linux-kernel - Re: crash by cdc_acm driver in kernels 4.8-rc1/5

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Message-ID: <20161115001619.GA21030@djo.tudelft.nl>
Date:   Tue, 15 Nov 2016 01:16:19 +0100
From:   Wim Osterholt <wim@....tudelft.nl>
To:     Oliver Neukum <oneukum@...e.com>
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        Wim Osterholt <wim@....tudelft.nl>
Subject: Re: crash by cdc_acm driver in kernels 4.8-rc1/5

On Tue, Oct 18, 2016 at 02:18:43PM +0200, Oliver Neukum wrote:

> It definitely does not crash and is probed and your .config is not
> extremely unusual.

Hmmm.

> ... Something odd is going on.

Whell, yes.
The only thing that appears you'll have to do is unset 'CONFIG_SMP'.

My machines didn't have the luxury of multicore processors (until recently),
so there never has been any reason to deliberately switch these options on!

In the process of searching, many options may have changed. The crash/OOPS
has now mitigated into just a WARNING with a call trace.
(Or it could be a totally different bug?)
After the call trace the device is working normally and a shutdown
completes to the end now.
That is with the config given here:
http://webserver.djo.tudelft.nl/.config-4.9-rc4.OK (CONFIG_SMP=y)
http://webserver.djo.tudelft.nl/WARNING-4.9-rc4    (call trace for C_S unset)

Tests on other machines with (slightly) different configs all seem to
confirm that the problems are gone when CONFIG_SMP is set.

Regards, Wim.