On Tue, Jul 22, 2025 at 9:22 AM Suchit K [off-list ref] wrote:

quoted

WRITE_ONCE() is missing.

Oops, I'm sorry about that.

quoted

quoted

+               while (i >= 0) {
+                       qdisc_change_tx_queue_len(dev, &dev->_tx[i]);

What happens if one of these calls fails ?

I think a fix will be more complicated...

I did consider that, but since I didn’t have a solution, I assumed it
wouldn’t fail.

But this definitely could fail. Exactly the same way than the first time.

I also have a question. In the Qdisc_ops structure,

there’s a function pointer for change_tx_queue_len, but I was only
able to find a single implementation which is
pfifo_fast_change_tx_queue_len. Is that the only one? Apologies if
this isn’t the right place to ask such questions. I’d really
appreciate any feedback. Thank you!

I think only pfifo_fast has to re-allocate its data structures.

Other qdiscs eventually dynamically read dev->tx_queue_len (thus the
WRITE_ONCE() I mentioned to you)