thor: Don't launch gdbserver more than once if servers die

kernel/thor/generic/gdbserver.cpp

@@ -440,24 +440,29 @@ coroutine<frg::expected<ProtocolError>> GdbServer::handleRequest_() {
 
 } // anonymous namespace
 
+static bool launched = false;
+
 void launchGdbServer(smarter::shared_ptr<Thread, ActiveHandle> thread,
 		frg::string_view path, smarter::shared_ptr<WorkQueue> wq) {
-	auto channel = solicitIoChannel("kernel-gdbserver");
-	if(!channel) {
-		infoLogger() << "thor: No I/O channel available for gdbserver" << frg::endlog;
-		return;
+	if(!launched) {
+		launched = true;
+		auto channel = solicitIoChannel("kernel-gdbserver");
+		if(!channel) {
+			infoLogger() << "thor: No I/O channel available for gdbserver" << frg::endlog;
+			return;
+		}
+		infoLogger() << "thor: Launching gdbserver on I/O channel "
+				<< channel->descriptiveTag() << frg::endlog;
+
+		auto svr = frg::construct<GdbServer>(*kernelAlloc,
+				std::move(thread), path, std::move(channel), std::move(wq));
+		async::detach_with_allocator(*kernelAlloc,
+			async::transform(svr->run(), [] (auto outcome) {
+				if(!outcome)
+					infoLogger() << "thor: Internal error in gdbserver" << frg::endlog;
+			})
+		);
 	}
-	infoLogger() << "thor: Launching gdbserver on I/O channel "
-			<< channel->descriptiveTag() << frg::endlog;
-
-	auto svr = frg::construct<GdbServer>(*kernelAlloc,
-			std::move(thread), path, std::move(channel), std::move(wq));
-	async::detach_with_allocator(*kernelAlloc,
-		async::transform(svr->run(), [] (auto outcome) {
-			if(!outcome)
-				infoLogger() << "thor: Internal error in gdbserver" << frg::endlog;
-		})
-	);
 }
 
 } // namespace thor