Re: rcu warnings cause stack overflow

From: Heiko Carstens
Date: Thu Feb 02 2012 - 07:28:22 EST

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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