linux-kernel - Re: [PATCH 1/3] Increase lockdep limits: MAX_STACK_TRACE

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Date:	Wed, 8 Jul 2009 13:22:48 -0400
From:	Dave Jones <davej@...hat.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Joao Correia <joaomiguelcorreia@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Américo Wang <xiyou.wangcong@...il.com>
Subject: Re: [PATCH 1/3] Increase lockdep limits: MAX_STACK_TRACE_ENTRIES

On Tue, Jul 07, 2009 at 05:55:01PM +0200, Peter Zijlstra wrote:
 > On Tue, 2009-07-07 at 16:50 +0100, Joao Correia wrote:
 > 
 > > >> Yes. Anything 2.6.31 forward triggers this immediatly during init
 > > >> process, at random places.
 > > >
 > > > Not on my machines it doesn't.. so I suspect its something weird in
 > > > your .config or maybe due to some hardware you have that I don't that
 > > > triggers different drivers or somesuch.
 > > 
 > > I am not the only one reporting this, and it happens, for example,
 > > with a stock .config from a Fedora 11 install.
 > > 
 > > It may, of course, be a funny driver interaction yes, but other than
 > > stripping the box piece by piece, how would one go about debugging
 > > this otherwise?
 > 
 > One thing to do is stare (or share) at the output
 > of /proc/lockdep_chains and see if there's some particularly large
 > chains in there, or many of the same name or something.

I don't see any long chains, just lots of them.
29065 lines on my box that's hitting MAX_STACK_TRACE_ENTRIES 

 > /proc/lockdep_stats might also be interesting, mine reads like:
 
 lock-classes:                         1518 [max: 8191]
 direct dependencies:                  7142 [max: 16384]
 indirect dependencies:               97905
 all direct dependencies:            753706
 dependency chains:                    6201 [max: 32768]
 dependency chain hlocks:             16665 [max: 163840]
 in-hardirq chains:                    1380
 in-softirq chains:                     589
 in-process chains:                    4232
 stack-trace entries:                262144 [max: 262144]
 combined max dependencies:      3449006070
 hardirq-safe locks:                   1008
 hardirq-unsafe locks:                  364
 softirq-safe locks:                    838
 softirq-unsafe locks:                  322
 irq-safe locks:                       1043
 irq-unsafe locks:                      364
 hardirq-read-safe locks:                 0
 hardirq-read-unsafe locks:              48
 softirq-read-safe locks:                 0
 softirq-read-unsafe locks:              48
 irq-read-safe locks:                     0
 irq-read-unsafe locks:                  48
 uncategorized locks:                   104
 unused locks:                            0
 max locking depth:                       9
 max recursion depth:                    10
 debug_locks:                             0


	Dave

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