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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 DCD73C61CF0 for ; Thu, 13 Sep 2018 15:23:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9F19E20854 for ; Thu, 13 Sep 2018 15:23:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9F19E20854 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728552AbeIMUdK (ORCPT ); Thu, 13 Sep 2018 16:33:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59296 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726824AbeIMUdK (ORCPT ); Thu, 13 Sep 2018 16:33:10 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 38C13C02C01F; Thu, 13 Sep 2018 15:23:10 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.34.27.30]) by smtp.corp.redhat.com (Postfix) with SMTP id 0006D5C1B4; Thu, 13 Sep 2018 15:23:07 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 13 Sep 2018 17:23:09 +0200 (CEST) Date: Thu, 13 Sep 2018 17:23:07 +0200 From: Oleg Nesterov To: "Rafael J. Wysocki" Cc: Vitaly Kuznetsov , Linux Kernel Mailing List , Linux PM , "Rafael J. Wysocki" , Andrew Morton , Dmitry Vyukov , Paul McKenney Subject: Re: [PATCH RFC] kernel/hung_task.c: disable on suspend Message-ID: <20180913152307.GA31894@redhat.com> References: <20180912161119.2692-1-vkuznets@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Thu, 13 Sep 2018 15:23:10 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/13, Rafael J. Wysocki wrote: > > On Wed, Sep 12, 2018 at 6:11 PM Vitaly Kuznetsov wrote: > > > > It is possible to observe hung_task complaints when system goes to > > suspend-to-idle state: > > > > PM: Syncing filesystems ... done. > > Freezing user space processes ... (elapsed 0.001 seconds) done. > > OOM killer disabled. > > Freezing remaining freezable tasks ... (elapsed 0.002 seconds) done. > > sd 0:0:0:0: [sda] Synchronizing SCSI cache > > INFO: task bash:1569 blocked for more than 120 seconds. > > Not tainted 4.19.0-rc3_+ #687 > > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > bash D 0 1569 604 0x00000000 > > Call Trace: > > ? __schedule+0x1fe/0x7e0 > > schedule+0x28/0x80 > > suspend_devices_and_enter+0x4ac/0x750 > > pm_suspend+0x2c0/0x310 > > This actually is a good catch, but the problem is related to what > happens to the monotonic clock during suspend to idle. > > The clock issue needs to be addressed anyway IMO and then this problem > will go away automatically. I don't understand your discussion with Vitaly, but shouldn't we make khungtaskd thread freezable anyway? Oleg. --- x/kernel/hung_task.c +++ x/kernel/hung_task.c @@ -185,7 +185,7 @@ static void check_hung_uninterruptible_t hung_task_show_lock = false; rcu_read_lock(); for_each_process_thread(g, t) { - if (!max_count--) + if (!max_count-- || freezing(current)) goto unlock; if (!--batch_count) { batch_count = HUNG_TASK_BATCHING; @@ -249,6 +249,7 @@ static int watchdog(void *dummy) { unsigned long hung_last_checked = jiffies; + set_freezable(); set_user_nice(current, 0); for ( ; ; ) { @@ -266,7 +267,7 @@ static int watchdog(void *dummy) hung_last_checked = jiffies; continue; } - schedule_timeout_interruptible(t); + freezable_schedule_timeout_interruptible(t); } return 0;