From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-173.mta0.migadu.com (out-173.mta0.migadu.com [91.218.175.173]) (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 1DFAD1E89C for ; Thu, 11 Dec 2025 05:14:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765430088; cv=none; b=Q9602AoImgwUy6JtwW+PrNeI7mVeYzdLtRyum7v8cZyz3ANvv4iBQFotbB203Rhh6qStA9OBwM4znxhlGHPQfs2dDnQRdKz03Pp4bEFJjGDQoExsLBrLUW8nEiawDP2JhE8N7DO+DEqqEOapxHFcp9iuFbJtZO/Vh+gu4PbDwrA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765430088; c=relaxed/simple; bh=9dWvr4eEsdOMrnp0Z9/Xl8JldHE/v75VHc76X6yaWtc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Iv97I0DQvWMld3boSVPOMoEC06DB1GZB24M0o+qEwsZ8yNkCSEhBM57PeRHd/R+ifTuRDBtuqU76pqGuhGm4pDxl1uZ/KmfyjnNL1qX65vFa0oMLVIzaz+ltLoEW7C5av3/I/aizNOxP10o2NVasv+Mt4RHEJ9HfCDM5AB2cORo= 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=FUpP06jZ; arc=none smtp.client-ip=91.218.175.173 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="FUpP06jZ" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1765430084; 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=x4qH3DCbgPLYjee+ES1OkuvIgtPeZwIcv1xbCWPRpKc=; b=FUpP06jZZKCo1RpVyzQeUwEvu3uLVK11lAI7gVf5LM4jiQgdCNd2WxtHYj7hxF8nWvSs2L MmjxnRQ3awjF3dH04+7ndhHzBn6tcHpWjRT+XbWUYmPa1gbShS4jpeS9zSpOtzydJ7O9aW 5tLUjTeYf2MRbG+cICj4LToG6x684j4= Date: Thu, 11 Dec 2025 13:14:38 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v2 2/2] hung_task: Enable runtime reset of hung_task_detect_count To: Aaron Tomlin Cc: sean@ashe.io, linux-kernel@vger.kernel.org, pmladek@suse.com, gregkh@linuxfoundation.org, mhiramat@kernel.org, akpm@linux-foundation.org References: <20251211033004.1628875-1-atomlin@atomlin.com> <20251211033004.1628875-3-atomlin@atomlin.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: <20251211033004.1628875-3-atomlin@atomlin.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 2025/12/11 11:30, 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. > > Signed-off-by: Aaron Tomlin > --- > Documentation/admin-guide/sysctl/kernel.rst | 2 +- > kernel/hung_task.c | 30 +++++++++++++++++++-- > 2 files changed, 29 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 6f3fb26378b5..979b7e2fcc19 100644 > --- a/kernel/hung_task.c > +++ b/kernel/hung_task.c > @@ -377,6 +377,32 @@ static long hung_timeout_jiffies(unsigned long last_checked, > } > > #ifdef CONFIG_SYSCTL > + > +/** > + * proc_dohung_task_detect_count - proc handler for hung_task_detect_count > + * > + * Handles read access for the hung task counter. For write access, it > + * accepts any successfully parsed value and atomically resets the counter > + * to zero. Returns the byte count written 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) > +{ > + int ret; > + > + if (!write) > + return proc_doulongvec_minmax(table, write, buffer, lenp, ppos); > + > + ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); Since the intent is "any write resets to zero", we could skip parsing the input entirely (untested): WRITE_ONCE(sysctl_hung_task_detect_count, 0); *ppos += *lenp; return 0; See vmstat_refresh() for a similar pattern :) > + if (ret) > + return ret; > + > + WRITE_ONCE(sysctl_hung_task_detect_count, 0); > + > + return ret; > +} Cheers, Lance > + > /* > * Process updating of timeout sysctl > */ > @@ -459,8 +485,8 @@ 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",