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Commit 1b0f8438 authored by Ben Skeggs's avatar Ben Skeggs
Browse files

drm/nouveau/tmr: handle races with hw when updating the next alarm time 



If the time to the next alarm is short enough, we could race with HW and
end up with an ~4 second delay until it triggers.

Fix this by checking again after we update HW.

Signed-off-by: default avatarBen Skeggs <bskeggs@redhat.com>
Cc: stable@vger.kernel.org
parent 3733bd8b

drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c

+16 −10
Original line number Diff line number Diff line
@@ -36,23 +36,29 @@ nvkm_timer_alarm_trigger(struct nvkm_timer *tmr) 
	unsigned long flags;

	LIST_HEAD(exec);



	/* move any due alarms off the pending list */

	/* Process pending alarms. */

	spin_lock_irqsave(&tmr->lock, flags);

	list_for_each_entry_safe(alarm, atemp, &tmr->alarms, head) {

		if (alarm->timestamp <= nvkm_timer_read(tmr))

		/* Have we hit the earliest alarm that hasn't gone off? */

		if (alarm->timestamp > nvkm_timer_read(tmr)) {

			/* Schedule it.  If we didn't race, we're done. */

			tmr->func->alarm_init(tmr, alarm->timestamp);

			if (alarm->timestamp > nvkm_timer_read(tmr))

				break;

		}



		/* Move to completed list.  We'll drop the lock before

		 * executing the callback so it can reschedule itself.

		 */

		list_move_tail(&alarm->head, &exec);

	}



	/* reschedule interrupt for next alarm time */

	if (!list_empty(&tmr->alarms)) {

		alarm = list_first_entry(&tmr->alarms, typeof(*alarm), head);

		tmr->func->alarm_init(tmr, alarm->timestamp);

	} else {

	/* Shut down interrupt if no more pending alarms. */

	if (list_empty(&tmr->alarms))

		tmr->func->alarm_fini(tmr);

	}

	spin_unlock_irqrestore(&tmr->lock, flags);



	/* execute any pending alarm handlers */

	/* Execute completed callbacks. */

	list_for_each_entry_safe(alarm, atemp, &exec, head) {

		list_del_init(&alarm->head);

		alarm->func(alarm);