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=-17.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 BFEC7C433B4 for ; Wed, 19 May 2021 17:54:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9697F61244 for ; Wed, 19 May 2021 17:54:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230104AbhESRzX (ORCPT ); Wed, 19 May 2021 13:55:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60094 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229638AbhESRzW (ORCPT ); Wed, 19 May 2021 13:55:22 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8ADDCC06175F for ; Wed, 19 May 2021 10:54:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: Content-Type:In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To: Subject:Sender:Reply-To:Content-ID:Content-Description; bh=X4Hjh8DAldf0KF0BZ3r+rJd5h6X3daTeunVEqLN2aOY=; b=VKu4j6ySattnmgf/ug/DKGTKGh VIPX6HQu4JFxcu7SCloAaxz9CIK5VSBfJnGrNuyJ+YmDNgChvw1lxbEY0tzVqQPcT8S4SbOV5Qsiz hprwBBPantKxBssxjagNMtX6l/yNRQNjcALvR1XrE5HUSPW6wGc2qdHtfjSTQQZji7HpRJYvcG10L M+65e/ZxPyWYwpMvT8hn4J25XTdxUftLbqpOR7myz6USDIkS4A3p62RipcE65LmR52Vuymk5XG1EB AONrxJ/nCKaNg1SuuO8pMNzWBiCpa2EYG5hBA1v4JX3/FX5FUHvOR6rfWvR3ivLE7NKQHBXWz99Fy +sEWbQZQ==; Received: from [2601:1c0:6280:3f0::7376] by bombadil.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1ljQOH-00Fftn-BA; Wed, 19 May 2021 17:53:53 +0000 Subject: Re: [PATCH] hungtask: add filter kthread/check comm To: chenguanyou , linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, keescook@chromium.org, mhocko@suse.com, lukas.bulwahn@gmail.com, vbabka@suse.cz, gpiccoli@canonical.com, chenguanyou References: <20210519121325.22083-1-chenguanyou@xiaomi.com> From: Randy Dunlap Message-ID: <26c6c7a7-4c85-7487-6dd6-1e66b41a2a27@infradead.org> Date: Wed, 19 May 2021 10:53:51 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <20210519121325.22083-1-chenguanyou@xiaomi.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Along with what Micahl has said, please see below. On 5/19/21 5:13 AM, chenguanyou wrote: > Some kernel threads are always in D state, when we enable hung_task, > it will misjudge, we should skip these to narrow the scope. > > exp mtk mobilephone: > root 420 420 2 0 0 kwdt_thread 0 D wdtk-0 > root 421 421 2 0 0 kwdt_thread 0 D wdtk-1 > root 422 422 2 0 0 kwdt_thread 0 D wdtk-2 > root 423 423 2 0 0 kwdt_thread 0 D wdtk-3 > root 424 424 2 0 0 kwdt_thread 0 D wdtk-4 > root 425 425 2 0 0 kwdt_thread 0 D wdtk-5 > root 426 426 2 0 0 kwdt_thread 0 D wdtk-6 > root 427 427 2 0 0 kwdt_thread 0 D wdtk-7 > root 435 435 2 0 0 mtk_lpm_monitor_thread 0 D LPM-0 > root 436 436 2 0 0 mtk_lpm_monitor_thread 0 D LPM-1 > root 437 437 2 0 0 mtk_lpm_monitor_thread 0 D LPM-2 > root 438 438 2 0 0 mtk_lpm_monitor_thread 0 D LPM-3 > root 439 439 2 0 0 mtk_lpm_monitor_thread 0 D LPM-4 > root 440 440 2 0 0 mtk_lpm_monitor_thread 0 D LPM-5 > root 441 441 2 0 0 mtk_lpm_monitor_thread 0 D LPM-6 > root 442 442 2 0 0 mtk_lpm_monitor_thread 0 D LPM-7 > > Signed-off-by: chenguanyou > --- > include/linux/sched/sysctl.h | 4 ++++ > kernel/hung_task.c | 17 +++++++++++++++++ > kernel/sysctl.c | 15 +++++++++++++++ > lib/Kconfig.debug | 23 +++++++++++++++++++++++ > 4 files changed, 59 insertions(+) > > diff --git a/kernel/hung_task.c b/kernel/hung_task.c > index 