From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-180.mta1.migadu.com (out-180.mta1.migadu.com [95.215.58.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0D05FE56A for ; Sun, 28 Sep 2025 03:29:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759030163; cv=none; b=gg+dgGngVbiAnstG4SKJZjy4VWN0+wC8OgSwkKRtO2rssHi5/zJkHR/g2bkzYcheynSRWvw/3ZI6wJ4I/JOWyFzglJPM+AUFdxGo0NDGJEMyCx7Xsi7vnXgnisxxuKFm/ChpDou51Mn/fZ1O5glaHc+wXXSL/xquvCxZyCLQGUE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759030163; c=relaxed/simple; bh=FRvaL2Wg4EyPFO/fEOEQG29vNIjx5ngsjCzgfCrtsC4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=QUoLiTcFknt+BgYFQjZqgdCkEXv1gLbfPYZysoKA3VcWiqmm8ofVG75R2kME78IqVJqZwha7SE67oZ9zodxUKoJWybJTirWxOf9JOgoNm7SZCI3RNfWX+bJQjcRRZn8wPNiH9bZnMpV3szzDAe3NanFfpOJ5UVa7WU+eUrHmAlg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=aRkXYT0R; arc=none smtp.client-ip=95.215.58.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="aRkXYT0R" Message-ID: <4e49dc3f-55b9-4ce8-9c45-4973307e5501@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1759030157; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Yn9qblu/XQyxqAgeFSH2EEU3bU1VWGtmwwNHu5zJnOs=; b=aRkXYT0RO2AXnL8R2SeadTCtLF8GIu5VukTu0GiZnEqToCgx3ytvAUcHFLQE+3ZGfZk863 khVzUYxieVE9jbN4TdAIzI5pcCA9IZEUw6LfDYfCY2NaIYnQblpvxQuzTAnPUD7i79OPcv FyOwwp12E5Q260yUiPuqW9gL2CT3qlw= Date: Sun, 28 Sep 2025 11:29:09 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: =?UTF-8?B?UmU6IFvlpJbpg6jpgq7ku7ZdIFJlOiBbUEFUQ0hdIGh1bmdfdGFzazog?= =?UTF-8?Q?Panic_after_fixed_number_of_hung_tasks?= To: "Li,Rongqing" Cc: "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "arnd@arndb.de" , "joel.granados@kernel.org" , "feng.tang@linux.alibaba.com" , "pauld@redhat.com" , "kees@kernel.org" , "rostedt@goodmis.org" , "pawan.kumar.gupta@linux.intel.com" , "akpm@linux-foundation.org" , "dave.hansen@linux.intel.com" , "mingo@kernel.org" , "paulmck@kernel.org" , "corbet@lwn.net" , "mhiramat@kernel.org" References: <20250925060605.2659-1-lirongqing@baidu.com> <3ae5cbea-d320-4d28-a894-5e11e048158f@linux.dev> <819fbfed27cf4e57860645f9edc774a3@baidu.com> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <819fbfed27cf4e57860645f9edc774a3@baidu.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 2025/9/28 11:19, Li,Rongqing wrote: > > >> -----Original Message----- >> From: Lance Yang >> Sent: 2025年9月27日 10:39 >> To: Li,Rongqing >> Cc: linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org; arnd@arndb.de; >> joel.granados@kernel.org; feng.tang@linux.alibaba.com; pauld@redhat.com; >> kees@kernel.org; rostedt@goodmis.org; pawan.kumar.gupta@linux.intel.com; >> akpm@linux-foundation.org; dave.hansen@linux.intel.com; mingo@kernel.org; >> paulmck@kernel.org; corbet@lwn.net; mhiramat@kernel.org >> Subject: [外部邮件] Re: [PATCH] hung_task: Panic after fixed number of hung >> tasks >> >> >> >> On 2025/9/25 14:06, lirongqing wrote: >>> From: Li RongQing >>> >>> Currently, when hung_task_panic is enabled, kernel will panic >>> immediately upon detecting the first hung task. However, some hung >>> tasks are transient and the system can recover fully, while others are >>> unrecoverable and trigger consecutive hung task reports, and a panic is >> expected. >>> >>> This commit adds a new sysctl parameter hung_task_count_to_panic to >>> allows specifying the number of consecutive hung tasks that must be >>> detected before triggering a kernel panic. This provides finer control >>> for environments where transient hangs maybe happen but persistent >>> hangs should still be fatal. >>> >>> Signed-off-by: Li RongQing >>> --- >>> Documentation/admin-guide/sysctl/kernel.rst | 6 ++++++ >>> kernel/hung_task.c | 14 +++++++++++++- >>> 2 files changed, 19 insertions(+), 1 deletion(-) >>> >>> diff --git a/Documentation/admin-guide/sysctl/kernel.rst >>> b/Documentation/admin-guide/sysctl/kernel.rst >>> index 8b49eab..4240e7b 100644 >>> --- a/Documentation/admin-guide/sysctl/kernel.rst >>> +++ b/Documentation/admin-guide/sysctl/kernel.rst >>> @@ -405,6 +405,12 @@ This file shows up if >> ``CONFIG_DETECT_HUNG_TASK`` is enabled. >>> 1 Panic immediately. >>> = ================================================= >>> >>> +hung_task_count_to_panic >>> +===================== >>> + >>> +When set to a non-zero value, after the number of consecutive hung >>> +task occur, the kernel will triggers a panic >> >> Hmm... the documentation here seems a bit misleading. >> >> hung_task_panic=1 will always cause an immediate panic, regardless of the >> hung_task_count_to_panic setting, right? >> >> Perhaps something like this would be more accurate? >> >> ``` >> hung_task_count_to_panic >> ======================== >> >> When set to a non-zero value, a kernel panic will be triggered if the number of >> detected hung tasks reaches this value. >> >> Note that setting hung_task_panic=1 will still cause an immediate panic on the >> first hung task, overriding this setting. >> ``` >> >>> >>> hung_task_check_count >>> ===================== >>> diff --git a/kernel/hung_task.c b/kernel/hung_task.c index >>> 8708a12..87a6421 100644 >>> --- a/kernel/hung_task.c >>> +++ b/kernel/hung_task.c >>> @@ -83,6 +83,8 @@ static unsigned int __read_mostly >> sysctl_hung_task_all_cpu_backtrace; >>> static unsigned int __read_mostly sysctl_hung_task_panic = >>> IS_ENABLED(CONFIG_BOOTPARAM_HUNG_TASK_PANIC); >>> >>> +static unsigned int __read_mostly sysctl_hung_task_count_to_panic; >> >> Nit: while static variables are guaranteed to be zero-initialized, it's a good >> practice and clearer for readers to initialize them explicitly. >> >> static unsigned int __read_mostly sysctl_hung_task_count_to_panic = 0; >> >> > > ./scripts/checkpatch.pl reports error when initialise statics to 0, so I will keep it uninitialized > > ERROR: do not initialise statics to 0 > #51: FILE: kernel/hung_task.c:86: > +static unsigned int __read_mostly sysctl_hung_task_count_to_panic = 0; Ah, good spot! Let’s leave it as is ;) Cheers, Lance > > > thanks > > -Li > >> Otherwise, this patch looks good to me! >> Acked-by: Lance Yang >> >>> + >>> static int >>> hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr) >>> { >>> @@ -219,7 +221,9 @@ static void check_hung_task(struct task_struct *t, >>> unsigned long timeout) >>> >>> trace_sched_process_hang(t); >>> >>> - if (sysctl_hung_task_panic) { >>> + if (sysctl_hung_task_panic || >>> + (sysctl_hung_task_count_to_panic && >>> + (sysctl_hung_task_detect_count >= >>> +sysctl_hung_task_count_to_panic))) { >>> console_verbose(); >>> hung_task_show_lock = true; >>> hung_task_call_panic = true; >>> @@ -388,6 +392,14 @@ static const struct ctl_table hung_task_sysctls[] = { >>> .extra2 = SYSCTL_ONE, >>> }, >>> { >>> + .procname = "hung_task_count_to_panic", >>> + .data = &sysctl_hung_task_count_to_panic, >>> + .maxlen = sizeof(int), >>> + .mode = 0644, >>> + .proc_handler = proc_dointvec_minmax, >>> + .extra1 = SYSCTL_ZERO, >>> + }, >>> + { >>> .procname = "hung_task_check_count", >>> .data = &sysctl_hung_task_check_count, >>> .maxlen = sizeof(int), >