Re: [PATCH] fs/proc: add Kthread flag to /proc/$pid/status

[Alexey Dobriyan <adobriyan@gmail.com>]

On Wed, Apr 12, 2023 at 02:12:16PM -0700, Andrew Morton wrote:
> On Wed, 12 Apr 2023 22:34:02 +0800 Chunguang Wu <aman2008@qq.com> wrote:
> 
> > user can know that a process is kernel thread or not.
> > 
> > ...
> >
> > --- a/fs/proc/array.c
> > +++ b/fs/proc/array.c
> > @@ -434,6 +434,12 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
> >  
> >  	task_state(m, ns, pid, task);
> >  
> > +	if ((mm == NULL) || (task->flags & PF_KTHREAD)) {
> > +		seq_puts(m, "Kthread:\tYes\n");
> > +	} else {
> > +		seq_puts(m, "Kthread:\tNo\n");
> > +	}

"mm" check is redundant. PF_KTHREAD should be enough.
If you're doing this, just print 0/1. 

> >  	if (mm) {
> >  		task_mem(m, mm);
> >  		task_core_dumping(m, task);
> 
> Well..   Why is this information useful?

I want to add: for a shell script.
Real programs can read /proc/*/stat .

> What is the use case?
> 
> There are many ways of working this out from the existing output - why
> is this change required?