drm/nouveau/tmr: fix corruption of the pending list when rescheduling an alarm

[karo-tx-linux.git] / drivers / gpu / drm / nouveau / nvkm / subdev / timer / base.c

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c b/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
index 4e696627fdcdf3f47eb9de7e34fdb01b1ff722c2..d898787d514ca9ab83672793eeb227d43f272fdd 100644 (file)
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
@@ -71,14 +71,17 @@ nvkm_timer_alarm(struct nvkm_timer *tmr, u32 nsec, struct nvkm_alarm *alarm)
        struct nvkm_alarm *list;
        unsigned long flags;
 
-       alarm->timestamp = nvkm_timer_read(tmr) + nsec;
-
-       /* append new alarm to list, in soonest-alarm-first order */
+       /* Remove alarm from pending list.
+        *
+        * This both protects against the corruption of the list,
+        * and implements alarm rescheduling/cancellation.
+        */
        spin_lock_irqsave(&tmr->lock, flags);
-       if (!nsec) {
-               if (!list_empty(&alarm->head))
-                       list_del(&alarm->head);
-       } else {
+       list_del_init(&alarm->head);
+
+       if (nsec) {
+               /* Insert into pending list, ordered earliest to latest. */
+               alarm->timestamp = nvkm_timer_read(tmr) + nsec;
                list_for_each_entry(list, &tmr->alarms, head) {
                        if (list->timestamp > alarm->timestamp)
                                break;