netdev - Re: [PATCH net v2 1/1] mlxbf_gige: Fix kernel panic at shutdown

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Message-ID: <20230612131707.GS12152@unreal>
Date: Mon, 12 Jun 2023 16:17:07 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Vladimir Oltean <olteanv@...il.com>
Cc: Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
	Asmaa Mnebhi <asmaa@...dia.com>, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	netdev@...r.kernel.org, cai.huoqing@...ux.dev, brgl@...ev.pl,
	chenhao288@...ilicon.com, huangguangbin2@...wei.com,
	David Thompson <davthompson@...dia.com>
Subject: Re: [PATCH net v2 1/1] mlxbf_gige: Fix kernel panic at shutdown

On Mon, Jun 12, 2023 at 03:37:18PM +0300, Vladimir Oltean wrote:
> On Mon, Jun 12, 2023 at 02:59:25PM +0300, Leon Romanovsky wrote:
> > As far as I can tell, the calls to .shutdown() and .remove() are
> > mutually exclusive.
> 
> In this particular case, or in general?
> 
> In general they aren't. If the owning bus driver also implements its .shutdown()
> as .remove(), then it will call the .remove() method of all devices on that bus.
> That, after .shutdown() had already been called for those same children.

Can you please help me to see how? What is the call chain?

>From what I see callback to ->shutdown() iterates over all devices in
that bus and relevant bus will check that driver is bound prior to call
to driver callback. In both cases, the driver is removed and bus won't
call to already removed device.

If it does, it is arguably bug in bus logic, which needs to prevent such
scenario.

Thanks