From 9fc64667ee48c9a25e7dca1a6bcb6906fec5bcc5 Mon Sep 17 00:00:00 2001
From: Ben Skeggs <bskeggs@redhat.com>
Date: Thu, 11 May 2017 17:03:05 +1000
Subject: [PATCH] drm/nouveau/tmr: fix corruption of the pending list when
rescheduling an alarm
At least therm/fantog "attempts" to work around this issue, which could
lead to corruption of the pending alarm list.
Fix it properly by not updating the timestamp without the lock held, or
trying to add an already pending alarm to the pending alarm list....
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Cc: stable@vger.kernel.org
---
.../gpu/drm/nouveau/nvkm/subdev/timer/base.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c b/drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
index 4e696627fdcdf..d898787d514ca 100644
--- 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;
--
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