Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752662AbdFTVeK (ORCPT ); Tue, 20 Jun 2017 17:34:10 -0400 Received: from mga09.intel.com ([134.134.136.24]:12512 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751798AbdFTVeI (ORCPT ); Tue, 20 Jun 2017 17:34:08 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.39,366,1493708400"; d="scan'208";a="1162771167" From: kan.liang@intel.com To: linux-kernel@vger.kernel.org Cc: dzickus@redhat.com, mingo@kernel.org, akpm@linux-foundation.org, babu.moger@oracle.com, atomlin@redhat.com, prarit@redhat.com, torvalds@linux-foundation.org, peterz@infradead.org, tglx@linutronix.de, eranian@google.com, acme@redhat.com, ak@linux.intel.com, Kan Liang , stable@vger.kernel.org Subject: [PATCH] kernel/watchdog: fix spurious hard lockups Date: Tue, 20 Jun 2017 14:33:09 -0700 Message-Id: <20170620213309.30051-1-kan.liang@intel.com> X-Mailer: git-send-email 2.11.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2090 Lines: 52 From: Kan Liang Some users reported spurious NMI watchdog timeouts. We now have more and more systems where the Turbo range is wide enough that the NMI watchdog expires faster than the soft watchdog timer that updates the interrupt tick the NMI watchdog relies on. This problem was originally added by commit 58687acba592 ("lockup_detector: Combine nmi_watchdog and softlockup detector"). Previously the NMI watchdog would always check jiffies, which were ticking fast enough. But now the backing is quite slow so the expire time becomes more sensitive. For mainline the right fix is to switch the NMI watchdog to reference cycles, which tick always at the same rate independent of turbo mode. But this is requires some complicated changes in perf, which are too difficult to backport. Since we need a stable fix too just increase the NMI watchdog rate here to avoid the spurious timeouts. This is not an ideal fix because a 3x as large Turbo range could still fail, but for now that's not likely. Signed-off-by: Kan Liang Cc: stable@vger.kernel.org Fixes: 58687acba592 ("lockup_detector: Combine nmi_watchdog and softlockup detector") --- The right fix for mainline can be found here. perf/x86/intel: enable CPU ref_cycles for GP counter perf/x86/intel, watchdog: Switch NMI watchdog to ref cycles on x86 https://patchwork.kernel.org/patch/9779087/ https://patchwork.kernel.org/patch/9779089/ kernel/watchdog_hld.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c index 54a427d1f344..0f7c6e758b82 100644 --- a/kernel/watchdog_hld.c +++ b/kernel/watchdog_hld.c @@ -164,7 +164,7 @@ int watchdog_nmi_enable(unsigned int cpu) firstcpu = 1; wd_attr = &wd_hw_attr; - wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); + wd_attr->sample_period = 3 * hw_nmi_get_sample_period(watchdog_thresh); /* Try to register using hardware perf events */ event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL); -- 2.11.0