Sleeping process not reported as sleeping
Turning my email into an issue
I’m trying to find out how different lisp compilers handle external processes(*). As a part of that, I’ve created a short piece of code that launches an external process, sends it SIGSTOP
, asks its about its well-being, and allows its to go about its business again by sending SIGCONT
.
I would expect that ext:external-process-status
consequently reports
- :running before
SIGSTOP
is sent - then :stopped
- then :running or :resumed again once
SIGCONT
was received - and finally :exited.
Indeed, that is what ps
would do if you ran it on the command line (so I’ve added that to the example for comparison). Here’s the output of my script:
internal status: RUNNING (expected: running)
internal status: RUNNING (expected: stopped)
internal status: RUNNING (expected: running/resumed)
internal status: EXITED (expected: exited)
My expectations aren’t met in (2): Even though according to the ecl manual the status of a process can be :stopped, and the process is clearly stopped, it is not reported as such.
So I’d like to ask: Is this a bug or intentional?
(*) I’ve already sent very similar messages to openmcl-devel and sbcl-devel.
Here’s the updated script that I used (which now sends SIGSTOP
/SIGCONT
repeatedly:
;; CMUCL: make sure to use a version >21b (not yet released as of 2017-94-04)
;; because of https://gitlab.common-lisp.net/cmucl/cmucl/issues/26
;; ECL: make sure to use a version >16.1.3 (not yet released as of 2017-09-04)
;; because of https://gitlab.com/embeddable-common-lisp/ecl/issues/273
#+clozure (use-package :ccl)
#+sbcl (use-package :sb-ext)
#+cmu (use-package :ext)
#+mkcl (use-package :mk-ext)
#+clozure (setf (fdefinition 'process-output) #'external-process-output-stream)
#+ecl (setf (fdefinition 'process-output) #'ext:external-process-output)
(defun my-run-program (&rest rest)
#+ecl (nth-value 2 (apply #'ext:run-program rest))
#+mkcl (nth-value 1 (apply #'mk-ext:run-program rest))
#-(or ecl mkcl) (apply #'run-program rest))
(defconstant +sigstop+
#+clozure (symbol-value (read-from-string "#$SIGSTOP"))
#+cmu unix:sigstop
#+ecl ext:+sigstop+
#+sbcl (progn (require :sb-posix)
(symbol-value (find-symbol (symbol-name :sigstop)
(find-package :sb-posix))))
#-(or clozure cmu ecl sbcl) (or #+darwin 17 #-darwin 19)) ; FIXME
(defconstant +sigtstp+
#+clozure (symbol-value (read-from-string "#$SIGTSTP"))
#+cmu unix:sigtstp
#+ecl ext:+sigtstp+
#+sbcl (progn (require :sb-posix)
(symbol-value (find-symbol (symbol-name :sigtstp)
(find-package :sb-posix))))
#-(or clozure cmu ecl sbcl) (or #+darwin 18 #-darwin 20)) ; FIXME
(defconstant +sigcont+
#+clozure (symbol-value (read-from-string "#$SIGCONT"))
#+cmu unix:sigcont
#+ecl ext:+sigcont+
#+sbcl (progn (require :sb-posix)
(symbol-value (find-symbol (symbol-name :sigcont)
(find-package :sb-posix))))
#-(or clozure cmu ecl sbcl) (or #+darwin 19 #-darwin 18)) ; FIXME
(defun internal-status (process)
#+clozure (external-process-status process)
#+(or sbcl cmu) (process-status process)
#+ecl (ext:external-process-status process)
#+mkcl (mk-ext:process-status process))
(defun external-kill (pid signal)
(my-run-program "/usr/bin/env" (list "kill"
(format nil "-~a" signal)
(format nil "~a" pid))))
(defun get-pid (process)
#+clozure (ccl::external-process-pid process)
#+ecl (ext:external-process-pid process)
#+(or sbcl cmu) (process-pid process)
#+mkcl (mkcl:process-id process))
(let* ((p (my-run-program "/bin/sleep" '("5") :wait nil))
(pid (get-pid p)))
(format t "internal status: ~a (expected: running)~%" (internal-status p))
(external-kill pid +sigstop+)
(sleep 1)
(format t "internal status: ~a (expected: stopped)~%" (internal-status p))
(external-kill pid +sigcont+)
(sleep 1)
(format t "internal status: ~a (expected: running/resumed)~%" (internal-status p))
(external-kill pid +sigstop+)
(sleep 1)
(format t "internal status: ~a (expected: stopped)~%" (internal-status p))
(external-kill pid +sigcont+)
(sleep 1)
(format t "internal status: ~a (expected: running/resumed)~%" (internal-status p))
(sleep 5)
(format t "internal status: ~a (expected: exited)~%" (internal-status p)))
Update:
The fact that sleeping processes are not reported at all appears to be down to the fact that the line
waitpid(ecl_to_fix(pid), &code_int, Null(wait)? WNOHANG : 0)
from ecl_waitpid defined at src/c/unixsys.d:242 does not contain WUNTRACED
. The fix is not as easy as adding WUNTRACED
, however. Such a change turns running/running/running/exited into running/stopped/stopped/stopped which is an improvement but still not correct.