+ hung_task-enable-runtime-reset-of-hung_task_detect_count.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: hung_task: enable runtime reset of hung_task_detect_count
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     hung_task-enable-runtime-reset-of-hung_task_detect_count.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/hung_task-enable-runtime-reset-of-hung_task_detect_count.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Aaron Tomlin <atomlin@atomlin.com>
Subject: hung_task: enable runtime reset of hung_task_detect_count
Date: Mon, 15 Dec 2025 22:00:36 -0500

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.

Link: https://lkml.kernel.org/r/20251216030036.1822217-3-atomlin@atomlin.com
Signed-off-by: Aaron Tomlin <atomlin@atomlin.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Documentation/admin-guide/sysctl/kernel.rst |    2 -
 kernel/hung_task.c                          |   29 ++++++++++++++++--
 2 files changed, 28 insertions(+), 3 deletions(-)

--- a/Documentation/admin-guide/sysctl/kernel.rst~hung_task-enable-runtime-reset-of-hung_task_detect_count
+++ a/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.
 
--- a/kernel/hung_task.c~hung_task-enable-runtime-reset-of-hung_task_detect_count
+++ a/kernel/hung_task.c
@@ -375,6 +375,31 @@ static long hung_timeout_jiffies(unsigne
 }
 
 #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);
+	*ppos += *lenp;
+
+	return 0;
+}
+
 /*
  * Process updating of timeout sysctl
  */
@@ -457,8 +482,8 @@ static const struct ctl_table hung_task_
 		.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",
_

Patches currently in -mm which might be from atomlin@atomlin.com are

hung_task-introduce-helper-for-hung-task-warning.patch
hung_task-enable-runtime-reset-of-hung_task_detect_count.patch