linux-kernel - Re: iwlwifi getting stuck with current Linus' tree (646da63172)

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Date:	Thu, 23 Apr 2015 09:12:46 +0000
From:	"Grumbach, Emmanuel" <emmanuel.grumbach@...el.com>
To:	"jkosina@...e.cz" <jkosina@...e.cz>
CC:	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"ilw@...ux.intel.com" <ilw@...ux.intel.com>,
	"Berg, Johannes" <johannes.berg@...el.com>
Subject: Re: iwlwifi getting stuck with current Linus' tree (646da63172)

On Thu, 2015-04-23 at 10:15 +0200, Jiri Kosina wrote:
> On Thu, 23 Apr 2015, Grumbach, Emmanuel wrote:
> 
> > > I've been running current Linus' tree and have been getting system lockups 
> > > frequently. After a few "silent" lockups, I was able to obtain a dmesg 
> > > before the machine turned dead again (wifi stopped working shortly before 
> > > that).
> > > 
> > > Before starting to debug / bisect (last known good on this machine is 
> > > 4.0-rc6), I am attaching the dmesg in case someone already knows what the 
> > > issue is.
> > > 
> > 
> > I briefly went over the iwlwifi commits between 4.0-rc6 and linux/master
> > and couldn't find anything obvious.
> > Note that for the device you have, the commits that touch
> > drivers/net/wireless/iwlwifi/mvm are not relevant.
> > 
> > What you are seeing is that the PCI host is disconnecting the WiFi NIC
> > for some weird reason. It is not the first time I see that, but
> > unfortunately, I have never been able to debug this. I am personally not
> > a HW PCI expert and I couldn't reproduce either...
> > 
> > I am afraid I won't save you the time of the bisection, but I am not
> > entirely sure that bisecting the iwlwifi driver is enough to find the
> > commit that broke it. You may want to bisect the pci bus driver as well.
> 
> The problem is that I can't really reliably reproduce it; it happens 
> rather often, but not so often that I could be certainly sure that my 
> distinction of good and bad kernels would be accurate.
> 
> I will try it, but I expect the result to be bogus because of this, 
> unfortunately.
> 

I can understand. A few users reported that this bug occurred more
reliably when moving their system, although it seems very weird to me.

> > First question is: Are you sure that 4.0-rc6 was good?
> 
> Pretty much, yes. I've been running it for quite some time on this 
> machine without any issues. But after updating to current HEAD two days 
> ago, the issue triggered like 6 or 7 times already.
> 

Ok - I will try to look at the PCI commits there although I am not sure
I'll be able to make much sense of them...

> Thanks,
>