linux-kernel - Re: [PATCH v2 2/4] hung_task: Add hung_task_sys_info sysctl to dump sys info on task-hung

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Message-Id: <20251117095352.8dfb46ec468ba5a69a829031@linux-foundation.org>
Date: Mon, 17 Nov 2025 09:53:52 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Feng Tang <feng.tang@...ux.alibaba.com>
Cc: Lance Yang <lance.yang@...ux.dev>, Petr Mladek <pmladek@...e.com>,
 Steven Rostedt <rostedt@...dmis.org>, Lance Yang <ioworker0@...il.com>,
 linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
 paulmck@...nel.org, lirongqing@...du.com, leonylgao@...cent.com
Subject: Re: [PATCH v2 2/4] hung_task: Add hung_task_sys_info sysctl to dump
 sys info on task-hung

On Sun, 16 Nov 2025 22:13:58 +0800 Feng Tang <feng.tang@...ux.alibaba.com> wrote:

> > >   	if (need_warning || hung_task_call_panic) {
> > >   		si_mask |= SYS_INFO_LOCKS;
> > 
> > Looks good to me now! I assume v3 would be expected, can you
> > post a new version?
> 
> Andrew has taken the patchset to -mm tree. 
> 
> Andrew, which way do you prefer? I send a v3 patch for hung-task or you
> pickup the fixup patch and squash it into the orginal 0002 patch?
> 
> Anyway, I make a squshed version v3 patch below.

I prefer little fixup patches, generally.  So people can see what
changed and don't feel they should re-review everything.

I queued the below, thanks.


From: Feng Tang <feng.tang@...ux.alibaba.com>
Subject: hung_task-add-hung_task_sys_info-sysctl-to-dump-sys-info-on-task-hung-fix
Date: Wed, 5 Nov 2025 19:30:36 +0800

maintain consistecy established behavior, per Lance and Petr

Link: https://lkml.kernel.org/r/aRncJo1mA5Zk77Hr@U-2FWC9VHC-2323.local
Suggested-by: Petr Mladek <pmladek@...e.com>
Signed-off-by: Feng Tang <feng.tang@...ux.alibaba.com>
Cc: Jonathan Corbet <corbet@....net>
Cc: Lance Yang <ioworker0@...il.com>
Cc: "Paul E . McKenney" <paulmck@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 kernel/hung_task.c |   24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

--- a/kernel/hung_task.c~hung_task-add-hung_task_sys_info-sysctl-to-dump-sys-info-on-task-hung-fix
+++ a/kernel/hung_task.c
@@ -223,8 +223,11 @@ static inline void debug_show_blocker(st
 }
 #endif
 
-static void check_hung_task(struct task_struct *t, unsigned long timeout)
+static void check_hung_task(struct task_struct *t, unsigned long timeout,
+		unsigned long prev_detect_count)
 {
+	unsigned long total_hung_task;
+
 	if (!task_is_hung(t, timeout))
 		return;
 
@@ -234,13 +237,19 @@ static void check_hung_task(struct task_
 	 */
 	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 && total_hung_task >= sysctl_hung_task_panic) {
+		console_verbose();
+		hung_task_call_panic = true;
+	}
+
 	/*
 	 * Ok, the task did not get scheduled for more than 2 minutes,
 	 * complain:
 	 */
-	if (sysctl_hung_task_warnings) {
+	if (sysctl_hung_task_warnings || hung_task_call_panic) {
 		if (sysctl_hung_task_warnings > 0)
 			sysctl_hung_task_warnings--;
 		pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n",
@@ -295,7 +304,6 @@ static void check_hung_uninterruptible_t
 {
 	int max_count = sysctl_hung_task_check_count;
 	unsigned long last_break = jiffies;
-	unsigned long total_hung_task;
 	struct task_struct *g, *t;
 	unsigned long prev_detect_count = sysctl_hung_task_detect_count;
 	int need_warning = sysctl_hung_task_warnings;
@@ -320,20 +328,14 @@ static void check_hung_uninterruptible_t
 			last_break = jiffies;
 		}
 
-		check_hung_task(t, timeout);
+		check_hung_task(t, timeout, prev_detect_count);
 	}
  unlock:
 	rcu_read_unlock();
 
-	total_hung_task = sysctl_hung_task_detect_count - prev_detect_count;
-	if (!total_hung_task)
+	if (!(sysctl_hung_task_detect_count - prev_detect_count))
 		return;
 
-	if (sysctl_hung_task_panic && total_hung_task >= sysctl_hung_task_panic) {
-		console_verbose();
-		hung_task_call_panic = true;
-	}
-
 	if (need_warning || hung_task_call_panic) {
 		si_mask |= SYS_INFO_LOCKS;
 
_