drm/nouveau: Don't set signaled fences' error codes

Nouveau is mostly designed in a way that it's expected that fences only ever get signaled through nouveau_fence_signal(). However, in at least one other place, nouveau_fence_done(), can signal fences, too. If that happens (race) a signaled fence remains in the pending list for a while, until it gets removed by nouveau_fence_update().

Should nouveau_fence_context_kill() run in the meantime, this would be a bug because the function would attempt to set an error code on an already signaled fence.

Have nouveau_fence_context_kill() check for a fence being signaled.

Cc <[email protected]> # v5.10+

Fixes ea13e5abf807 ("drm/nouveau: signal pending fences when channel has been killed")

Suggested-by Christian König <[email protected]>

Signed-off-by Philipp Stanner <[email protected]>

nouveau_fence.c iterates over lists in a non-canonical way. Since the operations done are just basic for-each-loops, they should be written in the standard form.

Use for_each_safe() instead of the custom loop iterations.

Signed-off-by Philipp Stanner <[email protected]>

---
 drivers/gpu/drm/nouveau/nouveau_fence.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

drivers/gpu/drm/nouveau/nouveau_fence.c +6 -4

index 6ded8c2b6d3b..60d961b43488 100644
@@ -84,11 +84,12 @@ void
 nouveau_fence_context_kill(struct nouveau_fence_chan *fctx, int error)
 {
 	struct nouveau_fence *fence;
+	struct list_head *pos, *tmp;
 	unsigned long flags;
 
 	spin_lock_irqsave(&fctx->lock, flags);
-	while (!list_empty(&fctx->pending)) {
-		fence = list_entry(fctx->pending.next, typeof(*fence), head);
+	list_for_each_safe(pos, tmp, &fctx->pending) {
+		fence = list_entry(pos, struct nouveau_fence, head);
 
 		if (error && !dma_fence_is_signaled_locked(&fence->base))
 			dma_fence_set_error(&fence->base, error);

@@ -131,11 +132,12 @@ static int
 nouveau_fence_update(struct nouveau_channel *chan, struct nouveau_fence_chan *fctx)
 {
 	struct nouveau_fence *fence;
+	struct list_head *pos, *tmp;
 	int drop = 0;
 	u32 seq = fctx->read(chan);
 
-	while (!list_empty(&fctx->pending)) {
-		fence = list_entry(fctx->pending.next, typeof(*fence), head);
+	list_for_each_safe(pos, tmp, &fctx->pending) {
+		fence = list_entry(pos, struct nouveau_fence, head);
 
 		if ((int)(seq - fence->base.seqno) < 0)
 			break;

nouveau_fence.c iterates over lists in a non-canonical way. Since the operations done are just basic for-each-loops, they should be written in the standard form.

Use for_each_safe() instead of the custom loop iterations.