[M3devel] variations of waitpid..?

[Jay]

variations of waitpid..

 Hey, we already have, that I put in on my initiative, months ago: 

  C:\dev2\cm3.2\m3-libs\m3core\src\thread\POSIX\ThreadPosix.m3  
 
PROCEDURE WaitProcess (pid: int): int =
(* ThreadPThread.m3 and ThreadPosix.m3 are the same here except ThreadPosix.m3 calls Pause(). *)
  VAR
    result: int;
    statusM3: Uwaitpid.waitpid_status_t;
  CONST Delay = 0.1D0;
  BEGIN
    LOOP
      result := Uwaitpid.waitpid(pid, statusM3, Uwaitpid.WNOHANG);
      IF result # 0 THEN EXIT END;
      Pause(Delay);
    END;
     0 *>
    RETURN statusM3.w_Loophole;
  END WaitProcess;

pthreads and cygwin:

C:\dev2\cm3.2\m3-libs\m3core\src\thread\WIN32\WaitProcessCygwin.m3
and
C:\dev2\cm3.2\m3-libs\m3core\src\thread\PTHREAD\ThreadPThread.m3
 
PROCEDURE WaitProcess (pid: int): int =
  (* ThreadPThread.m3 and ThreadPosix.m3 are very similar. *)
  VAR
    statusM3: Uwaitpid.waitpid_status_t;
  BEGIN
    LOOP
      WITH r = Uwaitpid.waitpid(pid, statusM3) DO
        IF r> 0 THEN
          RETURN statusM3.w_Loophole;
        END;
        < 0*>
      END;
      
    END;
  END WaitProcess;
 
win32:
PROCEDURE WaitProcess (pid: int): int =
  BEGIN
    
    RETURN 0; 
  END WaitProcess;

ThreadPThread and WaitProcessCygwin should share code, but that's not the point.

However, now, to fix sysutils, we need something LIKE:

UNSAFE INTERFACE SystemPosixWaitPid;
FROM Ctypes IMPORT int;
FROM Sysutils_Uwaitpid IMPORT waitpid_status_t;
FROM Utypes IMPORT pid_t;
 
PROCEDURE WaitPid(pid: pid_t; VAR status: waitpid_status_t): int;
 
BEGIN
END SystemPosixWaitPid.

pthreads:
 
UNSAFE MODULE SystemPosixWaitPidEfficient EXPORTS SystemPosixWaitPid;
 
FROM Ctypes IMPORT int;
FROM Sysutils_Uwaitpid IMPORT waitpid_status_t, waitpid;
FROM Utypes IMPORT pid_t;
 
PROCEDURE WaitPid(pid: pid_t; VAR status: waitpid_status_t): int =
  BEGIN
    RETURN waitpid(pid, status, 0);
  END WaitPid;
 
BEGIN
END SystemPosixWaitPidEfficient.

user threads:
 
UNSAFE MODULE SystemPosixWaitPidPause EXPORTS SystemPosixWaitPid;
 
FROM Ctypes IMPORT int;
FROM Sysutils_Uwaitpid IMPORT waitpid_status_t, waitpid;
FROM Utypes IMPORT pid_t;
 
PROCEDURE WaitPid(pid: pid_t; VAR status: waitpid_status_t): int =
  VAR result: int;
  CONST Delay = 0.1D0;
  BEGIN
    LOOP
      result := waitpid(pid, status, Sysutils_Uwaitpid.WNOHANG);
      IF result # 0 THEN
        EXIT
      END;
      Thread.Pause(Delay)
    END;
  END WaitPid;
 
BEGIN
END SystemPosixWaitPidPause.

questions:

Aside: Where do I put "unsafe"?

Relevant: Sysutils has to implement this itself, right?
Due to bootstrapping concerns.

But we should still put /something/ in m3core, right?

So then the big question, what to call it?

Probably, the existing WaitProcess that does more than this WaitPid, should be scaled
back and only do what WaitPid does?

I will likely commit exactly what is shown above.
  The new interface and modules are in sysutils. The interface is private.

The unfinished part is putting something in m3core, that sysutils could use, if
not for boostrapping issuers, that it could use in the future.

I kind of thing something a bit more is needed.
You know, the Win32 implementation that asserts(false) is suspicious.
At the very least, it should be removed.

I suspect I am missing something though, as suggested by Win32 having an assert(false) implementation.
Either that needs to be removed, or somehow the code can be unified, using just the existing m3core/libm3
interfaces?

I also suspect part of the problem is that sysutils implements to a large extent
the same abstractions as m3core and/or libm3, but with variations, causing it to be unable
to build on what is there, but having to reinvent..which suggests the m3core/libm3 abstractions
maybe are not general/featureful enough.
 
(Btw, unstated above, is that sysutils/m3makefile will have the same sort of switch as m3core does, wrt if it builds for user/alaram threads or kernel/pthreads.)
 

??

 - Jay