This is a note to let you know that I've just added the patch titled
drm/nouveau/tmr: handle races with hw when updating the next alarm time
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-nouveau-tmr-handle-races-with-hw-when-updating-the-next-alarm-time.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1b0f84380b10ee97f7d2dd191294de9017e94d1d Mon Sep 17 00:00:00 2001
From: Ben Skeggs <bskeggs@xxxxxxxxxx>
Date: Thu, 11 May 2017 17:19:48 +1000
Subject: drm/nouveau/tmr: handle races with hw when updating the next alarm time
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);
Patches currently in stable-queue which might be from bskeggs@xxxxxxxxxx are
queue-4.9/drm-nouveau-tmr-ack-interrupt-before-processing-alarms.patch
queue-4.9/drm-nouveau-tmr-fix-corruption-of-the-pending-list-when-rescheduling-an-alarm.patch
queue-4.9/drm-nouveau-tmr-avoid-processing-completed-alarms-when-adding-a-new-one.patch
queue-4.9/drm-nouveau-mmu-nv4a-use-nv04-mmu-rather-than-the-nv44-one.patch
queue-4.9/drm-nouveau-therm-remove-ineffective-workarounds-for-alarm-bugs.patch
queue-4.9/drm-nouveau-tmr-handle-races-with-hw-when-updating-the-next-alarm-time.patch