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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5B4EDCCD184 for ; Tue, 14 Oct 2025 09:45:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=R75CvrIgcbILYeZyEie2SvMudL4DW8xIUI8yCH+RsPE=; b=IBHyYWIXwNWjz41GIzU2Q6cdpC FnxcwOb/Y3WMgUg/8QPUBs/xx5x5Ge7fO4wWKPmHPq88EkX7oJkKwpGnkp8pUU6MpywJfsD8U0NuL a2L5Hzhfyo+rgCxgDSxRi2nopM5VdRTVW8SdV7EYeB4WWVfuv+GkufwCc+iCV2yIuZopTdiqgXjKJ YnCbZG8UPEdwPHuYYbS1FXR4jiToucdV2S4Z8kiEEQWA6+iUG/b9i61UUk4EN/SdP+C5iAViq849q uiBfSVLFrSHw+AVvlmGsTAaSGFz3kL+lRmx961iig34dXcaAhtQGc/0kxTXlIirRERuCD+DzXe0j8 VnFt8vZA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v8bam-0000000Fnsc-1TqI; Tue, 14 Oct 2025 09:45:16 +0000 Received: from mail-wm1-x32f.google.com ([2a00:1450:4864:20::32f]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1v8bah-0000000FnqM-1gXM for linux-arm-kernel@lists.infradead.org; Tue, 14 Oct 2025 09:45:14 +0000 Received: by mail-wm1-x32f.google.com with SMTP id 5b1f17b1804b1-46e5980471eso27629185e9.2 for ; Tue, 14 Oct 2025 02:45:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1760435108; x=1761039908; darn=lists.infradead.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=R75CvrIgcbILYeZyEie2SvMudL4DW8xIUI8yCH+RsPE=; b=G39EaML9Dd4StJhmuK1jG6s6TqT16jw53VJ8vQJ4Esiu2/1ipAQ5ZQaJt6bF1jXijS tJLk5HiPxDDB65m/GNtne1n9BVgNTm+x3h/BpQUucc9F7Awla2yqcCvWv+0tFeuJ1tUQ hvPIthXGRn2cB7HTS/2Rp+yAvai9isIeDEtlVVVR1biq23yUlG7BRIAKMNswGS2eRdYF cTxxp2NAcxK7EUbOJjV1CS1n0wIGJMXs9T+lGx68vVFelCg7dMYruFWMZTcmgqMIlmMH V23XE3HiRfrsz3IbKqJR8tZJoXIicIcHYNwNpsYmtsxfFGEgvfEuiBlLNP3V9sCnPJ47 LpRw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760435108; x=1761039908; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=R75CvrIgcbILYeZyEie2SvMudL4DW8xIUI8yCH+RsPE=; b=gG+jCD+TH4O/TX1ayYGaFp6UCNrwTV/xzhN0GjBS1UOiwmuG/qh0h0TzOdQ3+FQRqE 9j8Q0KKx+3sIfd2zzeQWeIGaTfOENQdYiQ50laDR+GrHnnKa+6EyJAmoArarNtIKQ/q0 r/bHWdgpmc0k+EvpIx++W0Idki0T4j7jpkR9oK5RazZDMeTB+wc0bDldixXawtOhBMRx x06L05dus+PLEBtNyxCDPkc0lLgETf0MmROPps4pHv77NnimvY8ReEjT5EE9Wtlnv22y yfQWmaCcTVTdAuX+l5NlZqWr1FjlCT8W5gStNFU7j3xK9H1C9ZMrYYG51aqzN2vVOmI1 sMCg== X-Forwarded-Encrypted: i=1; AJvYcCV1kSBv2azMxyBdVxcxKVQyVW+0PVkdoFkttLZI7bZtG56vlygHfbErgMU8p/aioQiypPF6jAJtfiN4Om6oBoWo@lists.infradead.org X-Gm-Message-State: AOJu0YzsXeGoM9OfVTigPAE9ApHPJxGeieL7blHZMsAgPKQwcKJ9zcI4 SupSnuBZ8UJcWlRXHufZfjaIAWrXx3ErlJ1bw/oAvqTBClKp3785s3s4h3sh+YFrXmI= X-Gm-Gg: ASbGncsp8ZPEtV0RCLl0Wa5HM88CBpaIHOtsUSWwr7FFDi2iN3k3Kkxa1HTZS6j1nRv 80cSvG8w34ZWD98nIdZtRDzjfaSfAAQOHt45Wm9iXKSRaFNnfUkQZgQhgzZwEiWmRHIOIQFs0XF vRdEl+OqDSz84sepy2754hHwiYyq7jO45xtO1Vmt6WGL80YW9wUORybW3H2yZCYJQucpXo1EJZl fAEGRL/Dfc7bhq+jRB91Q9yPJleawFfCK8YCC8dOYedvPlkEwolI+pM+qPvYLkeuBlnCTQxfJ4W 33B2LLsAcjT9/4TA1f/vx1ICUFp4x7E85B4f7osuIbNn9Xxtazzvw7lGhrq+gMQtgwgEl8ZCp1W DHQGGwri1CzVZ7/EPOI6l6tSSGXcQamnWaAyE3KddkJIZ/7sa3FbmiLwjfMLUSjI1MWQMvg== X-Google-Smtp-Source: AGHT+IFLMF/oRlSecQb1AgZUj9ViudEM8BAiQCOLkhiN8cHZAWDwJ7zBbTzbicn8TdmEii38ZLu7Sw== X-Received: by 2002:a05:600c:890d:b0:46e:32f7:98fc with SMTP id 5b1f17b1804b1-46fa9af3656mr132535685e9.21.1760435107774; Tue, 14 Oct 2025 02:45:07 -0700 (PDT) Received: from pathway.suse.cz (nat2.prg.suse.com. [195.250.132.146]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46fb489ad27sm230711415e9.15.2025.10.14.02.45.