[fpc-pascal] Various Darwin problems

[Paul Davidson]

Modified program by creating threads resumed (not suspended),
then using new loop to start each one.

Though new loop completes, and threads are created (31 inclucing 
process),
they refuse to be terminated.  It seems that RESUME, at least from 
another thread, if faulty.

As well, CPU utilization is still near 100%

program TestResume;

{$mode objfpc}{$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;
   Suspend;
   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(TRUE);
   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( 'Waking threads' );
   fpGetTimeOfDay( @ti1, @tiz );
   for i:=1 to MAX do
     a[i].Resume;
   fpGetTimeOfDay( @ti2, @tiz );
   Writeln('Threads woke 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.

On Oct 11, 2005, at 9:07, Marco van de Voort wrote:

>>>> 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.
>

P Davidson