From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756422Ab2GYICi (ORCPT ); Wed, 25 Jul 2012 04:02:38 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:45841 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754712Ab2GYICe (ORCPT ); Wed, 25 Jul 2012 04:02:34 -0400 Message-ID: <1343203348.3139.16.camel@dabdike> Subject: Re: [PATCH] debug: Do not permit CONFIG_DEBUG_STACK_USAGE=y on IA64 or PARISC From: James Bottomley To: Ingo Molnar Cc: Tony Luck , linux-kernel@vger.kernel.org, Ingo Molnar , Helge Deller , linux-parisc@vger.kernel.org, linux-ia64@vger.kernel.org, Fengguang Wu Date: Wed, 25 Jul 2012 12:02:28 +0400 In-Reply-To: <20120725074501.GB27950@gmail.com> References: <4a613b26cc402fb3ed8130cd07a37e76f4c133ef.1342634029.git.tony.luck@intel.com> <20120725074501.GB27950@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2012-07-25 at 09:45 +0200, Ingo Molnar wrote: > * Tony Luck wrote: > > > The stack_not_used() function in assumes that stacks > > grow downwards. This is not true on IA64 or PARISC, so this function > > would walk off in the wrong direction and into the weeds. > > > > Found on IA64 because of a compilation failure with recursive dependencies > > on IA64_TASKSIZE and IA64_THREAD_INFO_SIZE. > > > > Fixing the code is possible, but should be combined with other > > infrastructure additions to set up the "canary" at the end of the stack. > > > > Reported-by: Fengguang Wu (failed allmodconfig build) > > Signed-off-by: Tony Luck > > --- > > lib/Kconfig.debug | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > index ff5bdee..4a18650 100644 > > --- a/lib/Kconfig.debug > > +++ b/lib/Kconfig.debug > > @@ -714,7 +714,7 @@ config STACKTRACE > > > > config DEBUG_STACK_USAGE > > bool "Stack utilization instrumentation" > > - depends on DEBUG_KERNEL > > + depends on DEBUG_KERNEL && !IA64 && !PARISC > > The modern way of doing this is by adding an ARCH_SUPPORTS_ > flag. That's a bit daft, isn't it? We'd have to add ARCH_SUPPORTS_ flags to about 25 separate architectures just to get it not supported on these two. Since the problem is an invalid assumption about how the stack grows, why not just condition it on that. We actually have a config option for this: CONFIG_STACK_GROWSUP. But for some reason ia64 doesn't define this, why not, Tony? It looks deliberate because you have replaced a lot of #ifdef CONFIG_STACK_GROWSUP with #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64) but not all of them. James