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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 6E53FC47096 for ; Thu, 3 Jun 2021 17:13:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 52173613F1 for ; Thu, 3 Jun 2021 17:13:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233079AbhFCROv (ORCPT ); Thu, 3 Jun 2021 13:14:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:43558 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232142AbhFCRLX (ORCPT ); Thu, 3 Jun 2021 13:11:23 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 98D9761403; Thu, 3 Jun 2021 17:09:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622740178; bh=iydd7/lLe2YBZgNs0P8XUJkIKV85aOB++zFFoo+tm/o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qkgsoIhnEkE0K4lqihR/HVg58HR9ytSgmKDtxQD2fI3bFBP2pCipQAl1mcCJ6jOhQ qLuNIsOgeiIr3lrbcH2UwEgX1gluIhUMJ54L3XtMiPLTQs/FqNadN0vOOiN4kEfni3 dEzlU1VcEGRRUWi+8LOrrmo+9l5WGzbv4MqCIR37MQnB9TVkIXkNEx8mJKrWMZP5CJ o0nMFn5Nh5GkxihguKYiACEdYxNyY4RK2AfYXzBWzL520kx6to+8kc9yJ/hXeymtc7 8vgZqNZaGQHoHmH4xVPI0+TROyBkMvl1f4UYJNx83Ne3p2CUtxjK2sN0mlUXt0s6s8 W1r6vsbtb6hlA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sergey Senozhatsky , Tejun Heo , Sasha Levin Subject: [PATCH AUTOSEL 5.4 15/31] wq: handle VM suspension in stall detection Date: Thu, 3 Jun 2021 13:09:03 -0400 Message-Id: <20210603170919.3169112-15-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210603170919.3169112-1-sashal@kernel.org> References: <20210603170919.3169112-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sergey Senozhatsky [ Upstream commit 940d71c6462e8151c78f28e4919aa8882ff2054e ] If VCPU is suspended (VM suspend) in wq_watchdog_timer_fn() then once this VCPU resumes it will see the new jiffies value, while it may take a while before IRQ detects PVCLOCK_GUEST_STOPPED on this VCPU and updates all the watchdogs via pvclock_touch_watchdogs(). There is a small chance of misreported WQ stalls in the meantime, because new jiffies is time_after() old 'ts + thresh'. wq_watchdog_timer_fn() { for_each_pool(pool, pi) { if (time_after(jiffies, ts + thresh)) { pr_emerg("BUG: workqueue lockup - pool"); } } } Save jiffies at the beginning of this function and use that value for stall detection. If VM gets suspended then we continue using "old" jiffies value and old WQ touch timestamps. If IRQ at some point restarts the stall detection cycle (pvclock_touch_watchdogs()) then old jiffies will always be before new 'ts + thresh'. Signed-off-by: Sergey Senozhatsky Signed-off-by: Tejun Heo Signed-off-by: Sasha Levin --- kernel/workqueue.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 5d7092e32912..8f41499d8257 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -50,6 +50,7 @@ #include #include #include +#include #include "workqueue_internal.h" @@ -5734,6 +5735,7 @@ static void wq_watchdog_timer_fn(struct timer_list *unused) { unsigned long thresh = READ_ONCE(wq_watchdog_thresh) * HZ; bool lockup_detected = false; + unsigned long now = jiffies; struct worker_pool *pool; int pi; @@ -5748,6 +5750,12 @@ static void wq_watchdog_timer_fn(struct timer_list *unused) if (list_empty(&pool->worklist)) continue; + /* + * If a virtual machine is stopped by the host it can look to + * the watchdog like a stall. + */ + kvm_check_and_clear_guest_paused(); + /* get the latest of pool and touched timestamps */ pool_ts = READ_ONCE(pool->watchdog_ts); touched = READ_ONCE(wq_watchdog_touched); @@ -5766,12 +5774,12 @@ static void wq_watchdog_timer_fn(struct timer_list *unused) } /* did we stall? */ - if (time_after(jiffies, ts + thresh)) { + if (time_after(now, ts + thresh)) { lockup_detected = true; pr_emerg("BUG: workqueue lockup - pool"); pr_cont_pool_info(pool); pr_cont(" stuck for %us!\n", - jiffies_to_msecs(jiffies - pool_ts) / 1000); + jiffies_to_msecs(now - pool_ts) / 1000); } } -- 2.30.2