Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756940Ab1FGQye (ORCPT ); Tue, 7 Jun 2011 12:54:34 -0400 Received: from ch1ehsobe006.messaging.microsoft.com ([216.32.181.186]:51596 "EHLO CH1EHSOBE005.bigfish.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756836Ab1FGQyc (ORCPT ); Tue, 7 Jun 2011 12:54:32 -0400 X-SpamScore: 1 X-BigFish: VPS1(zzzz1202hzz8275bh8275dhz32i668h839h61h) X-Spam-TCS-SCL: 0:0 X-Forefront-Antispam-Report: CIP:163.181.249.108;KIP:(null);UIP:(null);IPVD:NLI;H:ausb3twp01.amd.com;RD:none;EFVD:NLI X-WSS-ID: 0LMFISR-01-1XX-02 X-M-MSG: From: Robert Richter To: Ingo Molnar CC: Peter Zijlstra , LKML , oprofile-list , Robert Richter , Suravee Suthikulpanit , Subject: [PATCH] oprofile, x86: Fix race in nmi handler while starting Date: Tue, 7 Jun 2011 18:47:29 +0200 Message-ID: <1307465249-20055-1-git-send-email-robert.richter@amd.com> X-Mailer: git-send-email 1.7.5.rc3 MIME-Version: 1.0 Content-Type: text/plain X-OriginatorOrg: amd.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2163 Lines: 71 In some rare cases, nmis are generated immediately after the nmi handler of the cpu was started. This causes the counter not to be enabled. Before enabling the nmi handlers we need to set variable ctr_running first and make sure its value is written to memory. Also, the patch makes all existing barriers a memory barrier instead of a compiler barrier only. Reported-by: Suravee Suthikulpanit Cc: # .35+ Signed-off-by: Robert Richter --- arch/x86/oprofile/nmi_int.c | 14 ++++++++++---- 1 files changed, 10 insertions(+), 4 deletions(-) diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c index cf97500..68894fd 100644 --- a/arch/x86/oprofile/nmi_int.c +++ b/arch/x86/oprofile/nmi_int.c @@ -112,8 +112,10 @@ static void nmi_cpu_start(void *dummy) static int nmi_start(void) { get_online_cpus(); - on_each_cpu(nmi_cpu_start, NULL, 1); ctr_running = 1; + /* make ctr_running visible to the nmi handler: */ + smp_mb(); + on_each_cpu(nmi_cpu_start, NULL, 1); put_online_cpus(); return 0; } @@ -504,15 +506,18 @@ static int nmi_setup(void) nmi_enabled = 0; ctr_running = 0; - barrier(); + /* make variables visible to the nmi handler: */ + smp_mb(); err = register_die_notifier(&profile_exceptions_nb); if (err) goto fail; get_online_cpus(); register_cpu_notifier(&oprofile_cpu_nb); - on_each_cpu(nmi_cpu_setup, NULL, 1); nmi_enabled = 1; + /* make nmi_enabled visible to the nmi handler: */ + smp_mb(); + on_each_cpu(nmi_cpu_setup, NULL, 1); put_online_cpus(); return 0; @@ -531,7 +536,8 @@ static void nmi_shutdown(void) nmi_enabled = 0; ctr_running = 0; put_online_cpus(); - barrier(); + /* make variables visible to the nmi handler: */ + smp_mb(); unregister_die_notifier(&profile_exceptions_nb); msrs = &get_cpu_var(cpu_msrs); model->shutdown(msrs); -- 1.7.5.rc3 -- 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/