[fpc-pascal] Various Darwin problems

[Marco van de Voort]

> > > doesn't accept
> > > sleeps smaller than 10ms.
> >
> > That is not true. This program takes half a second on my machine:
> 
> This only happens because you are getting a very big time period on
> your test. Sleep, nanosleep and all other timing procedures are simply
> *not* reliable when you want a microsecond or 1milisecond precision.

This is a general problem for preemptive OSes. I had problems with Darwin
beyond that, iow magnitudes more than expected. 

In the demo below for high values (100ms) in the thread.execute sleep, threadshutdown
is swift (few hunderd ms). For short ones, it isn't (few sec).

P. Davidson came with the problem, Almindor with the test, and I could
duplicate the problem, but not explain it. Maybe the larger pauze avoids
shutting all 30 threads at once, and is _that_ (30 threads shutting down
at once) the problem.

program project1;

{$mode objfpc}{$H+}

uses
  cThreads, BaseUnix, Unix, Classes;
  
const
  MAX = 30;
  
type
  TThr = class(TThread)
   protected
    procedure Execute; override;
  end;

var
	ti1 : timeval;
	ti2 : timeval;
	tiz : timezone;

procedure TThr.Execute;
var
  T1, T2: Ttimespec;
begin
  T1.tv_sec:=0;
  T1.tv_nsec:=1000;
  while not Terminated do
    FpNanoSleep(@T1, @T2);
end;

var
  a: array[1..MAX] of TThr;
  i: Integer;
  T1, T2: Ttimespec;
begin
  T1.tv_sec:=10;
  T1.tv_nsec:=0;
  // Set up time
  fpGetTimeOfDay( @ti1, @tiz );
  for i:=1 to MAX do
    a[i]:=TThr.Create(False);
  fpGetTimeOfDay( @ti2, @tiz );
  Writeln('Threads created in ', 
           ( ( ( extended( ti2.tv_sec )   * 1000000 + ti2.tv_usec ) - 
		   ( extended( ti1.tv_sec ) * 1000000 + ti1.tv_usec ) ) / 1000 ):7:3, 'mS' );
  writeln( 'Waiting 10 seconds' );
  FpNanoSleep(@T1, @T2);
  Write('Freeing threads... ');
  fpGetTimeOfDay( @ti1, @tiz );
  for i:=1 to MAX do begin
    a[i].Terminate;
    a[i].WaitFor;
    a[i].Free;
  end;
  fpGetTimeOfDay( @ti2, @tiz );
  Writeln('Threads destroyed in ', 
           ( ( ( extended( ti2.tv_sec )   * 1000000 + ti2.tv_usec ) - 
		   ( extended( ti1.tv_sec ) * 1000000 + ti1.tv_usec ) ) / 1000 ):10:3, 'mS' );
  Writeln('Done');
end.