diff options
Diffstat (limited to 'applause.c')
| -rw-r--r-- | applause.c | 99 |
1 files changed, 67 insertions, 32 deletions
@@ -42,7 +42,10 @@ #define CMD_SERVER_IP "127.0.0.1" #define CMD_SERVER_PORT 10000 -#define MAX(X,Y) ((X) > (Y) ? (X) : (Y)) +#define MAX(X,Y) ((X) > (Y) ? (X) : (Y)) + +#define likely(X) __builtin_expect((X), 1) +#define unlikely(X) __builtin_expect((X), 0) static jack_client_t *client = NULL; @@ -66,9 +69,10 @@ static applause_output_port *output_ports = NULL; /** Number of Applause output ports */ static int output_ports_count = DEFAULT_NUMBER_OF_OUTPUT_PORTS; -static sig_atomic_t interrupted = 0; +static lua_State *L_global = NULL; -static sig_atomic_t playback = 0; +static volatile sig_atomic_t interrupted = 0; +static volatile sig_atomic_t playback = 0; typedef struct applause_midi_port { jack_port_t *jack_port; @@ -132,14 +136,57 @@ svsem_free(int id) } /** - * Handler for SIGINT, SIGUSR1 and SIGUSR2 signals. + * Can be called from Lua code to check the interruption-flag, + * ie. to detect SIGINT and CTRL+C interruptions. * - * SIGINT is delivered e.g. when the user presses - * CTRL+C. - * It sets `interrupted` which is polled in the Lua play() - * method which allows us to interrupt long (possibly infinite) - * sound playback. + * We do not simply expose the interrupted flag since LuaJIT + * does not support volatile variables and we cannot guarantee that + * the read is not optimized away. + * On the other hand, this function cannot raise a Lua error + * (and C functions via the classic C API are slow), so there is + * another wrapper in applause.lua. + */ +int +applause_is_interrupted(void) +{ + if (likely(!interrupted)) + return 0; + + interrupted = 0; + lua_sethook(L_global, NULL, 0, 0); + return 1; +} + +static void +signal_hook(lua_State *L, lua_Debug *ar) +{ + interrupted = 0; + lua_sethook(L, NULL, 0, 0); + + /* Avoid luaL_error -- a C hook doesn't add an extra frame. */ + luaL_where(L, 0); + lua_pushfstring(L, "%sinterrupted!", lua_tostring(L, -1)); + lua_error(L); +} + +static inline void +applause_interrupt(void) +{ + /* + * This should raise a Lua error via the hook ASAP. + * Unfortunetely, this cannot work reliably with JIT compilation + * enabled (see also https://luajit.org/faq.html#ctrlc). + * We therefore also set an interrupted flag that can be polled + * efficiently in tight loops. + */ + interrupted = 1; + lua_sethook(L_global, signal_hook, LUA_MASKCALL | LUA_MASKRET | LUA_MASKCOUNT, 1); +} + +/** + * Handler for SIGINT, SIGUSR1 and SIGUSR2 signals. * + * SIGINT is delivered e.g. when the user presses CTRL+C. * SIGUSR1 and SIGUSR2 are sent by parent to child * clients in order to control playback. */ @@ -147,7 +194,7 @@ static void signal_handler(int signum) { switch (signum) { - case SIGINT: interrupted = 1; break; + case SIGINT: applause_interrupt(); break; case SIGUSR1: playback = 1; break; case SIGUSR2: playback = 0; break; } @@ -415,17 +462,12 @@ applause_push_sample(int output_port_id, double sample_double) jack_default_audio_sample_t sample = (jack_default_audio_sample_t)sample_double; - if (interrupted) { - interrupted = 0; - return APPLAUSE_AUDIO_INTERRUPTED; - } - /* * NOTE: The alternative to reporting invalid port Ids here * would be exporting output_ports_count, so the Lua code can * check it and assert()ing here instead. */ - if (output_port_id < 1 || output_port_id > output_ports_count) + if (unlikely(output_port_id < 1 || output_port_id > output_ports_count)) return APPLAUSE_AUDIO_INVALID_PORT; port = output_ports + output_port_id - 1; @@ -441,7 +483,7 @@ applause_push_sample(int output_port_id, double sample_double) jack_ringbuffer_write(port->buffer, (const char *)&sample, sizeof(sample)); - if (port->buffer_xrun) { + if (unlikely(port->buffer_xrun)) { port->buffer_xrun = 0; return APPLAUSE_AUDIO_XRUN; } @@ -625,8 +667,8 @@ static pthread_mutex_t lua_mutex = PTHREAD_MUTEX_INITIALIZER; /** * Thread monitoring the client file desciptor. - * This will set the interrupted flag if the remote - * end closes its write part of the socket. + * This will raise interrupt the current Lua script if the remote + * end closes its write part of the socket (just like SIGINT would). * That's why we need the length header at the beginning * of requests. * There seems to be no easy way to find out whether the @@ -653,7 +695,7 @@ monitor_thread_cb(void *user_data) while (poll(&pfd, 1, -1) != 1 || !(pfd.revents & (POLLRDHUP | POLLERR | POLLHUP))); - interrupted = 1; + applause_interrupt(); return NULL; } @@ -741,9 +783,9 @@ command_server(void *user_data) pthread_mutex_lock(&lua_mutex); /* - * Start another thread monitoring client_fd and setting - * the interrupted flag in case the remote end terminates - * prematurely. This has the effect of ^C in SciTECO interrupting + * Start another thread monitoring client_fd for raising SIGINT + * in case the remote end terminates prematurely. + * This has the effect of ^C in SciTECO interrupting * the current command (e.g. play()) at least when using * socat (see monitor_thread_cb()). * A monitoring thread is started instead of running do_command() @@ -773,7 +815,7 @@ command_server(void *user_data) /* * FIXME: It would be nice to catch broken sockets * (e.g. waiting for play() has been interrupted), in order - * to set the interrupted flag. + * to raise SIGINT. * However it seems we'd need another thread for that running * do_command(), so we can select() the fd and eventually * join the thread. @@ -855,13 +897,6 @@ main(int argc, char **argv) } } - /* - * Register sigint_handler() as the SIGINT handler. - * This sets `interrupted`. Currently this is only polled - * in the Lua play() method in order to interrupt long - * sound playing. - * Otherwise it is ignored. - */ memset(&signal_action, 0, sizeof(signal_action)); signal_action.sa_handler = signal_handler; sigaction(SIGINT, &signal_action, NULL); @@ -871,7 +906,7 @@ main(int argc, char **argv) signal_action.sa_handler = SIG_IGN; sigaction(SIGPIPE, &signal_action, NULL); - L = luaL_newstate(); + L = L_global = luaL_newstate(); if (!L) { fprintf(stderr, "Error creating Lua state.\n"); exit(EXIT_FAILURE); |