From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 79D23CA9EAF for ; Thu, 24 Oct 2019 11:49:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 45A8521655 for ; Thu, 24 Oct 2019 11:49:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2439362AbfJXLtt (ORCPT ); Thu, 24 Oct 2019 07:49:49 -0400 Received: from mx2.suse.de ([195.135.220.15]:50026 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726326AbfJXLtr (ORCPT ); Thu, 24 Oct 2019 07:49:47 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 376D2ABC7; Thu, 24 Oct 2019 11:49:46 +0000 (UTC) From: Petr Mladek To: Thomas Gleixner , Ingo Molnar , Peter Zijlstra Cc: Laurence Oberman , Vincent Whitchurch , Michal Hocko , linux-kernel@vger.kernel.org, Petr Mladek Subject: [PATCH 1/3] watchdog/softlockup: Remove obsolete check of last reported task Date: Thu, 24 Oct 2019 13:49:26 +0200 Message-Id: <20191024114928.15377-2-pmladek@suse.com> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20191024114928.15377-1-pmladek@suse.com> References: <20191024114928.15377-1-pmladek@suse.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The commit 9cf57731b63e37ed995 ("watchdog/softlockup: Replace "watchdog/%u" threads with cpu_stop_work") caused that the watchdog is reliably touched during a task switch. As a result the check for a unnoticed task switch is not longer needed. And the commit b1a8de1f534337b398c7778 ("softlockup: make detector be aware of task switch of processes hogging cpu") can be reverted. Signed-off-by: Petr Mladek --- kernel/watchdog.c | 18 +----------------- 1 file changed, 1 insertion(+), 17 deletions(-) diff --git a/kernel/watchdog.c b/kernel/watchdog.c index f41334ef0971..b7e2046380cf 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -174,7 +174,6 @@ static DEFINE_PER_CPU(bool, softlockup_touch_sync); static DEFINE_PER_CPU(bool, soft_watchdog_warn); static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts); static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt); -static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved); static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved); static unsigned long soft_lockup_nmi_warn; @@ -416,22 +415,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) return HRTIMER_RESTART; /* only warn once */ - if (__this_cpu_read(soft_watchdog_warn) == true) { - /* - * When multiple processes are causing softlockups the - * softlockup detector only warns on the first one - * because the code relies on a full quiet cycle to - * re-arm. The second process prevents the quiet cycle - * and never gets reported. Use task pointers to detect - * this. - */ - if (__this_cpu_read(softlockup_task_ptr_saved) != - current) { - __this_cpu_write(soft_watchdog_warn, false); - __touch_watchdog(); - } + if (__this_cpu_read(soft_watchdog_warn) == true) return HRTIMER_RESTART; - } if (softlockup_all_cpu_backtrace) { /* Prevent multiple soft-lockup reports if one cpu is already @@ -447,7 +432,6 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n", smp_processor_id(), duration, current->comm, task_pid_nr(current)); - __this_cpu_write(softlockup_task_ptr_saved, current); print_modules(); print_irqtrace_events(current); if (regs) -- 2.16.4