From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754730AbaKDQWj (ORCPT ); Tue, 4 Nov 2014 11:22:39 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56471 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754631AbaKDQUu (ORCPT ); Tue, 4 Nov 2014 11:20:50 -0500 From: Don Zickus To: Andrew Morton Cc: Ingo Molnar , LKML , uobergfe@redhat.com, Don Zickus Subject: [PATCH 6/9] watchdog: implement error handling for failure to set up hardware perf events Date: Tue, 4 Nov 2014 11:20:21 -0500 Message-Id: <1415118024-194247-7-git-send-email-dzickus@redhat.com> In-Reply-To: <1415118024-194247-1-git-send-email-dzickus@redhat.com> References: <1415118024-194247-1-git-send-email-dzickus@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ulrich Obergfell If watchdog_nmi_enable() fails to set up the hardware perf event of one CPU, the entire hard lockup detector is deemed unreliable. Hence, disable the hard lockup detector and shut down the hardware perf events on all CPUs. Signed-off-by: Ulrich Obergfell Signed-off-by: Don Zickus --- kernel/watchdog.c | 18 ++++++++++++++++++ 1 files changed, 18 insertions(+), 0 deletions(-) diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 2897a5e..86ba5e5 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -502,6 +502,15 @@ static void watchdog(unsigned int cpu) __this_cpu_write(soft_lockup_hrtimer_cnt, __this_cpu_read(hrtimer_interrupts)); __touch_watchdog(); + + /* + * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the + * failure path. Check for failures that can occur asynchronously - + * for example, when CPUs are on-lined - and shut down the hardware + * perf event on each CPU accordingly. + */ + if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) + watchdog_nmi_disable(cpu); } #ifdef CONFIG_HARDLOCKUP_DETECTOR @@ -552,6 +561,15 @@ handle_err: goto out_save; } + /* + * Disable the hard lockup detector if _any_ CPU fails to set up + * set up the hardware perf event. The watchdog() function checks + * the NMI_WATCHDOG_ENABLED bit periodically. + */ + smp_mb__before_atomic(); + clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled); + smp_mb__after_atomic(); + /* skip displaying the same error again */ if (cpu > 0 && (PTR_ERR(event) == cpu0_err)) return PTR_ERR(event); -- 1.7.1