396ebaebea3f..e018563d4882 100644 > --- a/kernel/hung_task.c > +++ b/kernel/hung_task.c > @@ -23,6 +23,7 @@ > #include > > #include > +#include > > /* > * The number of tasks checked: > @@ -48,6 +49,16 @@ unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_ > */ > unsigned long __read_mostly sysctl_hung_task_check_interval_secs; > > +/* > + * Non zero means no checking kthread Non-zero > + */ > +unsigned int __read_mostly sysctl_hung_task_filter_kthread = CONFIG_DEFAULT_HUNG_TASK_FILTER_KTHREAD; > + > +/* > + * Only one > + */ > +char __read_mostly sysctl_hung_task_check_comm[TASK_COMM_LEN] = CONFIG_DEFAULT_HUNG_TASK_CHECK_COMM; > + > int __read_mostly sysctl_hung_task_warnings = 10; > > static int __read_mostly did_panic; > @@ -88,6 +99,12 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) > { > unsigned long switch_count = t->nvcsw + t->nivcsw; > > + if (unlikely(strlen(sysctl_hung_task_check_comm) && !strstr(t->comm, sysctl_hung_task_check_comm))) > + return; > + > + if (unlikely(sysctl_hung_task_filter_kthread && t->flags & PF_KTHREAD)) > + return; > + > /* > * Ensure the task is not frozen. > * Also, skip vfork and any other user process that freezer should skip. > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index 62fbd09b5dc1..157c47a8430a 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -2519,6 +2519,21 @@ static struct ctl_table kern_table[] = { > .proc_handler = proc_dointvec_minmax, > .extra1 = &neg_one, > }, > + { > + .procname = "hung_task_filter_kthread", > + .data = &sysctl_hung_task_filter_kthread, > + .maxlen = sizeof(int), > + .mode = 0644, > + .extra1 = SYSCTL_ZERO, > + .extra2 = SYSCTL_ONE, > + }, > + { > + .procname = "hung_task_check_comm", > + .data = &sysctl_hung_task_check_comm, > + .maxlen = TASK_COMM_LEN, > + .mode = 0644, > + .proc_handler = proc_dostring, > + }, > #endif These new sysctls should be documented in Documentation/admin-guide/sysctl/kernel.rst. > #ifdef CONFIG_RT_MUTEXES > { > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 2c7f46b366f1..59cfa9e230ee 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -1101,6 +1101,29 @@ config DEFAULT_HUNG_TASK_TIMEOUT > A timeout of 0 disables the check. The default is two minutes. > Keeping the default should be fine in most cases. > > +config DEFAULT_HUNG_TASK_FILTER_KTHREAD > + bool "Default filter kthread for hung task" > + depends on DETECT_HUNG_TASK > + default 0 > + help > + This option controls filter kthread used to determine when uses > + a kernel task has become "state=TASK_UNINTERRUPTIBLE" and should be skip. skipped. > + > + It can be adjusted at runtime via the kernel.hung_task_filter_kthread > + sysctl or by writing a value to > + /proc/sys/kernel/hung_task_filter_kthread. > + > + A filter of 1 disables the check check. > + > +config DEFAULT_HUNG_TASK_CHECK_COMM > + string "Default check only one comm" > + depends on DETECT_HUNG_TASK > + default "" > + help > + It can be adjusted at runtime via the kernel.hung_task_check_comm > + sysctl or by writing a value to > + /proc/sys/kernel/hung_task_check_comm. That help text doesn't tell how the Kconfig symbol is used. > + > config BOOTPARAM_HUNG_TASK_PANIC > bool "Panic (Reboot) On Hung Tasks" > depends on DETECT_HUNG_TASK > thanks. -- ~Randy