Async: Add atomic pending flags to avoid multiple invocations of wake…

…up in the same loop iteration

This was an issue on windows, where we would get multiple entries in the kernel queue, due to  PostQueuedCompletionStatus being called multiple times.

Libraries/Async/Async.cpp

@@ -269,7 +269,16 @@ SC::Result SC::AsyncEventLoop::createAsyncTCPSocket(SocketFlags::AddressFamily f
     return associateExternallyCreatedTCPSocket(outDescriptor);
 }
 
-SC::Result SC::AsyncEventLoop::wakeUpFromExternalThread() { return internalSelf.wakeUpFromExternalThread(); }
+SC::Result SC::AsyncEventLoop::wakeUpFromExternalThread()
+{
+    if (not privateSelf.wakeUpPending.exchange(true))
+    {
+        // This executes if current thread is lucky enough to atomically exchange pending from false to true.
+        // This effectively allows coalescing calls from different threads into a single notification.
+        return internalSelf.wakeUpFromExternalThread();
+    }
+    return Result(true);
+}
 
 SC::Result SC::AsyncEventLoop::associateExternallyCreatedTCPSocket(SocketDescriptor& outDescriptor)
 {
@@ -851,9 +860,7 @@ SC::Result SC::AsyncEventLoop::wakeUpFromExternalThread(AsyncLoopWakeUp& async)
     AsyncLoopWakeUp& notifier = *static_cast<AsyncLoopWakeUp*>(&async);
     if (not notifier.pending.exchange(true))
     {
-        // This executes if current thread is lucky enough to atomically exchange pending from false to true.
-        // This effectively allows coalescing calls from different threads into a single notification.
-        SC_TRY(wakeUpFromExternalThread());
+        return wakeUpFromExternalThread();
     }
     return Result(true);
 }
@@ -879,6 +886,8 @@ void SC::AsyncEventLoop::Private::executeWakeUps(AsyncResult& result)
             notifier->pending.exchange(false); // allow executing the notification again
         }
     }
+
+    wakeUpPending.exchange(false);
 }
 
 void SC::AsyncEventLoop::Private::removeActiveHandle(AsyncRequest& async)

Libraries/Async/Internal/AsyncPrivate.h

@@ -8,6 +8,8 @@ struct SC::AsyncEventLoop::Private
 {
     AsyncEventLoop* eventLoop = nullptr;
 
+    Atomic<bool> wakeUpPending = false;
+
     int numberOfActiveHandles     = 0;
     int numberOfManualCompletions = 0;
     int numberOfExternals         = 0;