TTimer.OnTimer会导致工作线程与主线程同步吗？

Question

I have to work with legacy code. This code has a TTimer created in a main thread. In OnTimer event the timer is checking periodically a state of some data in the worker thread.

pseudocode:

procedure MainForm.OnTimer(Sender: TObject);
begin
  if WorkerThread.Data.State = full then
  begin
    WorkerThread.Free; //This freezes GUI.    
  end else
   //Do something else.
end;

The problem is that I want to do some background operation when the WorkerThread is terminating. To avoid synchronization I've overriden DoTerminate method. However in this particular case, this is not helping and my GUI becomes frozen until the DoTerminate finishes.

Can I somehow avoid the freeze?

Thanks.

Answer 1

There's not enough code here to say anything with any certainty. However, calling Free on a thread results in a call to Terminate followed by a WaitFor . It's quite plausible that the wait is not returning which would be consistent with the frozen UI.

Answer 2

This is truly backwards. In any decent threading scheme, your thread will be notifying your gui-thread about a condition like .Data.State = full. You gui-thread or main-thread will then take appropriate action. One thing i am certain about is that WorkerThread.Free must be wrong. Trying to free a thread that's apparently blocked for whatever reason, is guaranteed to fail. Thread.Terminate will also fail if the thread is blocked, so no help there either.

Having a Timer monitor the status of a thread is never right. I never use the words always and never, but... I'll repeat: Having a Timer monitor the status of a thread is never right. Never ever. Don't even think about it.

• turin