linux-kernel - Re: [PATCH net v2] net: usb: Remove disruptive netif_wake_queue in rtl8150_set

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Message-ID: <20250924113653.5dad5e50.michal.pecio@gmail.com>
Date: Wed, 24 Sep 2025 11:36:53 +0200
From: Michal Pecio <michal.pecio@...il.com>
To: viswanath <viswanathiyyappan@...il.com>
Cc: andrew@...n.ch, andrew+netdev@...n.ch, davem@...emloft.net,
 david.hunter.linux@...il.com, edumazet@...gle.com, kuba@...nel.org,
 linux-kernel-mentees@...ts.linux.dev, linux-kernel@...r.kernel.org,
 linux-usb@...r.kernel.org, netdev@...r.kernel.org, pabeni@...hat.com,
 petkan@...leusys.com, skhan@...uxfoundation.org,
 syzbot+78cae3f37c62ad092caa@...kaller.appspotmail.com
Subject: Re: [PATCH net v2] net: usb: Remove disruptive netif_wake_queue in
 rtl8150_set_multicast

On Wed, 24 Sep 2025 13:32:52 +0530, viswanath wrote:
> On Wed, 24 Sept 2025 at 13:17, Michal Pecio <michal.pecio@...il.com> wrote:
> >
> > It's not freeing which matters but URB completion in the USB subsystem.  
> 
> Does URB completion include both successful and failed completions? I
> decided to go with "free urb" because I wasn't sure of that.

I think yes, usually in USB-speak "completion" is when the URB is
finished for any reason, including error or unlink/cancellation.
"Free" could suggest usb_free_urb().

But I see your point. Maybe "finish execution" is less ambiguous?

> I wasn't sure how to describe the flow of execution in a multi threaded program.
> I will resubmit a v3 with this version of the execution flow

I think it's an irrelevant detail which CPU executed which function.
It could all happen sequentially on a single core and it's still the
same bug.

In fact, I just reproduced it with all CPUs offlined except one.