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

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Message-ID: <18440.1461208466@turing-police.cc.vt.edu>
Date:	Wed, 20 Apr 2016 23:14:26 -0400
From:	Valdis.Kletnieks@...edu
To:	unlisted-recipients:; (no To-header on input)
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	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 Fri, 15 Apr 2016 10:10:33 -0400, Valdis.Kletnieks@...edu said:
> 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 will
> > >     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.

Following up some more - next-20160420 seems to work just fine, even with
no sign in 'git log -- mm/slab.c' of the fix-patch....

I'm obviously having a very bad "things that go bump in the night" with
kernels lately - this makes 3 different "makes no sense" things I've posted
in the last 6 hours... :)

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