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

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commit 9fc64667ee upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ben Skeggs
2017-05-11 17:03:05 +10:00
committed by Greg Kroah-Hartman
parent 16e10490d2
commit 6445a49a8c
1 changed files with 10 additions and 7 deletions
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17
drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c
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@@ -65,14 +65,17 @@ 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;