Patch "drm/nouveau/fifo/gf100-: protect channel preempt with subdev mutex" has been added to the 4.8-stable tree

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

drm/nouveau/fifo/gf100-: protect channel preempt with subdev mutex

to the 4.8-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-fifo-gf100-protect-channel-preempt-with-subdev-mutex.patch
and it can be found in the queue-4.8 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: Sat, 5 Nov 2016 14:33:14 +1000
Subject: drm/nouveau/fifo/gf100-: protect channel preempt with subdev mutex

From: Ben Skeggs <[email protected]>

commit b27add13f500469127afdf011dbcc9c649e16e54 upstream.

This avoids an issue that occurs when we're attempting to preempt multiple channels simultaneously. HW seems to ignore preempt requests while it's still processing a previous one, which, well, makes sense.

Fixes random "fifo: SCHED_ERROR 0d []" + GPCCS page faults during parallel piglit runs on (at least) GM107.

---
 drivers/gpu/drm/nouveau/nvkm/engine/fifo/gpfifogf100.c |    9 ++++++---
 drivers/gpu/drm/nouveau/nvkm/engine/fifo/gpfifogk104.c |    8 +++++---
 2 files changed, 11 insertions(+), 6 deletions(-)

@@ -60,6 +60,7 @@ gf100_fifo_gpfifo_engine_fini(struct nvk
 	struct nvkm_gpuobj *inst = chan->base.inst;
 	int ret = 0;
 
+	mutex_lock(&subdev->mutex);
 	nvkm_wr32(device, 0x002634, chan->base.chid);
 	if (nvkm_msec(device, 2000,
 		if (nvkm_rd32(device, 0x002634) == chan->base.chid)

@@ -67,10 +68,12 @@ gf100_fifo_gpfifo_engine_fini(struct nvk
 	) < 0) {
 		nvkm_error(subdev, "channel %d [%s] kick timeout\n",
 			   chan->base.chid, chan->base.object.client->name);
-		ret = -EBUSY;
-		if (suspend)
-			return ret;
+		ret = -ETIMEDOUT;
 	}
+	mutex_unlock(&subdev->mutex);
+
+	if (ret && suspend)
+		return ret;
 
 	if (offset) {
 		nvkm_kmap(inst);

@@ -40,7 +40,9 @@ gk104_fifo_gpfifo_kick(struct gk104_fifo
 	struct nvkm_subdev *subdev = &fifo->base.engine.subdev;
 	struct nvkm_device *device = subdev->device;
 	struct nvkm_client *client = chan->base.object.client;
+	int ret = 0;
 
+	mutex_lock(&subdev->mutex);
 	nvkm_wr32(device, 0x002634, chan->base.chid);
 	if (nvkm_msec(device, 2000,
 		if (!(nvkm_rd32(device, 0x002634) & 0x00100000))

@@ -48,10 +50,10 @@ gk104_fifo_gpfifo_kick(struct gk104_fifo
 	) < 0) {
 		nvkm_error(subdev, "channel %d [%s] kick timeout\n",
 			   chan->base.chid, client->name);
-		return -EBUSY;
+		ret = -ETIMEDOUT;
 	}
-
-	return 0;
+	mutex_unlock(&subdev->mutex);
+	return ret;
 }
 
 static u32

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

queue-4.8/drm-nouveau-ttm-wait-for-bo-fence-to-signal-before-unmapping-vmas.patch queue-4.8/drm-nouveau-bios-require-checksum-to-match-for-fast-acpi-shadow-method.patch queue-4.8/drm-nouveau-gr-fallback-to-legacy-paths-during-firmware-lookup.patch queue-4.8/drm-nouveau-kms-lvds-panel-strap-moved-again-on-maxwell.patch queue-4.8/drm-nouveau-ltc-protect-clearing-of-comptags-with-mutex.patch queue-4.8/drm-nouveau-fifo-gf100-protect-channel-preempt-with-subdev-mutex.patch queue-4.8/drm-nouveau-i2c-gk110b-gm10x-use-the-correct-implementation.patch