From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-174.mta0.migadu.com (out-174.mta0.migadu.com [91.218.175.174]) (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 3A7F133A9D8 for ; Wed, 17 Dec 2025 07:31:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.174 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765956703; cv=none; b=Pw2CLgMvZCLhcx3OpaMmsJaW0Svn6XvaB7OQ1tpbMoHItDkNvCir7kh+akmtYmDzdqViwu4w2vibVMr8bcEre0g8zvZ7RTN2fSOQU0FDTkd0YMUqteJSyLN5yY6nu9ycrlVoBaGU3lEOgLaPEevXh0oVkkamK//j2nKaCoOzeO0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765956703; c=relaxed/simple; bh=mEIOZ5zfm7C5AaE1sxPdLkV9PRHjB+V2NZaj7HfyWn4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=RuKyKZDIpOHXxNlarSaHlZeT1RKxO7zF1c2zJqwGPiXS+gLVNZ0L++p092DDilnbFlIMkHQu7Eo9WXeyLkdUvoeGZ1kXLwb+/1eU1c6auNp1dpJiVP4Uso7v2uOKNVYq0JmvPg/fMcAwEUy8wQkgbUPlkgcsalpl9vpk2leCIH0= 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=mhv7Nf0Z; arc=none smtp.client-ip=91.218.175.174 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="mhv7Nf0Z" Message-ID: <79e00527-0ada-4c43-915e-1f8f6589d051@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1765956694; 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=Nb9D9zKInDEO70dJXd+roFzb62VSIN4XBjIQIJ6Y+A8=; b=mhv7Nf0ZSJLFQHE4/GOB/9By0u8r8lQvseqaDFhqanrCxnPlaUAvZ/jajEgI6aXT3DmRL4 f6Y9njbalv+qZF473Gqgf4Ut52k0N2Kl6D2eGKpJ3rINzB2FHmJuF9rRujuM44Np93PM0L 8PXI9wiOi25pL4eS5iTiU0LnpwGS3n8= Date: Wed, 17 Dec 2025 15:31:25 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v3 2/2] hung_task: Enable runtime reset of hung_task_detect_count Content-Language: en-US To: Aaron Tomlin Cc: sean@ashe.io, linux-kernel@vger.kernel.org, pmladek@suse.com, mhiramat@kernel.org, akpm@linux-foundation.org, gregkh@linuxfoundation.org References: <20251216030036.1822217-1-atomlin@atomlin.com> <20251216030036.1822217-3-atomlin@atomlin.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Lance Yang In-Reply-To: <20251216030036.1822217-3-atomlin@atomlin.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2025/12/16 11:00, Aaron Tomlin wrote: > Introduce support for writing to /proc/sys/kernel/hung_task_detect_count. > > Writing any value to this file atomically resets the counter of detected > hung tasks to zero. This grants system administrators the ability to clear > the cumulative diagnostic history after resolving an incident, simplifying > monitoring without requiring a system restart. Thanks! > > Signed-off-by: Aaron Tomlin > --- > Documentation/admin-guide/sysctl/kernel.rst | 2 +- > kernel/hung_task.c | 29 +++++++++++++++++++-- > 2 files changed, 28 insertions(+), 3 deletions(-) > > diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst > index 239da22c4e28..43c17b919969 100644 > --- a/Documentation/admin-guide/sysctl/kernel.rst > +++ b/Documentation/admin-guide/sysctl/kernel.rst > @@ -418,7 +418,7 @@ hung_task_detect_count > ====================== > > Indicates the total number of tasks that have been detected as hung since > -the system boot. > +the system boot. The counter can be reset to zero when written to. > > This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled. > > diff --git a/kernel/hung_task.c b/kernel/hung_task.c > index 5902573200c0..01ce46a107b0 100644 > --- a/kernel/hung_task.c > +++ b/kernel/hung_task.c > @@ -375,6 +375,31 @@ static long hung_timeout_jiffies(unsigned long last_checked, > } > > #ifdef CONFIG_SYSCTL > + > +/** > + * proc_dohung_task_detect_count - proc handler for hung_task_detect_count > + * @table: Pointer to the struct ctl_table definition for this proc entry > + * @write: Flag indicating the operation > + * @buffer: User space buffer for data transfer > + * @lenp: Pointer to the length of the data being transferred > + * @ppos: Pointer to the current file offset > + * > + * This handler is used for reading the current hung task detection count > + * and for resetting it to zero when a write operation is performed. > + * Returns 0 on success or a negative error code on failure. > + */ > +static int proc_dohung_task_detect_count(const struct ctl_table *table, int write, > + void *buffer, size_t *lenp, loff_t *ppos) > +{ > + if (!write) > + return proc_doulongvec_minmax(table, write, buffer, lenp, ppos); > + > + WRITE_ONCE(sysctl_hung_task_detect_count, 0); The reset uses WRITE_ONCE() but the increment in check_hung_task() is plain ++, it's just a stat cunter so fine though ;) Tested-by: Lance Yang Reviewed-by: Lance Yang Cheers, Lance > + *ppos += *lenp; > + > + return 0; > +} > + > /* > * Process updating of timeout sysctl > */ > @@ -457,8 +482,8 @@ static const struct ctl_table hung_task_sysctls[] = { > .procname = "hung_task_detect_count", > .data = &sysctl_hung_task_detect_count, > .maxlen = sizeof(unsigned long), > - .mode = 0444, > - .proc_handler = proc_doulongvec_minmax, > + .mode = 0644, > + .proc_handler = proc_dohung_task_detect_count, > }, > { > .procname = "hung_task_sys_info",