The command `ps -ef ` and `top -c` mark kernel thread by '['
and ']', but sometimes the result is not correct.
The task->flags in /proc/$pid/stat is good, but we need remember
the value of PF_KTHREAD is 0x00200000 and convert dec to hex.
If we have no binary program and shell script which read
/proc/$pid/stat, we can know it directly by
`cat /proc/$pid/status`.

Signed-off-by: Chunguang Wu <fullspring2018@gmail.com>
---
 fs/proc/array.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 9b0315d34c58..fde6a0b92728 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -434,6 +434,13 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
 
 	task_state(m, ns, pid, task);
 
+	seq_puts(m, "Kthread:\t");
+	if (task->flags & PF_KTHREAD) {
+		seq_puts(m, "1\n");
+	} else {
+		seq_puts(m, "0\n");
+	}
+
 	if (mm) {
 		task_mem(m, mm);
 		task_core_dumping(m, task);
-- 
2.39.1

Hi--

On 4/14/23 02:27, Chunguang Wu wrote:
> The command `ps -ef ` and `top -c` mark kernel thread by '['
> and ']', but sometimes the result is not correct.
> The task->flags in /proc/$pid/stat is good, but we need remember
> the value of PF_KTHREAD is 0x00200000 and convert dec to hex.
> If we have no binary program and shell script which read
> /proc/$pid/stat, we can know it directly by
> `cat /proc/$pid/status`.
> 

Please update Documentation/filesystems/proc.rst:

(1) the example:
For example, to get the status information of a process, all you have to do is
read the file /proc/PID/status::

and (2): table 1-2

Thanks.

> Signed-off-by: Chunguang Wu <fullspring2018@gmail.com>
> ---
>  fs/proc/array.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/fs/proc/array.c b/fs/proc/array.c
> index 9b0315d34c58..fde6a0b92728 100644
> --- a/fs/proc/array.c
> +++ b/fs/proc/array.c
> @@ -434,6 +434,13 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
>  
>  	task_state(m, ns, pid, task);
>  
> +	seq_puts(m, "Kthread:\t");
> +	if (task->flags & PF_KTHREAD) {
> +		seq_puts(m, "1\n");
> +	} else {
> +		seq_puts(m, "0\n");
> +	}
> +
>  	if (mm) {
>  		task_mem(m, mm);
>  		task_core_dumping(m, task);

-- 
~Randy