linux-kernel - Re: combinatorial explosion in lockdep

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Message-Id: <20080728.155651.71572255.davem@davemloft.net>
Date:	Mon, 28 Jul 2008 15:56:51 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	jeremy@...p.org
Cc:	mingo@...e.hu, peterz@...radead.org, linux-kernel@...r.kernel.org,
	rusty@...tcorp.com.au
Subject: Re: combinatorial explosion in lockdep

From: Jeremy Fitzhardinge <jeremy@...p.org>
Date: Mon, 28 Jul 2008 15:50:04 -0700

> David Miller wrote:
> > The triggering event seems to be kstopmachine as done by the first
> > module load.  This seems to create the situation where we do double RQ
> > locking on essentially all the run queues, in order to move the
> > kstopmachine threads around to their proprer cpus.  I think this is
> > what starts to make the lockdep dependency chains huge.
> >   
> 
> Does Rusty's stop_machine rewrite which puts the threads on the correct 
> cpus to start with at least mitigate the symptoms?

I could check that, but it won't keep this from happening
and being triggerable by a trivial userland program setting
scheduler affinities.
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