linux-kernel - Re: [PATCH 2/3] hung_task: Add hung_task_sys_info sysctl to dump sys info on task-hung

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Message-ID: <aRRupyzGaP5Z35qE@U-2FWC9VHC-2323.local>
Date: Wed, 12 Nov 2025 19:25:27 +0800
From: Feng Tang <feng.tang@...ux.alibaba.com>
To: Petr Mladek <pmladek@...e.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Lance Yang <ioworker0@...il.com>, paulmck@...nel.org,
	Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] hung_task: Add hung_task_sys_info sysctl to dump sys
 info on task-hung

On Mon, Nov 10, 2025 at 06:55:57PM +0100, Petr Mladek wrote:
> On Thu 2025-11-06 10:30:31, Feng Tang wrote:
[...]
> @@ -315,8 +295,10 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
>  {
>  	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;
> +	unsigned long si_mask;
>  
>  	/*
>  	 * If the system crashed already then all bets are off,
> @@ -325,6 +307,14 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
>  	if (test_taint(TAINT_DIE) || did_panic)
>  		return;
>  
> +	si_mask = hung_task_si_mask;
> +	if (sysctl_hung_task_warnings || hung_task_call_panic) {
> +		si_mask |= SYS_INFO_LOCKS;
> +
> +		if (sysctl_hung_task_all_cpu_backtrace)
> +			si_mask |= SYS_INFO_ALL_BT;
> +	}

This probably needs to be moved to after the loop check of
check_hung_task(). 

> +
>  	rcu_read_lock();
>  	for_each_process_thread(g, t) {
>  
> @@ -336,16 +326,20 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
>  			last_break = jiffies;
>  		}
>  
> -		check_hung_task(t, timeout, prev_detect_count);
> +		check_hung_task(t, timeout);
>  	}
>   unlock:
>  	rcu_read_unlock();
>  
> -	if (unlikely(cur_si_mask)) {
> -		sys_info(cur_si_mask);
> -		cur_si_mask = 0;
> +	total_hung_task = sysctl_hung_task_detect_count - prev_detect_count;
> +	if (sysctl_hung_task_panic && total_hung_task >= sysctl_hung_task_panic) {
> +		console_verbose();
> +		hung_task_call_panic = true;
>  	}
>  
> +	if (unlikely(si_mask))
> +		sys_info(si_mask);
> +
>  	if (hung_task_call_panic)
>  		panic("hung_task: blocked tasks");
>  }
[...]

Thanks,
Feng