Re: GNU Shepherd 0.10.3 released

[Ludovic Courtès]

Hi,

Tomas Volf <~@wolfsden.cz> skribis:

> Ah, that code indeed returns #f for the pid in question:
>
>     scheme@(guix-user)> ((@@ (guix build syscalls) kernel?) 688)
>     $1 = #f
>
> The stat file:
>
>     $ cat /proc/688/stat
>     688 (mt76-tx phy0) S 2 0 0 0 -1 2129984 0 0 0 0 0 0 0 0 -2 0 1 0 964 0 0 
> 18446744073709551615 0 0 0 0 0 0 0 2147483647 0 0 0 0 17 5 1 1 0 0 0 0 0 0 0 
> 0 0 0 0
>
> So the start_code is not zero (I would guess it is -1).  I have no idea what
> that means though.

What about this method (from shepherd)?

--8<---------------cut here---------------start------------->8---
(define (linux-process-flags pid)
  "Return the process flags of @var{pid} (or'd @code{PF_} constants), assuming
the Linux /proc file system is mounted; raise a @code{system-error} exception
otherwise."
  (call-with-input-file (string-append "/proc/" (number->string pid)
                                       "/stat")
    (lambda (port)
      (define line
        (get-string-all port))

      ;; Parse like systemd's 'is_kernel_thread' function.
      (let ((offset (string-index line #\))))     ;offset past 'tcomm' field
        (match (and offset
                    (string-tokenize (string-drop line (+ offset 1))))
          ((state ppid pgrp sid tty-nr tty-pgrp flags . _)
           (or (string->number flags) 0))
          (_
           0))))))

;; Per-process flag defined in <linux/sched.h>.
(define PF_KTHREAD #x00200000)                    ;I am a kernel thread

(define (linux-kernel-thread? pid)
  "Return true if @var{pid} is a Linux kernel thread."
  (= PF_KTHREAD (logand (linux-process-flags pid) PF_KTHREAD)))
--8<---------------cut here---------------end--------------->8---

If it works better, we can use that in syscalls.scm as well.

Ludo’.

PS: Having an entry in bug-guix would ensure we don’t lose track of this.