linux-kernel - Re: linux-next crash during very early boot

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Message-ID: <58269.1460729433@turing-police.cc.vt.edu>
Date:	Fri, 15 Apr 2016 10:10:33 -0400
From:	Valdis.Kletnieks@...edu
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: linux-next crash during very early boot

On Thu, 14 Apr 2016 10:35:47 +0900, Joonsoo Kim said:
> On Wed, Apr 13, 2016 at 08:29:46PM -0400, Valdis Kletnieks wrote:
> > I'm seeing my laptop crash/wedge up/something during very early
> > boot - before it can write anything to the console.  Nothing in pstore,
> > need to hold down the power button for 6 seconds and reboot.
> >
> > git bisect points at:
> >
> > commit 7a6bacb133752beacb76775797fd550417e9d3a2
> > Author: Joonsoo Kim <iamjoonsoo.kim@....com>
> > Date:   Thu Apr 7 13:59:39 2016 +1000
> >
> >     mm/slab: factor out kmem_cache_node initialization code
> >
> >     It can be reused on other place, so factor out it.  Following patch wil
l
> >     use it.
> >
> >
> > Not sure what the problem is - the logic *looks* ok at first read.  The
> > patch *does* remove a spin_lock_irq() - but I find it difficult to
> > believe that with it gone, my laptop is able to hit the race condition
> > the spinlock protects against *every single boot*.
> >
> > The only other thing I see is that n->free_limit used to be assigned
> > every time, and now it's only assigned at initial creation.
>
> Hello,
>
> My fault. It should be assgined every time. Please test below patch.
> I will send it with proper SOB after you confirm the problem disappear.
> Thanks for report and analysis!

Following up - I verified that it was your patch series and not a bad bisect
by starting with a clean next-20160413 and reverting that series - and the
resulting kernel boots fine.

Will take a closer look at your fix patch and figure out what's still changed
afterwards - there's obviously some small semantic change that actually
matters, but we're not spotting it yet...

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