CreateEvent multiple listeners - multithreading

Question

I'm trying to receive an event in multiple instances of my application.
For that purpose I've created a small demo program. First my TWorkerThread:
unit WorkerThreadU;
interface
uses
WinAPI.Windows, System.Classes;
type
TOnUpdate = reference to procedure(const Value: Integer);
TWorkerThread = class(TThread)
private
FUpdate: THandle;
FValue: Integer;
FResult: Integer;
FUpdateReady: TOnUpdate;
protected
procedure Execute; override;
public
constructor Create;
destructor Destroy; override;
procedure Update;
property Value: Integer read FValue write FValue;
property OnUpdate: TOnUpdate read FUpdateReady write FUpdateReady;
end;
implementation
{ TWorkerThread }
constructor TWorkerThread.Create;
begin
inherited Create(False);
FUpdate := CreateEvent(nil, False, False, '{B2DCFF9B-ABF7-49BA-8B7C-4F63EF20D99E}');
end;
destructor TWorkerThread.Destroy;
begin
CloseHandle(FUpdate);
inherited;
end;
procedure TWorkerThread.Execute;
begin
while not Terminated do
begin
if WaitForSingleObject(FUpdate, 1000) <> WAIT_OBJECT_0 then
continue;
FResult := FValue * 2;
if not Assigned(FUpdateReady) then
continue;
TThread.Queue(nil,
procedure
begin
FUpdateReady(FResult);
end);
end;
end;
procedure TWorkerThread.Update;
begin
SetEvent(FUpdate);
end;
end.
My form:
...and the source for it:
procedure TfrmEvents.FormCreate(Sender: TObject);
begin
Caption := BoolToStr(Boolean(IsDebuggerPresent), True);
FWorkerThread := TWorkerThread.Create;
FWorkerThread.OnUpdate := procedure(const Value: Integer)
begin
Log(Format('2 * %d = %d', [inpValue.Value, Value]))
end;
end;
procedure TfrmEvents.btnCalcClick(Sender: TObject);
begin
try
FWorkerThread.Value := inpValue.Value;
Log('Calculating ...');
FWorkerThread.Update;
finally
end;
end;
procedure TfrmEvents.Log(const msg: string);
begin
lbLog.ItemIndex := lbLog.Items.Add(FormatDateTime('hh:nn:ss', Now) + ' ' + msg);
end;
My problem is that only one of the instances receives the event.
The program can also be found here.

Answer 1

This probably happens because CreateEvent uses the same name for all thread instances. That way all threads use the same event. As the event is created with automatic reset, the first thread getting the event will reset it and the others aren't noticed anymore.
From the docs:
If this parameter is FALSE, the function creates an auto-reset event
object, and system automatically resets the event state to nonsignaled
after a single waiting thread has been released.