock);
+	spin_unlock(&rtc->irq_lock);
 	if (num)
 		rtc_update_irq(&rtc->class_dev, num, RTC_UF | RTC_IRQF);
+	local_irq_enable();
 }
-
 static void rtc_uie_timer(unsigned long data)
 {
 	struct rtc_device *rtc = (struct rtc_device *)data;
···
 
 	/* avoid conflicting IRQ users */
 	if (cmd == RTC_PIE_ON || cmd == RTC_PIE_OFF || cmd == RTC_IRQP_SET) {
-		spin_lock(&rtc->irq_task_lock);
+		spin_lock_irq(&rtc->irq_task_lock);
 		if (rtc->irq_task)
 			err = -EBUSY;
-		spin_unlock(&rtc->irq_task_lock);
+		spin_unlock_irq(&rtc->irq_task_lock);
 
 		if (err < 0)
 			return err;

drivers/rtc/rtc-ds1553.c

···
 
 	if (pdata->irq >= 0) {
 		writeb(0, ioaddr + RTC_INTERRUPTS);
-		if (request_irq(pdata->irq, ds1553_rtc_interrupt, IRQF_SHARED,
+		if (request_irq(pdata->irq, ds1553_rtc_interrupt,
+				IRQF_DISABLED | IRQF_SHARED,
 				pdev->name, pdev) < 0) {
 			dev_warn(&pdev->dev, "interrupt not available.\n");
 			pdata->irq = -1;

drivers/rtc/rtc-test.c

···
 	struct rtc_device *rtc = platform_get_drvdata(plat_dev);
 
 	retval = count;
+	local_irq_disable();
 	if (strncmp(buf, "tick", 4) == 0)
 		rtc_update_irq(&rtc->class_dev, 1, RTC_PF | RTC_IRQF);
 	else if (strncmp(buf, "alarm", 5) == 0)
···
 		rtc_update_irq(&rtc->class_dev, 1, RTC_UF | RTC_IRQF);
 	else
 		retval = -EINVAL;
+	local_irq_enable();
 
 	return retval;
 }