linux-kernel - Re: 2.6.23-rc7-mm1: r/o mounts joke with lockdep

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Message-Id: <1190651581.26982.230.camel@localhost>
Date:	Mon, 24 Sep 2007 09:33:00 -0700
From:	Dave Hansen <haveblue@...ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Alexey Dobriyan <adobriyan@...ru>, linux-kernel@...r.kernel.org
Subject: Re: 2.6.23-rc7-mm1: r/o mounts joke with lockdep

On Mon, 2007-09-24 at 09:26 -0700, Andrew Morton wrote:
> On Mon, 24 Sep 2007 13:51:05 +0400 Alexey Dobriyan <adobriyan@...ru> wrote:
> 
> > static void lock_and_coalesce_cpu_mnt_writer_counts(void)
> > {
> > 	int cpu;
> > 	struct mnt_writer *cpu_writer;
> > 
> > 	for_each_possible_cpu(cpu) {
> > 		cpu_writer = &per_cpu(mnt_writers, cpu);
> > 		spin_lock_nested(&cpu_writer->lock, 42);
> > 		                                   ^^^^
> > 
> > What the heck is going on?
> 
> that was some random 2:00AM hack by me to make the warnings go away.
> 
> > Given that MAX_LOCKDEP_SUBCLASSES is only 8,
> > this reliably turns off lockdep at boot.
> 
> that explains why it worked so well.

Arjan gave me some ideas on how to fix this more properly.  I'm trying
to reproduce it and working on a patch now.

-- Dave

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