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POWith what delphi Code should I replace my calls to deprecated TThread method Suspend?
 

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  1. POWith what delphi Code should I replace my calls to deprecated TThread method Suspend?
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    <p>It has been asked before, but <a href="https://stackoverflow.com/questions/1418333/tthread-resume-is-deprecated-in-delphi-2010-what-should-be-used-in-place">without a full answer</a>. This is to do with the so called famous "‘Fatal threading model!’".</p> <p>I need to replace this call to TThread.Suspend with something safe, that returns when terminated or resumed:</p> <pre><code>procedure TMyThread.Execute; begin while (not Terminated) do begin if PendingOffline then begin PendingOffline := false; // flag off. ReleaseResources; Self.Suspend; // suspend thread. { evil! ask Barry Kelly why.} // -- somewhere else, after a long time, a user clicks // a resume button, and the thread resumes: -- if Terminated then exit; // leave TThread.Execute. // Not terminated, so we continue.. GrabResources; end; end; end; </code></pre> <p>The original answer vaguely suggests "TMutex, TEvent and critical sections".</p> <p>I guess I'm looking for a TThreadThatDoesntSuck.</p> <p>Here's the sample TThread derivative with a Win32Event, for comments:</p> <pre><code>unit SignalThreadUnit; interface uses Classes,SysUtils,Windows; type TSignalThread = class(TThread) protected FEventHandle:THandle; FWaitTime :Cardinal; {how long to wait for signal} //FCritSec:TCriticalSection; { critical section to prevent race condition at time of change of Signal states.} FOnWork:TNotifyEvent; FWorkCounter:Cardinal; { how many times have we been signalled } procedure Execute; override; { final; } //constructor Create(CreateSuspended: Boolean); { hide parent } public constructor Create; destructor Destroy; override; function WaitForSignal:Boolean; { returns TRUE if signal received, false if not received } function Active:Boolean; { is there work going on? } property WorkCounter:Cardinal read FWorkCounter; { how many times have we been signalled } procedure Sync(AMethod: TThreadMethod); procedure Start; { replaces method from TThread } procedure Stop; { provides an alternative to deprecated Suspend method } property Terminated; {make visible} published property WaitTime :Cardinal read FWaitTime write FWaitTime; {how long to wait for signal} property OnWork:TNotifyEvent read FOnWork write FOnWork; end; implementation { TSignalThread } constructor TSignalThread.Create; begin inherited Create({CreateSuspended}true); // must create event handle first! FEventHandle := CreateEvent( {security} nil, {bManualReset} true, {bInitialState} false, {name} nil); FWaitTime := 10; end; destructor TSignalThread.Destroy; begin if Self.Suspended or Self.Terminated then CloseHandle(FEventHandle); inherited; end; procedure TSignalThread.Execute; begin // inherited; { not applicable here} while not Terminated do begin if WaitForSignal then begin Inc(FWorkCounter); if Assigned(FOnWork) then begin FOnWork(Self); end; end; end; OutputDebugString('TSignalThread shutting down'); end; { Active will return true when it is easily (instantly) apparent that we are not paused. If we are not active, it is possible we are paused, or it is possible we are in some in-between state. } function TSignalThread.Active: Boolean; begin result := WaitForSingleObject(FEventHandle,0)= WAIT_OBJECT_0; end; procedure TSignalThread.Start; begin SetEvent(FEventHandle); { when we are in a signalled state, we can do work} if Self.Suspended then inherited Start; end; procedure TSignalThread.Stop; begin ResetEvent(FEventHandle); end; procedure TSignalThread.Sync(AMethod: TThreadMethod); begin Synchronize(AMethod); end; function TSignalThread.WaitForSignal: Boolean; var ret:Cardinal; begin result := false; ret := WaitForSingleObject(FEventHandle,FWaitTime); if (ret=WAIT_OBJECT_0) then result := not Self.Terminated; end; end. </code></pre>
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      1. POWith what delphi Code should I replace my calls to deprecated TThread method Suspend?
      1. USJeroen Wiert Pluimers
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      1. POWith what delphi Code should I replace my calls to deprecated TThread method Suspend?
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    1. COFor a `TThreadThatDoesntSuck` you should have a look at the OmniThreadLibrary, http://otl.17slon.com
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      1. POWith what delphi Code should I replace my calls to deprecated TThread method Suspend?
      1. USmghie
    2. COWhat happens when the code that does "the thread resumes" (thread.Resume) before "Self.Suspend" occurs? What you actually want is a manual reset event which is set to unsignalled, wait for it where you would Suspend, and set the event where you would Resume. That way, you won't miss a Resume by Suspending too late.
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      1. POWith what delphi Code should I replace my calls to deprecated TThread method Suspend?
      1. USBarry Kelly
    3. COI think Barry's comment is pretty close to being my answer. I edited the question to show a sample implementation of a 'suspend-less' way of pausing (blocking) a thread until I want it to use up some CPU time again. Basically I want a "start" and "stop" abstraction. The thread should never terminate until the application is ending, and we are cleaning up.
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      1. POWith what delphi Code should I replace my calls to deprecated TThread method Suspend?
      1. USWarren P
 

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