Is there any implementation for Mutex in FPC?
I have a piece of code in a procedure that I want to be accessible from one of many available threads, at a time.

While searching I found a post that announced Mutex is not implemented in FPC and suggest to use RTLCiticalSection
(http://lists.freepascal.org/lists/fpc-pascal/2006-July/011295.html). Is there any article about it?

Yours,
Amir

There's no "visible" mutex interface in fpc right now. ATM all non-windows platforms have semaphores in the ThreadManager but the windows ones afaik don't.

I think you can simply use CriticalSection instead of mutex to achieve what you need.

Ales

Let me explain the problem with more details,

consider the following code:

while true do
begin
  ReadLn (S);
/// Lock Mutex
  AThread:= TMyThread.Create (True);//Suspended
  AThread.Prepare (S);
  AThread.Resume;
///UnLock Mutex
end;
...

To understand the EnterCriticalsection, I write the following code, I was expect to see a single "Here" while a lot of here is printed. Was I incorrect in anywhere?

  InitCriticalSection (cs);
  while true do
  begin
    EnterCriticalsection (cs);
    WriteLn ('Here!');
  end;
    LeaveCriticalsection (cs);

I referred to a document about EnterCriticalsection, It said that It prevent two different thread to access a critical section, but here

Criticalsections are like recursive mutexes

Peter

Each Enter.. must be matched by a Leave..., and you don't need the loop. The standard way of doing this is:

EnterCriticalsection (cs);
try
   WriteLn ('Here!');
finally
   LeaveCriticalsection (cs);
end;

I'm sure that this is clear for Amir. But in his example he (and me too) expects that the loop should stop at the second time it calls EnterCriticalsection() because the old critical section wasn't left.

But this is not an example to show how a critical section stops another one.

Regards

Michael

Thanks Michael, you are right!
I want to know how should I use Criticalsections to make my program to print only one "here".

loop. The standard way of doing this is:

I'm sure that this is clear for Amir. But in his example he (and me too)

expects that the loop should stop at the second time it calls EnterCriticalsection() because the old critical section wasn't left.

Amir Avani wrote

Thanks Michael, you are right! I want to know how should I use Criticalsections to make my program to print only one "here".

By not using them at all?

count := 0;
while true do
begin
    if count = 0
       WriteLn ('Here!');
    count := 1;
end {while};

Critical sections don't make sense in a non-threading context.

Vinzent.

What you suggested is a kind of busy waiting. But I want a suspension. In a message , i described my main problem which was a while like this.

while true do
begin
 ReadLn (S);
/// Lock Mutex
 AThread:= TMyThread.Create (True);//Suspended
 AThread.Prepare (S);
 AThread.Resume;
///UnLock Mutex
end;

And I told to check if Criticalsession could work in my situation i write that sample code.

Any idea for my problem?