linux-kernel - Re: mm: BUG: Bad rss-counter state

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Date:	Wed, 22 Jan 2014 20:52:41 -0500
From:	Dave Jones <davej@...hat.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Sasha Levin <sasha.levin@...cle.com>, khlebnikov@...nvz.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: mm: BUG: Bad rss-counter state

On Wed, Jan 22, 2014 at 05:39:25PM -0800, David Rientjes wrote:
 
 > > While fuzzing with trinity running inside a KVM tools guest using latest -next
 > > kernel,
 > > I've stumbled on a "mm: BUG: Bad rss-counter state" error which was pretty
 > > non-obvious
 > > in the mix of the kernel spew (why?).
 > > 
 > 
 > It's not a fatal condition and there's only a few possible stack traces 
 > that could be emitted during the exit() path.  I don't see how we could 
 > make it more visible other than its log-level which is already KERN_ALERT.
 > 
 > > I've added a small BUG() after the printk() in check_mm(), and here's the full
 > > output:
 > > 
 > 
 > Worst place to add it :)  At line 562 of kernel/fork.c in linux-next 
 > you're going to hit BUG() when there may be other counters that are also 
 > bad and they don't get printed.  
 > 
 > > [  318.334905] BUG: Bad rss-counter state mm:ffff8801e6dec000 idx:0 val:1
 > 
 > So our mm has a non-zero MM_FILEPAGES count, but there's nothing that was 
 > cited that would tell us what that is so there's not much to go on, unless 
 > someone already recognizes this as another issue.  Is this reproducible on 
 > 3.13 or only on linux-next?

Sasha, is this the current git tree version of Trinity ?
(I'm wondering if yesterdays munmap changes might be tickling this bug).

	Dave

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