netdev - Re: Requirements for a shutdown function?

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Message-ID: <f995d5b3-2a5c-df08-3915-f77ab9203844@codeaurora.org>
Date:   Tue, 9 May 2017 13:51:28 -0500
From:   Timur Tabi <timur@...eaurora.org>
To:     Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org
Subject: Re: Requirements for a shutdown function?

On 05/09/2017 01:46 PM, Florian Fainelli wrote:
> A good test case for exercising a .shutdown() function is kexec'ing a
> new kernel for instance.

I tried that.  I run iperf in one window while launching kexec in another.
Even without a shutdown function, network traffic appear to halt on its own
and the kexec succeeds.

Is it possible that the network stack detects a kexec and automatically
stops all network devices?

> You should put your HW in a state where it won't be doing DMA, or have
> any adverse side effects to the system, putting it in a low power state
> is also a good approach.

My in-house driver stops the RX and TX queues.  I'm guessing that's good
enough, but I don't have a failing test case to prove it.

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