Message-ID: <1479208023.2210.2.camel@suse.com>
Subject: Re: crash by cdc_acm driver in kernels 4.8-rc1/5
From: Oliver Neukum <oneukum@suse.com>
To: wim@djo.tudelft.nl
Cc: linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org
Date: Tue, 15 Nov 2016 12:07:03 +0100
In-Reply-To: <20161115001619.GA21030@djo.tudelft.nl>
References: <20160908115803.GA28274@djo.tudelft.nl>
         <1473337238.32073.2.camel@suse.com> <20160908125850.GC28274@djo.tudelft.nl>
         <1476713445.3938.1.camel@suse.com> <20161017152042.GA26559@djo.tudelft.nl>
         <1476793123.2637.3.camel@suse.com> <20161115001619.GA21030@djo.tudelft.nl>
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On Tue, 2016-11-15 at 01:16 +0100, Wim Osterholt wrote:

Hi,

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

OK. I haven't tested that, nor would I ever considered it.
 
> 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.

OK, something extremely strange is going on. And I think it is time to get
the big hammer out. I made an extremely stupid debugging patch. Could
you test with it?

	Regards
		Oliver


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