linux-kernel - Re: 4.4: INFO: rcu_sched self-detected stall on CPU

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Message-ID: <20160502205431.GA14983@kroah.com>
Date:	Mon, 2 May 2016 13:54:31 -0700
From:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To:	Steven Haigh <netwiz@....id.au>
Cc:	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	xen-devel <xen-devel@...ts.xenproject.org>,
	linux-kernel@...r.kernel.org
Subject: Re: 4.4: INFO: rcu_sched self-detected stall on CPU

On Wed, Mar 30, 2016 at 05:04:28AM +1100, Steven Haigh wrote:
> Greg, please see below - this is probably more for you...
> 
> On 03/29/2016 04:56 AM, Steven Haigh wrote:
> >
> > Interestingly enough, this just happened again - but on a different
> > virtual machine. I'm starting to wonder if this may have something to do
> > with the uptime of the machine - as the system that this seems to happen
> > to is always different.
> >
> > Destroying it and monitoring it again has so far come up blank.
> >
> > I've thrown the latest lot of kernel messages here:
> >      http://paste.fedoraproject.org/346802/59241532
> 
> So I just did a bit of digging via the almighty Google.
> 
> I started hunting for these lines, as they happen just before the stall:
> BUG: Bad rss-counter state mm:ffff88007b7db480 idx:2 val:-1
> BUG: Bad rss-counter state mm:ffff880079c638c0 idx:0 val:-1
> BUG: Bad rss-counter state mm:ffff880079c638c0 idx:2 val:-1
> 
> I stumbled across this post on the lkml:
>     http://marc.info/?l=linux-kernel&m=145141546409607
> 
> The patch attached seems to reference the following change in
> unmap_mapping_range in mm/memory.c:
> > -	struct zap_details details;
> > +	struct zap_details details = { };
> 
> When I browse the GIT tree for 4.4.6:
> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/mm/memory.c?id=refs/tags/v4.4.6
> 
> I see at line 2411:
> struct zap_details details;
> 
> Is this something that has been missed being merged into the 4.4 tree?
> I'll admit my kernel knowledge is not enough to understand what the code
> actually does - but the similarities here seem uncanny.

I'm sorry, I have no idea what you are asking me about here.  Did I miss
a patch that should be backported?  Did I backport something
incorrectly?

confused,

greg k-h