diff --git a/app/src/server.c b/app/src/server.c index 77978d19..bea6fe98 100644 --- a/app/src/server.c +++ b/app/src/server.c @@ -318,14 +318,12 @@ connect_to_server(uint16_t port, uint32_t attempts, uint32_t delay) { } static void -close_socket(socket_t *socket) { - assert(*socket != INVALID_SOCKET); - net_shutdown(*socket, SHUT_RDWR); - if (!net_close(*socket)) { +close_socket(socket_t socket) { + assert(socket != INVALID_SOCKET); + net_shutdown(socket, SHUT_RDWR); + if (!net_close(socket)) { LOGW("Could not close socket"); - return; } - *socket = INVALID_SOCKET; } void @@ -337,6 +335,14 @@ static int run_wait_server(void *data) { struct server *server = data; cmd_simple_wait(server->process, NULL); // ignore exit code + // no need for synchronization, server_socket is initialized before this + // thread was created + if (server->server_socket != INVALID_SOCKET + && SDL_AtomicCAS(&server->server_socket_closed, 0, 1)) { + // On Linux, accept() is unblocked by shutdown(), but on Windows, it is + // unblocked by closesocket(). Therefore, call both (close_socket()). + close_socket(server->server_socket); + } LOGD("Server terminated"); return 0; } @@ -367,6 +373,12 @@ server_start(struct server *server, const char *serial, goto error2; } + // If the server process dies before connecting to the server socket, then + // the client will be stuck forever on accept(). To avoid the problem, we + // must be able to wake up the accept() call when the server dies. To keep + // things simple and multiplatform, just spawn a new thread waiting for the + // server process and calling shutdown()/close() on the server socket if + // necessary to wake up any accept() blocking call. server->wait_server_thread = SDL_CreateThread(run_wait_server, "wait-server", server); if (!server->wait_server_thread) { @@ -383,7 +395,9 @@ server_start(struct server *server, const char *serial, error2: if (!server->tunnel_forward) { - close_socket(&server->server_socket); + // the wait server thread is not started, SDL_AtomicSet() is sufficient + SDL_AtomicSet(&server->server_socket_closed, 1); + close_socket(server->server_socket); } disable_tunnel(server); error1: @@ -406,7 +420,11 @@ server_connect_to(struct server *server) { } // we don't need the server socket anymore - close_socket(&server->server_socket); + if (SDL_AtomicCAS(&server->server_socket_closed, 0, 1)) { + // close it from here + close_socket(server->server_socket); + // otherwise, it is closed by run_wait_server() + } } else { uint32_t attempts = 100; uint32_t delay = 100; // ms @@ -433,14 +451,15 @@ server_connect_to(struct server *server) { void server_stop(struct server *server) { - if (server->server_socket != INVALID_SOCKET) { - close_socket(&server->server_socket); + if (server->server_socket != INVALID_SOCKET + && SDL_AtomicCAS(&server->server_socket_closed, 0, 1)) { + close_socket(server->server_socket); } if (server->video_socket != INVALID_SOCKET) { - close_socket(&server->video_socket); + close_socket(server->video_socket); } if (server->control_socket != INVALID_SOCKET) { - close_socket(&server->control_socket); + close_socket(server->control_socket); } assert(server->process != PROCESS_NONE); diff --git a/app/src/server.h b/app/src/server.h index 050f7f01..79db72e5 100644 --- a/app/src/server.h +++ b/app/src/server.h @@ -3,6 +3,7 @@ #include #include +#include #include #include "config.h" @@ -14,6 +15,7 @@ struct server { char *serial; process_t process; SDL_Thread *wait_server_thread; + SDL_atomic_t server_socket_closed; socket_t server_socket; // only used if !tunnel_forward socket_t video_socket; socket_t control_socket; @@ -27,6 +29,7 @@ struct server { .serial = NULL, \ .process = PROCESS_NONE, \ .wait_server_thread = NULL, \ + .server_socket_closed = {0}, \ .server_socket = INVALID_SOCKET, \ .video_socket = INVALID_SOCKET, \ .control_socket = INVALID_SOCKET, \