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

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 <>
parent 3733bd8b
......@@ -36,23 +36,29 @@ nvkm_timer_alarm_trigger(struct nvkm_timer *tmr)
unsigned long flags;
/* 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))
list_move_tail(&alarm->head, &exec);
/* 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))
/* 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))
spin_unlock_irqrestore(&tmr->lock, flags);
/* execute any pending alarm handlers */
/* Execute completed callbacks. */
list_for_each_entry_safe(alarm, atemp, &exec, head) {
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