Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752558Ab1C1GhL (ORCPT ); Mon, 28 Mar 2011 02:37:11 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:60924 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752309Ab1C1GhK (ORCPT ); Mon, 28 Mar 2011 02:37:10 -0400 Date: Mon, 28 Mar 2011 08:36:56 +0200 From: Ingo Molnar To: Pekka Enberg Cc: Pekka Enberg , Christoph Lameter , Linus Torvalds , Eric Dumazet , Thomas Gleixner , akpm@linux-foundation.org, tj@kernel.org, npiggin@kernel.dk, rientjes@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] slub: Disable the lockless allocator Message-ID: <20110328063656.GA29462@elte.hu> References: <1301161507.2979.105.camel@edumazet-laptop> <4D9026C8.6060905@cs.helsinki.fi> <20110328061929.GA24328@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes 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: 2443 Lines: 70 * Pekka Enberg wrote: > On Mon, Mar 28, 2011 at 9:19 AM, Ingo Molnar wrote: > >> Tejun, does this look good to you as well? I think it should go > >> through the percpu tree. It's needed to fix a boot crash with > >> lockless SLUB fastpaths enabled. > > > > AFAICS Linus applied it already: > > > > d7c3f8cee81f: percpu: Omit segment prefix in the UP case for cmpxchg_double > > Oh, I missed that. Did you test the patch, Ingo? It's missing attributions > and reference to the LKML discussion unfortunately... I think we might still be missing the hunk below - or is it now not needed anymore? Thanks, Ingo --------------> >From 53c0eceb7bf64f2a89c59ae4f14a676fa4128462 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Sat, 26 Mar 2011 14:49:56 -0500 Subject: [PATCH] per_cpu: Fix cmpxchg_double() for !SMP cmpxchg_double() should only be provided for SMP. In the UP case the GS register is not defined and the function will fail. Signed-off-by: Christoph Lameter Cc: Pekka Enberg Cc: torvalds@linux-foundation.org Cc: tj@kernel.org Cc: npiggin@kernel.dk Cc: rientjes@google.com Cc: linux-mm@kvack.org Cc: Eric Dumazet LKML-Reference: Signed-off-by: Ingo Molnar --- arch/x86/include/asm/percpu.h | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h index a09e1f0..52330a4 100644 --- a/arch/x86/include/asm/percpu.h +++ b/arch/x86/include/asm/percpu.h @@ -507,6 +507,7 @@ do { \ * it in software. The address used in the cmpxchg16 instruction must be * aligned to a 16 byte boundary. */ +#ifdef CONFIG_SMP #define percpu_cmpxchg16b_double(pcp1, o1, o2, n1, n2) \ ({ \ char __ret; \ @@ -529,6 +530,7 @@ do { \ #define irqsafe_cpu_cmpxchg_double_8(pcp1, pcp2, o1, o2, n1, n2) percpu_cmpxchg16b_double(pcp1, o1, o2, n1, n2) #endif +#endif /* This is not atomic against other CPUs -- CPU preemption needs to be off */ #define x86_test_and_clear_bit_percpu(bit, var) \ -- 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/