Commit 2b478add authored by Francisco Jerez's avatar Francisco Jerez Committed by Ben Skeggs
Browse files

drm/nouveau: Avoid race in the interchannel sync code. 



It needs a "strong" channel reference because it actually writes to
the channel pushbuf, otherwise the corresponding FIFO context could
get kicked off in the middle of nouveau_fence_sync().

Signed-off-by: default avatarFrancisco Jerez <currojerez@riseup.net>
Signed-off-by: default avatarBen Skeggs <bskeggs@redhat.com>
parent 2a6789ae

drivers/gpu/drm/nouveau/nouveau_fence.c

+15 −9
Original line number Diff line number Diff line
@@ -128,7 +128,7 @@ nouveau_fence_new(struct nouveau_channel *chan, struct nouveau_fence **pfence, 
struct nouveau_channel *

nouveau_fence_channel(struct nouveau_fence *fence)

{

	return fence ? fence->channel : NULL;

	return fence ? nouveau_channel_get_unlocked(fence->channel) : NULL;

}



int
@@ -381,17 +381,18 @@ nouveau_fence_sync(struct nouveau_fence *fence, 
	struct nouveau_channel *chan = nouveau_fence_channel(fence);

	struct drm_device *dev = wchan->dev;

	struct nouveau_semaphore *sema;

	int ret;

	int ret = 0;



	if (likely(!fence || chan == wchan ||

	if (likely(!chan || chan == wchan ||

		   nouveau_fence_signalled(fence, NULL)))

		return 0;

		goto out;



	sema = alloc_semaphore(dev);

	if (!sema) {

		/* Early card or broken userspace, fall back to

		 * software sync. */

		return nouveau_fence_wait(fence, NULL, true, false);

		ret = nouveau_fence_wait(fence, NULL, true, false);

		goto out;

	}



	/* try to take chan's mutex, if we can't take it right away
@@ -399,20 +400,25 @@ nouveau_fence_sync(struct nouveau_fence *fence, 
	 * order issues

	 */

	if (!mutex_trylock(&chan->mutex)) {

		free_semaphore(&sema->ref);

		return nouveau_fence_wait(fence, NULL, true, false);

		ret = nouveau_fence_wait(fence, NULL, true, false);

		goto out_unref;

	}



	/* Make wchan wait until it gets signalled */

	ret = emit_semaphore(wchan, NV_SW_SEMAPHORE_ACQUIRE, sema);

	if (ret)

		goto out;

		goto out_unlock;



	/* Signal the semaphore from chan */

	ret = emit_semaphore(chan, NV_SW_SEMAPHORE_RELEASE, sema);



out_unlock:

	mutex_unlock(&chan->mutex);

out:

out_unref:

	kref_put(&sema->ref, free_semaphore);

out:

	if (chan)

		nouveau_channel_put_unlocked(&chan);

	return ret;

}