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

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Message-ID: <20250923072809.1a58edaf@kernel.org>
Date: Tue, 23 Sep 2025 07:28:09 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Michal Pecio <michal.pecio@...il.com>
Cc: I Viswanath <viswanathiyyappan@...il.com>, andrew@...n.ch,
 andrew+netdev@...n.ch, davem@...emloft.net, david.hunter.linux@...il.com,
 edumazet@...gle.com, 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 Tue, 23 Sep 2025 09:47:11 +0200 Michal Pecio wrote:
> On Mon, 22 Sep 2025 18:07:42 -0700, Jakub Kicinski wrote:
> > On Sat, 20 Sep 2025 23:48:52 +0530 I Viswanath wrote:  
> > > rtl8150_set_multicast is rtl8150's implementation of ndo_set_rx_mode and
> > > should not be calling netif_stop_queue and notif_start_queue as these handle 
> > > TX queue synchronization.
> > > 
> > > The net core function dev_set_rx_mode handles the synchronization
> > > for rtl8150_set_multicast making it safe to remove these locks.    
> > 
> > Last time someone tried to add device ID to this driver was 20 years
> > ago. Please post a patch to delete this driver completely. If someone
> > speaks up we'll revert the removal and ask them to test the fix.  
> 
> These were quite common, I still have one.
> 
> What sort of testing do you need?

Excellent, could you check if there is any adverse effect of repeatedly
writing the RCR register under heavy Tx traffic (without stopping/waking
the Tx queue)? The driver seems to pause Tx when RCR is written, seems
like an odd thing to do without a reason, but driver authors do the
darndest things.