Multhreading: Watierall n'attend pas comme prévu

Question

J'ai un fil qui appelle deux threads distincts pour faire un peu de poids.Chaque fois que l'un des travaux est terminé un waihandle.set (0 est appelé et à la fin du fil de travailleur parent, je voulais servir pour être terminé, avant de continuer. Mais Pricea () est toujours à venir d'abord, puis().

new Thread(() =>
                           {
                               new Thread(() =>
                               {
                                   PriceA = _service.GetPriceA();
                                   _waithandle[0].Set();
                               }).Start();

                               new Thread(() =>
                               {
                                   PriceB = _service.GetPriceB();
                                   _waithandle[1].Set();
                               }).Start();

                               WaitHandle.WaitAll(_waithandle);
                           }).Start();
Console.WriteLine("Hello");

Qu'est-ce que je manque?

mise à jour:

private EventWaitHandle[] _waithandle;

CTOR:

 _waithandle[0] = new ManualResetEvent(false);
 _waithandle[1] = new ManualResetEvent(false);

Answer 1

new Thread(() =>
                           {
                               new Thread(() =>
                               {
                                   _priceA = _service.GetPriceA();
                                   _waithandle[0].Set();
                               }).Start();

                               new Thread(() =>
                               {
                                   _priceB = _service.GetPriceB();
                                   _waithandle[1].Set();
                               }).Start();

                               WaitHandle.WaitAll(_waithandle);
                               PriceA = _priceA;
                               PriceB = _priceB;
                           }).Start();

This did the job for me. Culprit was the INotifyChangedProperty() of the PriceA and PriceB which updated the UI too early making my waitall redundant. In case someone else has a similar issue...

Answer 2

You're creating a separate thread to wait... but the code after the statement you've given will continue because you're not waiting in that thread. In other words, you're creating three threads:

• Thread X: Creates threads A and B, then waits for them to finish
• Thread A: Gets PriceA and then sets waitHandle[0]
• Thread B: Gets PriceB and then sets waitHandle[1]

But thread X is doing nothing after it's waited, so what's the point of waiting within it?

Additionally, it would be a lot simpler to just call Join on the extra threads that you've created. In fact, if you only need to wait in the "current" thread, you only need one extra thread in the first place:

Thread t = new Thread(() => { PriceA = _service.GetPriceA(); });
t.Start();
PriceB = _service.GetPriceB();
t.Join();
// Other code

By the time you reach "other code", both PriceA and PriceB will have been set. Of course, this is missing a considerable amount of error handling... but that's easier to add when you've got a simpler starting point than your currently over-complicated code.

Answer 3

Are you resetting correctly the _waithandle[0] and [1]? For example:

_waithandle[0] = new ManualResetEvent(false);
_waithandle[1] = new ManualResetEvent(false);