fs/proc: add Kthread flag to /proc/$pid/status

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`.

Link: https://lkml.kernel.org/r/20230416052404.2920-1-fullspring2018@gmail.com
Signed-off-by: Chunguang Wu <fullspring2018@gmail.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 9d5fd9424e8bbdc7dfa6567908282612d4d26ec0..8a563684586c509ce76bc04549950c4a3059cbe8 100644 (file)
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -179,6 +179,7 @@ read the file /proc/PID/status::
   Gid:    100     100     100     100
   FDSize: 256
   Groups: 100 14 16
+  Kthread:    0
   VmPeak:     5004 kB
   VmSize:     5004 kB
   VmLck:         0 kB
@@ -256,6 +257,7 @@ It's slow but very precise.
  NSpid                       descendant namespace process ID hierarchy
  NSpgid                      descendant namespace process group ID hierarchy
  NSsid                       descendant namespace session ID hierarchy
+ Kthread                     kernel thread flag, 1 is yes, 0 is no
  VmPeak                      peak virtual memory size
  VmSize                      total program size
  VmLck                       locked memory size

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 9b0315d34c58fb3d1780901cd420d02d1d53f269..425824ad85e12d3c6d0439f0b4a0c10b5f546354 100644 (file)
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -219,6 +219,8 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
                seq_put_decimal_ull(m, "\t", task_session_nr_ns(p, pid->numbers[g].ns));
 #endif
        seq_putc(m, '\n');
+
+       seq_printf(m, "Kthread:\t%c\n", p->flags & PF_KTHREAD ? '1' : '0');
 }
 
 void render_sigset_t(struct seq_file *m, const char *header,