linux-kernel - Re: [PATCH v3] usb: gadget: u_ether: Use __netif_rx() in rx

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Message-ID: <20240917143618.jPgAwF3M@linutronix.de>
Date: Tue, 17 Sep 2024 16:36:18 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Hubert Wiśniewski <hubert.wisniewski.25632@...il.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ferry Toth <ftoth@...londelft.nl>,
	Hardik Gajjar <hgajjar@...adit-jv.com>, Kees Cook <kees@...nel.org>,
	Justin Stitt <justinstitt@...gle.com>,
	Richard Acayan <mailingradian@...il.com>,
	Jeff Johnson <quic_jjohnson@...cinc.com>,
	"Ricardo B. Marliere" <ricardo@...liere.net>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Toke Høiland-Jørgensen <toke@...hat.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] usb: gadget: u_ether: Use __netif_rx() in
 rx_callback()

On 2024-09-17 15:56:33 [+0200], Hubert Wiśniewski wrote:
> netif_rx() now disables bottom halves, which causes the USB gadget to be
> unable to receive frames if the interface is not brought up quickly enough
> after being created by the driver (a bug confirmed on AM3352 SoC).
> 
> Replacing netif_rx() with __netif_rx() restores the old behavior and fixes
> the bug. This can be done since rx_callback() is called from the interrupt
> context.
> 
> Fixes: baebdf48c360 ("net: dev: Makes sure netif_rx() can be invoked in any context.")
> Cc: stable@...r.kernel.org
> Signed-off-by: Hubert Wiśniewski <hubert.wisniewski.25632@...il.com>

Now that I see v3, my v2 question stands.
This supposed only to disable BH if invoked from from non-interrupt.
hardirq and softirq should be good. A backtrace would be nice and further
explanation how this becomes a problem. Also lockdep should complain at
some point.

Sebastian