linux-kernel - Re: lockdep: BUG: MAX_LOCKDEP

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Message-ID: <1387512333.4860.11.camel@marge.simpson.net>
Date:	Fri, 20 Dec 2013 05:05:33 +0100
From:	Mike Galbraith <bitbucket@...ine.de>
To:	Dave Jones <davej@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	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, 2013-12-19 at 10:59 -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.

I had the same problem while testdriving a 3.6-rt kernel with lots of
debug enabled.. had to double both ENTRIES/CHAINS to keep lockdep from
running away in a snit.

-Mike

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