Patch "drm/nouveau/tmr: fully separate alarm execution/pending lists" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

drm/nouveau/tmr: fully separate alarm execution/pending lists

to the 4.4-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-fully-separate-alarm-execution-pending-lists.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Ben Skeggs <[email protected]>
Date: Mon, 5 Jun 2017 17:23:32 +1000
Subject: drm/nouveau/tmr: fully separate alarm execution/pending lists

From: Ben Skeggs <[email protected]>

commit b4e382ca7586a63b6c1e5221ce0863ff867c2df6 upstream.

Reusing the list_head for both is a bad idea. Callback execution is done with the lock dropped so that alarms can be rescheduled from the callback, which means that with some unfortunate timing, lists can get corrupted.

The execution list should not require its own locking, the single function that uses it can only be called from a single context.

---
 drivers/gpu/drm/nouveau/include/nvkm/subdev/timer.h |    1 +
 drivers/gpu/drm/nouveau/nvkm/subdev/timer/base.c    |    7 ++++---
 2 files changed, 5 insertions(+), 3 deletions(-)

@@ -4,6 +4,7 @@
 
 struct nvkm_alarm {
 	struct list_head head;
+	struct list_head exec;
 	u64 timestamp;
 	void (*func)(struct nvkm_alarm *);
 };

@@ -50,7 +50,8 @@ nvkm_timer_alarm_trigger(struct nvkm_tim
 		/* Move to completed list.  We'll drop the lock before
 		 * executing the callback so it can reschedule itself.
 		 */
-		list_move_tail(&alarm->head, &exec);
+		list_del_init(&alarm->head);
+		list_add(&alarm->exec, &exec);
 	}
 
 	/* Shut down interrupt if no more pending alarms. */

@@ -59,8 +60,8 @@ nvkm_timer_alarm_trigger(struct nvkm_tim
 	spin_unlock_irqrestore(&tmr->lock, flags);
 
 	/* Execute completed callbacks. */
-	list_for_each_entry_safe(alarm, atemp, &exec, head) {
-		list_del_init(&alarm->head);
+	list_for_each_entry_safe(alarm, atemp, &exec, exec) {
+		list_del(&alarm->exec);
 		alarm->func(alarm);
 	}
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/drm-nouveau-tmr-fully-separate-alarm-execution-pending-lists.patch