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: <aRSdOfA3bgvCzdfH@pathway.suse.cz>
Date: Wed, 12 Nov 2025 15:44:09 +0100
From: Petr Mladek <pmladek@...e.com>
To: Feng Tang <feng.tang@...ux.alibaba.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 Wed 2025-11-12 19:25:27, Feng Tang wrote:
> 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(). 

I did it on purpose because "sysctl_hung_task_warnings" might get
decremented down to "0" in the loop below. But IMHO, we need to print
the information if it was non-zero at the beginning.

It might be worth to add a comment why it has to be done
before the cycle.

> > +
> >  	rcu_read_lock();
> >  	for_each_process_thread(g, t) {
> >  

Best Regards,
Petr