From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756212Ab0CCVVG (ORCPT ); Wed, 3 Mar 2010 16:21:06 -0500 Received: from mx1.redhat.com ([209.132.183.28]:23735 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753188Ab0CCVU6 (ORCPT ); Wed, 3 Mar 2010 16:20:58 -0500 From: Masami Hiramatsu Subject: [PATCH -tip 2/2] x86: Issue at least one memory barrier in stop_machine_text_poke(). To: Ingo Molnar , lkml Cc: systemtap , DLE , Masami Hiramatsu , Mathieu Desnoyers , Ingo Molnar , Jason Baron Date: Wed, 03 Mar 2010 16:27:04 -0500 Message-ID: <20100303212703.25645.50986.stgit@localhost6.localdomain6> In-Reply-To: <20100303212656.25645.48466.stgit@localhost6.localdomain6> References: <20100303212656.25645.48466.stgit@localhost6.localdomain6> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Fix stop_machine_text_poke() to issue smp_mb() before exiting waiting loop. Also, use ACCESS_ONCE() to check a flag according to Mathieu's comment. Signed-off-by: Masami Hiramatsu Cc: Mathieu Desnoyers Cc: Ingo Molnar Cc: Jason Baron --- arch/x86/kernel/alternative.c | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 635e4f4..3236a11 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -596,9 +596,9 @@ static int __kprobes stop_machine_text_poke(void *data) smp_wmb(); /* Make sure other cpus see that this has run */ wrote_text = 1; } else { - while (!wrote_text) - smp_rmb(); - sync_core(); + while (!ACCESS_ONCE(wrote_text)) + cpu_relax(); + smp_mb(); /* Load wrote_text before following execution */ } flush_icache_range((unsigned long)tpp->addr, -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America), Inc. Software Solutions Division e-mail: mhiramat@redhat.com