drm/nouveau: fence: fix undefined fence state after emit

nouveau_fence_emit() can fail before and after initializing the
dma-fence and hence before and after initializing the dma-fence' kref.

In order to avoid nouveau_fence_emit() potentially failing before
dma-fence initialization pass the channel to nouveau_fence_new() already
and perform the required check before even allocating the fence.

While at it, restore the original behavior of nouveau_fence_new() and
add nouveau_fence_create() for separate (pre-)allocation instead. Always
splitting up allocation end emit wasn't a good idea in the first place.
Hence, limit it to the places where we actually need to pre-allocate.

Fixes: 7f2a0b50b2b2 ("drm/nouveau: fence: separate fence alloc and emit")
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230829223847.4406-1-dakr@redhat.com

1 files changed, 26 insertions, 6 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c b/drivers/gpu/drm/nouveau/nouveau_fence.c
index 77c739a55b19..61d9e70da9fd 100644
--- a/drivers/gpu/drm/nouveau/nouveau_fence.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
@@ -205,16 +205,13 @@ nouveau_fence_context_new(struct nouveau_channel *chan, struct nouveau_fence_cha
 }
 
 int
-nouveau_fence_emit(struct nouveau_fence *fence, struct nouveau_channel *chan)
+nouveau_fence_emit(struct nouveau_fence *fence)
 {
+	struct nouveau_channel *chan = fence->channel;
 	struct nouveau_fence_chan *fctx = chan->fence;
 	struct nouveau_fence_priv *priv = (void*)chan->drm->fence;
 	int ret;
 
-	if (unlikely(!chan->fence))
-		return -ENODEV;
-
-	fence->channel  = chan;
 	fence->timeout  = jiffies + (15 * HZ);
 
 	if (priv->uevent)
@@ -406,18 +403,41 @@ nouveau_fence_unref(struct nouveau_fence **pfence)
 }
 
 int
-nouveau_fence_new(struct nouveau_fence **pfence)
+nouveau_fence_create(struct nouveau_fence **pfence,
+		     struct nouveau_channel *chan)
 {
 	struct nouveau_fence *fence;
 
+	if (unlikely(!chan->fence))
+		return -ENODEV;
+
 	fence = kzalloc(sizeof(*fence), GFP_KERNEL);
 	if (!fence)
 		return -ENOMEM;
 
+	fence->channel = chan;
+
 	*pfence = fence;
 	return 0;
 }
 
+int
+nouveau_fence_new(struct nouveau_fence **pfence,
+		  struct nouveau_channel *chan)
+{
+	int ret = 0;
+
+	ret = nouveau_fence_create(pfence, chan);
+	if (ret)
+		return ret;
+
+	ret = nouveau_fence_emit(*pfence);
+	if (ret)
+		nouveau_fence_unref(pfence);
+
+	return ret;
+}
+
 static const char *nouveau_fence_get_get_driver_name(struct dma_fence *fence)
 {
 	return "nouveau";