netdev - Re: [PATCH net-next v5 2/2] mctp i2c: MCTP I2C binding driver

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Message-ID: <20220215075816.4188df1e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Tue, 15 Feb 2022 07:58:16 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Matt Johnston <matt@...econstruct.com.au>
Cc:     Wolfram Sang <wsa@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jeremy Kerr <jk@...econstruct.com.au>,
        linux-i2c@...r.kernel.org, netdev@...r.kernel.org,
        Zev Weiss <zev@...ilderbeest.net>
Subject: Re: [PATCH net-next v5 2/2] mctp i2c: MCTP I2C binding driver

On Tue, 15 Feb 2022 18:01:25 +0800 Matt Johnston wrote:
> Thanks. I'll just make sure to kthread_stop() prior to calling unregister. It
> looks like the kthread needs to keep running when the interface is down to
> handle MCTP release timeouts which unlock the i2c bus, so can't use ndo_stop.
> 
> Similarly for the RX path, can I safely call netif_rx(skb) after unregister?
> It looks like in that case it should be OK, since enqueue_to_backlog() tests
> for netif_running() and just drops the packet. (It's running from the I2C
> slave irq so can't just use a mutex).

I wouldn't do it, using an object after it's unregistered is asking for
trouble. RPS seems to happily dereference skb->dev. It may or may not
work.