Need a SignalAndWaitAll

Question

Hi All I am trying to write code to sync between processes. Here is the piece of code: setSignal(); // signal me (WaitHandle) first if (!WaitHandle.WaitAll(mWaitHandles timeout_ms true)) // mWaitHandles is an array of named event handles { mLog.WriteLine(While wait for sync it's timed out.); // better not reach here so timeout_ms should be big } resetSignal(); // reset WaitHandle My problem is that because setSignal() and WaitHandle.WaitAll() is not atomic other processes could have reset Signal before I enter WaitAll() then I have a deadlock or timeout. So I need a SignalAndWait() similar method SignalAndWaitAll(). Is there such construct? If not can I create one? Thanks for your consideration.

H Xia · Answer

Hi all Considering there is no such construct will the following code work for such scenario? Assume all the event handle instances are validly constructed and the thread is started properly. public sealed class X : CriticalFinalizerObject IDisposable { EventWaitHandle mEWH = null; // WaitHandle created by this instance // the following two fields pair each other WaitHandle[] mWaitHandles = null; // WaitHandles created by other instances string[] mEventName4WaitHandles = null; // EventName for WaitHandles created by other instances // using thread to reset signal bool mRunPostSetSignalThread = true; // event to signal setSignal myself EventWaitHandle mEWH4PostSetSignal = null; ... static void PostSetSignalThreadFunc(Object state) { for (; mRunPostSetSignalThread; mEWH4PostSetSignal.Reset()) { mEWH4PostSetSignal.WaitOne(); Thread.Sleep(1); // switch context to make sure the main thread entering wait state // is there any way to know whether the main thread is in waiting status? mEWH.Set(); } } public void synchronize(int timeout_ms) { while (mEWH4PostSetSignal.WaitOne(0 false)) { mLog.WriteLine(mEWH4PostSetSignal needs to signal but it's already in signaled state.); // should not reach here so timeout_ms should be big Thread.Sleep(1); // should not be here. Just let other threads run so mEWH4PostSetSignal is reset. } mEWH4PostSetSignal.Set(); // post setSignal() to make sure entering WaitAll before _SinglePCSync signaled // we always try to guarantee that the WaitAll is done before self is signaled. if (!WaitHandle.WaitAll(mWaitHandles timeout_ms true)) { mLog.WriteLine(While wait for sync it's timed out.); // better not reach here so timeout_ms should be big } Thread.Sleep(1); // Just let other threads run ahead of resetSignal. while (!mEWH.WaitOne(0 false)) // make sure mEWH is set before we reset it { mLog.WriteLine(mEWH needs to reset signal but it's already in reset state.); // better not reach here so timeout_ms should be big Thread.Sleep(1); // normally it should not be here } mEWH.Reset(); } }

H Xia · Answer

Thank you for the reply. Unfortunately what I need is the sync between processes. Monitor is just as far as I know CriticalSection it's valid only in a process.

Roei Bar · Answer

if you are using multiple Threads you can use insted the Threading.Monitor Class here is a sample: public void PrintNumbers() { Monitor.Enter( this ); try { for ( int i = 0 ; i 5 ; i++) { Thread.Sleep( 100 ); Console.Write(i +   ); } Console.WriteLine(); } finally { Monitor.Exit( this ); } } this will alow you todo sync with locks in place Monitor.Wait/Pulse/PulseAll can be used insted of the primitive WaitforSignal Monitor.Wait atomically releases the lock and waits reacquiring the lock before it returns