[Openmcl-devel] Sleeping processes never go back to being marked as running

[Gary Byers]

On 08/03/2016 11:35 AM, Elias Pipping wrote:
> Dear list,
>
> 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 ccl:external-process-status consequently reports
>
> (1) :running before SIGSTOP is sent
> (2) then :stopped
> (3) then :running again once SIGCONT was received
> (4) 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:
>
> external status: [S] (expected: [S])
> internal status: RUNNING (expected: running)
> external status: [T] (expected: [T])
> internal status: STOPPED (expected: stopped)
> external status: [S] (expected: [S])
> internal status: STOPPED (expected: running)
> external status: [] (expected: [] or [Z])
> internal status: EXITED (expected: exited)
>
> My expectations aren’t met in (3): The SIGCONT prompts the process to continue its work but ccl continues to report its status as :stopped, which I find rather confusing.
>
> So I’d like to ask: Is this a bug or intentional?

I think that it's a bug, and opened a trac ticket for it:
http://trac.clozure.com/ccl/ticket/1375

>
>
> Elias Pipping
>
> (*) I’m sending a very similar message to sbcl-devel.
>
> PS: Here’s the script that I used:
>
> #+clozure (use-package :ccl)
> #+sbcl (use-package :sb-ext)
>
> ;; FIXME: this is not portable! Works on linux for now.
> ;; sbcl has constants but does clozure cl?
> (defconstant +sigstop+ 19)
> (defconstant +sigcont+ 18)
>
> (defun internal-status (process)
>    #+clozure (ccl:external-process-status process)
>    #+sbcl (sb-ext:process-status process))
>
> (defun external-kill (pid signal)
>    (run-program "/usr/bin/env" (list "kill"
>                                      (format nil "-~a" signal)
>                                      (format nil "~a" pid))))
>
> (defun external-status (pid)
>    (let ((stream (make-string-output-stream)))
>      (let ((arg-list (list "ps" "-h" "-p" (format nil "~a" pid) "-o" "state")))
>        (run-program "/usr/bin/env" arg-list :output stream))
>      (string-right-trim '(#\Newline) (get-output-stream-string stream))))
>
> (defun get-pid (process)
>    #+clozure (ccl::external-process-pid process)
>    #+sbcl (sb-ext:process-pid process))
>
> (let* ((p (run-program "/usr/bin/env" '("sleep" "3") :wait nil))
>         (pid (get-pid p)))
>    (format t "external status: [~a] (expected: [S])~%" (external-status pid))
>    (format t "internal status: ~a (expected: running)~%" (internal-status p))
>    
>    (external-kill pid +sigstop+)
>    (sleep 1)
>    (format t "external status: [~a] (expected: [T])~%" (external-status pid))
>    (format t "internal status: ~a (expected: stopped)~%" (internal-status p))
>
>    (external-kill pid +sigcont+)
>    (sleep 1)
>    (format t "external status: [~a] (expected: [S])~%" (external-status pid))
>    (format t "internal status: ~a (expected: running)~%" (internal-status p))
>
>    (sleep 3)
>    (format t "external status: [~a] (expected: [] or [Z])~%" (external-status pid))
>    (format t "internal status: ~a (expected: exited)~%" (internal-status p)))
>
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