linux-kernel - Re: rcu warnings cause stack overflow

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Date:	Thu, 2 Feb 2012 11:11:16 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: rcu warnings cause stack overflow

On Thu, Feb 02, 2012 at 03:52:20PM +0100, Frederic Weisbecker wrote:
> On Thu, Feb 02, 2012 at 01:27:42PM +0100, Heiko Carstens wrote:
> > On Wed, Feb 01, 2012 at 04:14:48PM +0100, Frederic Weisbecker wrote:
> > > > Removing the WARN_ON_ONCE will fix this and, if lockdep is turned on, still
> > > > will find illegal uses. But it won't work for lockdep off configs...
> > > > So we probably want something better than the patch below.
> > > 
> > > Ah ok. Hmm, but why are you using an exception to implement WARN_ON()
> > > in s390? Is it to have a whole new stack for the warning path in order
> > > to avoid stack overflow from the place that called the WARN_ON() ?
> > 
> > The reason was to reduce the code footprint of the WARN_ON() and also
> > be able to print the register contents at the time the warning happened.
> 
> Ah ok, makes sense.

So Frederic should push his anti-recursion patch, then?

							Thanx, Paul

> > All architectures which define __WARN_TAINT implement warnings with
> > exceptions. Currently that are parisc, powerpc, s390 and sh.
> > 
> 

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