linux-kernel - Re: lockdep: BUG: MAX_LOCKDEP

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Message-ID: <20131219161045.GC25771@redhat.com>
Date:	Thu, 19 Dec 2013 11:10:45 -0500
From:	Dave Jones <davej@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: lockdep: BUG: MAX_LOCKDEP_ENTRIES too low!

On Thu, Dec 19, 2013 at 05:01:16PM +0100, Peter Zijlstra wrote:
 > On Thu, Dec 19, 2013 at 10:59:17AM -0500, Dave Jones wrote:
 > > On Thu, Dec 19, 2013 at 04:51:21PM +0100, Peter Zijlstra wrote:
 > >  > On Thu, Dec 19, 2013 at 10:39:57AM -0500, Sasha Levin wrote:
 > >  > > That discusses lockdep classes, which is actually fine in my case. I ran out of
 > >  > > MAX_LOCKDEP_ENTRIES, which isn't mentioned anywhere in Documentation/ .
 > >  > 
 > >  > Yeah, it suffers from the same problem though. Lockdep has static
 > >  > resource allocation and never frees them.
 > >  > 
 > >  > The lock classes are the smallest pool and usually run out first, but
 > >  > the same could happen for the entries, after all, the more classes we
 > >  > have the more class connections can happen.
 > >  > 
 > >  > Anyway, barring a leak and silly class mistakes like mentioned in the
 > >  > document there's nothing we can do except raise the number.
 > > 
 > > I tried this. When you bump it to 32k, it fares better but then you
 > > start seeing "BUG: MAX_LOCKDEP_CHAINS too low!" instead.
 > > I've not tried bumping that yet, as I've stopped seeing these lately
 > > due to hitting more serious bugs first.
 > 
 > What are you doing to trigger all this? I don't see these. Are you
 > loading/unloading modules a lot?

syscall fuzzing.

	Dave

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