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Date: Thu, 2 Feb 2012 13:27:42 +0100
From: Heiko Carstens <heiko.carstens@...ibm.com>
To: Frederic Weisbecker <fweisbec@...il.com>
Cc: linux-kernel@...r.kernel.org,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Ingo Molnar <mingo@...e.hu>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: rcu warnings cause stack overflow
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.
All architectures which define __WARN_TAINT implement warnings with
exceptions. Currently that are parisc, powerpc, s390 and sh.
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