Adhoc: Fix shutdown hanging when it comes right after adhoc init

The friend finder thread set friendFinderRunning itself, after a DNS
lookup of the adhoc server. A shutdown in that window cleared the flag
first; the thread then set it again, looped forever, and the join in
NetAdhocctl_Term() never returned. Gods Eater Burst hit this in about one
headless run in six. The flag is now set before the thread is created,
and a finished thread is joined before a new one replaces it, which
would otherwise call std::terminate.

The built-in adhoc server thread had the same race, behind its check for
an existing server, and gets the same fix.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

Core/HLE/proAdhoc.cpp

@@ -1401,8 +1401,7 @@ int friendFinder() {
 	}
 	g_adhocServerIP.in.sin_port = htons(SERVER_PORT);
 
-	// Finder Loop
-	friendFinderRunning = true;
+	// Finder Loop. The flag was set by whoever started us, and cleared to stop us.
 	while (friendFinderRunning) {
 		// Acquire Network Lock
 		//_acquireNetworkLock();

Core/HLE/proAdhocServer.cpp

@@ -1865,9 +1865,7 @@ int create_listen_socket(uint16_t port)
  */
 int server_loop(int server)
 {
-	// Set Running Status
-	//_status = 1;
-	adhocServerRunning = true;
+	// adhocServerRunning was set by whoever started the thread, and is cleared to stop it.
 
 	// Create Empty Status Logfile
 	update_status();

Core/HLE/sceNetAdhoc.cpp

@@ -1921,9 +1921,14 @@ void __NetAdhocInit() {
 	__AdhocNotifInit();
 	__AdhocServerInit();
 
-	// Create built-in AdhocServer Thread
+	// Create built-in AdhocServer Thread. The flag is set here rather than by the thread, so that a
+	// shutdown that clears it before the thread gets going can't be undone (see friendFinder).
 	adhocServerRunning = false;
+	if (adhocServerThread.joinable()) {
+		adhocServerThread.join();
+	}
 	if (g_Config.bEnableWlan && g_Config.bEnableAdhocServer) {
+		adhocServerRunning = true;
 		adhocServerThread = std::thread(proAdhocServerThread, SERVER_PORT);
 	}
 }
@@ -2008,6 +2013,12 @@ int sceNetAdhocctlInit(int stackSize, int prio, u32 productAddr) {
 
 	// TODO: Merging friendFinder (real) thread to AdhocThread (fake) thread on PSP side
 	if (!friendFinderRunning) {
+		// Set before the thread starts, not by it: shutting down before it got going used to clear
+		// the flag first, and then the thread set it again and never stopped, hanging the join.
+		if (friendFinderThread.joinable()) {
+			friendFinderThread.join();
+		}
+		friendFinderRunning = true;
 		friendFinderThread = std::thread(friendFinder);
 	}