From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756125Ab2BBM2U (ORCPT ); Thu, 2 Feb 2012 07:28:20 -0500 Received: from e06smtp18.uk.ibm.com ([195.75.94.114]:42028 "EHLO e06smtp18.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755735Ab2BBM2T (ORCPT ); Thu, 2 Feb 2012 07:28:19 -0500 Date: Thu, 2 Feb 2012 13:27:42 +0100 From: Heiko Carstens To: Frederic Weisbecker Cc: linux-kernel@vger.kernel.org, "Paul E. McKenney" , Ingo Molnar , Peter Zijlstra Subject: Re: rcu warnings cause stack overflow Message-ID: <20120202122742.GA2745@osiris.boeblingen.de.ibm.com> References: <20120201100652.GA2922@osiris.boeblingen.de.ibm.com> <20120201151445.GA6731@somewhere.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120201151445.GA6731@somewhere.redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) x-cbid: 12020212-6892-0000-0000-000000E3697E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.