[IO] only try syscall on Future::submit if it has no dependencies

emper/io/Future.hpp

@@ -164,12 +164,15 @@ class SendFuture : public Future {
 
 	void submit() {
 		if constexpr (emper::IO_TRY_SYSCALL) {
+			// Only try to complete using a syscall if we have no dependencies
+			if (!dependency) {
 				ssize_t res = ::send(fd, buf, len, offsetOrFlags | MSG_DONTWAIT);
 
 				if (res > -1 || (errno != EAGAIN && errno != EWOULDBLOCK)) {
 					complete(res > 0 ? res : -errno);
 				}
 			}
+		}
 
 		Future::submit();
 	}
@@ -186,12 +189,15 @@ class RecvFuture : public Future {
 
 	void submit() {
 		if constexpr (emper::IO_TRY_SYSCALL) {
+			// Only try to complete using a syscall if we have no dependencies
+			if (!dependency) {
 				ssize_t res = ::recv(fd, buf, len, offsetOrFlags | MSG_DONTWAIT);
 
 				if (res > -1 || (errno != EAGAIN && errno != EWOULDBLOCK)) {
 					complete(res > 0 ? res : -errno);
 				}
 			}
+		}
 
 		Future::submit();
 	}