Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752731AbYLZNof (ORCPT ); Fri, 26 Dec 2008 08:44:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751870AbYLZNo0 (ORCPT ); Fri, 26 Dec 2008 08:44:26 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:37931 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751621AbYLZNoY (ORCPT ); Fri, 26 Dec 2008 08:44:24 -0500 Date: Fri, 26 Dec 2008 14:42:18 +0100 From: Ingo Molnar To: Sam Ravnborg Cc: Yinghai Lu , David Howells , Kamalesh Babulal , Andrew Morton , Stephen Rothwell , linux-next@vger.kernel.org, LKML , mel@csn.ul.ie Subject: [PATCH] kbuild, sparseirq: work around GCC bug with __weak aliases Message-ID: <20081226134218.GA1054@elte.hu> References: <20081219134636.GA11772@linux.vnet.ibm.com> <494C0BF0.3080109@kernel.org> <20081223132127.GA5450@linux.vnet.ibm.com> <495153A4.5060201@kernel.org> <20081224163400.GA11562@linux.vnet.ibm.com> <49529CE1.4040005@kernel.org> <20081226091217.GA5100@linux.vnet.ibm.com> <4954AC7B.3020603@kernel.org> <20081226102716.GA31450@uranus.ravnborg.org> <20081226133354.GC29265@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081226133354.GC29265@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2309 Lines: 63 * Ingo Molnar wrote: > > I recall David Howells had a similar issue with the bootparamter patch > > set. The workaround he used was to add a barrier(); call in the weak > > function to avoid the inline. > > could we add some extra attribute to __weak that would have a similar > effect? Something like __attribute__((noinline)), or something silly > like __attribute__((deprecated)) - just to keep gcc from screwing up > __weak functions? Perhaps adding a section attribute would have a > similar effect? (putting weak definitions into an extra section is > probably helpful anyway) I've applied the patch below to tip/irq/sparseirq - could someone with an affected GCC version please check whether this solves the crash? Ingo -------------------> >From 0d41e654c877a0de441448ca2f63a72ed11c5d84 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Fri, 26 Dec 2008 14:39:51 +0100 Subject: [PATCH] kbuild, sparseirq: work around GCC bug with __weak aliases Impact: fix panic on null pointer with sparseirq Certain versions of GCC inline the weak global functions. Work it around by marking __weak functions as noinline. Signed-off-by: Ingo Molnar --- include/linux/compiler-gcc.h | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-) diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index 5c8351b..1ad72e6 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -41,11 +41,17 @@ #define __deprecated __attribute__((deprecated)) #define __packed __attribute__((packed)) -#define __weak __attribute__((weak)) #define __naked __attribute__((naked)) #define __noreturn __attribute__((noreturn)) /* + * Mark weak aliases also noinline, because some GCC versions + * incorrectly inline weak aliases (even when a non-weak variant + * is there) and thus cause crashes: + */ +#define __weak __attribute__((weak)) noinline + +/* * From the GCC manual: * * Many functions have no effects except the return value and their -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/