<!DOCTYPE html><html><head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
Am 11.04.25 um 11:29 schrieb Philipp Stanner:<br>
<blockquote type="cite" cite="mid:d3dee321cd6b70d6ca98768fbcf6f1e6134c43a1.camel@mailbox.org">[SNIP]<span style="white-space: pre-wrap">
</span>
<pre class="moz-quote-pre" wrap="">It could be, however, that at the same moment nouveau_fence_signal() is
removing that entry, holding the appropriate lock.
So we have a race. Again.</pre>
</blockquote>
<br>
Ah, yes of course. If signaled is called with or without the lock is
actually undetermined.<br>
<br>
<blockquote type="cite" cite="mid:d3dee321cd6b70d6ca98768fbcf6f1e6134c43a1.camel@mailbox.org">
<pre class="moz-quote-pre" wrap="">You see, fixing things in Nouveau is difficult :)
It gets more difficult if you want to clean it up "properly", so it
conforms to rules such as those from dma_fence.
I have now provided two fixes that both work, but you are not satisfied
with from the dma_fence-maintainer's perspective. I understand that,
but please also understand that it's actually not my primary task to
work on Nouveau. I just have to fix this bug to move on with my
scheduler work.</pre>
</blockquote>
<br>
Well I'm happy with whatever solution as long as it works, but as
far as I can see the approach with the callback simply doesn't.<br>
<br>
You just can't drop the fence reference for the list from the
callback.<br>
<br>
<blockquote type="cite" cite="mid:d3dee321cd6b70d6ca98768fbcf6f1e6134c43a1.camel@mailbox.org">
<pre class="moz-quote-pre" wrap="">So if you have another idea, feel free to share it. But I'd like to
know how we can go on here.</pre>
</blockquote>
<br>
Well the fence code actually works, doesn't it? The problem is
rather that setting the error throws a warning because it doesn't
expect signaled fences on the pending list.<br>
<br>
Maybe we should fix that instead.<br>
<br>
<blockquote type="cite" cite="mid:d3dee321cd6b70d6ca98768fbcf6f1e6134c43a1.camel@mailbox.org">
<pre class="moz-quote-pre" wrap="">I'm running out of ideas. What I'm wondering if we couldn't just remove
performance hacky fastpath functions such as
nouveau_fence_is_signaled() completely. It seems redundant to me.</pre>
</blockquote>
<br>
That would work for me as well.<br>
<br>
<blockquote type="cite" cite="mid:d3dee321cd6b70d6ca98768fbcf6f1e6134c43a1.camel@mailbox.org">
<pre class="moz-quote-pre" wrap="">
Or we might add locking to it, but IDK what was achieved with RCU here.
In any case it's definitely bad that Nouveau has so many redundant and
half-redundant mechanisms.</pre>
</blockquote>
<br>
Yeah, agree messing with the locks even more won't help us here.<br>
<br>
Regards,<br>
Christian.<br>
<br>
<blockquote type="cite" cite="mid:d3dee321cd6b70d6ca98768fbcf6f1e6134c43a1.camel@mailbox.org">
<pre class="moz-quote-pre" wrap="">
P.
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">
P.
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">
Regards,
Christian.
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">
P.
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Regards,
Christian.
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">Replace the call to dma_fence_is_signaled() with
nouveau_fence_base_is_signaled().
Cc: <a class="moz-txt-link-rfc2396E" href="mailto:stable@vger.kernel.org"><stable@vger.kernel.org></a> # 4.10+, precise commit not to
be
determined
Signed-off-by: Philipp Stanner <a class="moz-txt-link-rfc2396E" href="mailto:phasta@kernel.org"><phasta@kernel.org></a>
---
drivers/gpu/drm/nouveau/nouveau_fence.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c
b/drivers/gpu/drm/nouveau/nouveau_fence.c
index 7cc84472cece..33535987d8ed 100644
--- a/drivers/gpu/drm/nouveau/nouveau_fence.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
@@ -274,7 +274,7 @@ nouveau_fence_done(struct nouveau_fence
*fence)
nvif_event_block(&fctx->event);
spin_unlock_irqrestore(&fctx->lock, flags);
}
- return dma_fence_is_signaled(&fence->base);
+ return test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence-
</pre>
<blockquote type="cite">
<pre class="moz-quote-pre" wrap="">base.flags);
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap=""> }
static long
</pre>
</blockquote>
</blockquote>
</blockquote>
</blockquote>
<pre class="moz-quote-pre" wrap="">
</pre>
</blockquote>
<pre class="moz-quote-pre" wrap="">
</pre>
</blockquote>
<br>
</body>
</html>