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Oct 2025 02:45:07 -0700 (PDT) Date: Tue, 14 Oct 2025 11:45:05 +0200 From: Petr Mladek To: Lance Yang Cc: lirongqing , wireguard@lists.zx2c4.com, linux-arm-kernel@lists.infradead.org, "Liam R . Howlett" , linux-doc@vger.kernel.org, David Hildenbrand , Randy Dunlap , Stanislav Fomichev , linux-aspeed@lists.ozlabs.org, Andrew Jeffery , Joel Stanley , Russell King , Lorenzo Stoakes , Shuah Khan , Steven Rostedt , Jonathan Corbet , Joel Granados , Andrew Morton , Phil Auld , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Masami Hiramatsu , Jakub Kicinski , Pawan Gupta , Simon Horman , Anshuman Khandual , Florian Westphal , netdev@vger.kernel.org, Kees Cook , Arnd Bergmann , "Paul E . McKenney" , Feng Tang , "Jason A . Donenfeld" Subject: Re: [PATCH][v3] hung_task: Panic after fixed number of hung tasks Message-ID: References: <20251012115035.2169-1-lirongqing@baidu.com> <588c1935-835f-4cab-9679-f31c1e903a9a@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <588c1935-835f-4cab-9679-f31c1e903a9a@linux.dev> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251014_024511_467871_5848DF8A X-CRM114-Status: GOOD ( 20.68 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue 2025-10-14 13:23:58, Lance Yang wrote: > Thanks for the patch! > > I noticed the implementation panics only when N tasks are detected > within a single scan, because total_hung_task is reset for each > check_hung_uninterruptible_tasks() run. Great catch! Does it make sense? Is is the intended behavior, please? > So some suggestions to align the documentation with the code's > behavior below :) > On 2025/10/12 19:50, lirongqing wrote: > > From: Li RongQing > > > > Currently, when 'hung_task_panic' is enabled, the kernel panics > > immediately upon detecting the first hung task. However, some hung > > tasks are transient and the system can recover, while others are > > persistent and may accumulate progressively. My understanding is that this patch wanted to do: + report even temporary stalls + panic only when the stall was much longer and likely persistent Which might make some sense. But the code does something else. > > --- a/kernel/hung_task.c > > +++ b/kernel/hung_task.c > > @@ -229,9 +232,11 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) > > */ > > sysctl_hung_task_detect_count++; > > + total_hung_task = sysctl_hung_task_detect_count - prev_detect_count; > > trace_sched_process_hang(t); > > - if (sysctl_hung_task_panic) { > > + if (sysctl_hung_task_panic && > > + (total_hung_task >= sysctl_hung_task_panic)) { > > console_verbose(); > > hung_task_show_lock = true; > > hung_task_call_panic = true; I would expect that this patch added another counter, similar to sysctl_hung_task_detect_count. It would be incremented only once per check when a hung task was detected. And it would be cleared (reset) when no hung task was found. Best Regards, Petr