4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ben Skeggs <bskeggs@xxxxxxxxxx>
commit 1b0f84380b10ee97f7d2dd191294de9017e94d1d upstream.
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: Ben Skeggs <bskeggs@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c | 26 ++++++++++++++---------
1 file changed, 16 insertions(+), 10 deletions(-)
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
@@ -36,23 +36,29 @@ nvkm_timer_alarm_trigger(struct nvkm_tim
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))
- 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))
+ 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);