X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fmain.c;h=88877c700437d54713020f4dc06c66f543fe4d67;hb=56c170703d909f138d941d44a2525f000d45ebf1;hp=5019b1c9c69a9e50c0d2dd0ccd1c2cf630f5ca20;hpb=ac00323072d53fcd0e32995163c5db4ef315c932;p=lttng-tools.git diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c index 5019b1c9c..88877c700 100644 --- a/src/bin/lttng-sessiond/main.c +++ b/src/bin/lttng-sessiond/main.c @@ -286,13 +286,39 @@ struct notification_thread_handle *notification_thread_handle; struct lttng_ht *agent_apps_ht_by_sock = NULL; /* - * Whether sessiond is ready for commands/notification channel/health check + * The initialization of the session daemon is done in multiple phases. + * + * While all threads are launched near-simultaneously, only some of them + * are needed to ensure the session daemon can start to respond to client * requests. - * NR_LTTNG_SESSIOND_READY must match the number of calls to - * sessiond_notify_ready(). + * + * There are two important guarantees that we wish to offer with respect + * to the initialisation of the session daemon: + * - When the daemonize/background launcher process exits, the sessiond + * is fully able to respond to client requests, + * - Auto-loaded sessions are visible to clients. + * + * In order to achieve this, a number of support threads have to be launched + * to allow the "client" thread to function properly. Moreover, since the + * "load session" thread needs the client thread, we must provide a way + * for the "load session" thread to know that the "client" thread is up + * and running. + * + * Hence, the support threads decrement the lttng_sessiond_ready counter + * while the "client" threads waits for it to reach 0. Once the "client" thread + * unblocks, it posts the message_thread_ready semaphore which allows the + * "load session" thread to progress. + * + * This implies that the "load session" thread is the last to be initialized + * and will explicitly call sessiond_signal_parents(), which signals the parents + * that the session daemon is fully initialized. + * + * The three (3) support threads are: + * - agent_thread + * - notification_thread + * - health_thread */ -#define NR_LTTNG_SESSIOND_READY 4 -int lttng_sessiond_ready = NR_LTTNG_SESSIOND_READY; +int lttng_sessiond_ready = 3; int sessiond_check_thread_quit_pipe(int fd, uint32_t events) { @@ -301,28 +327,36 @@ int sessiond_check_thread_quit_pipe(int fd, uint32_t events) /* Notify parents that we are ready for cmd and health check */ LTTNG_HIDDEN -void sessiond_notify_ready(void) +void sessiond_signal_parents(void) { - if (uatomic_sub_return(<tng_sessiond_ready, 1) == 0) { - /* - * Notify parent pid that we are ready to accept command - * for client side. This ppid is the one from the - * external process that spawned us. - */ - if (config.sig_parent) { - kill(ppid, SIGUSR1); - } + /* + * Notify parent pid that we are ready to accept command + * for client side. This ppid is the one from the + * external process that spawned us. + */ + if (config.sig_parent) { + kill(ppid, SIGUSR1); + } - /* - * Notify the parent of the fork() process that we are - * ready. - */ - if (config.daemonize || config.background) { - kill(child_ppid, SIGUSR1); - } + /* + * Notify the parent of the fork() process that we are + * ready. + */ + if (config.daemonize || config.background) { + kill(child_ppid, SIGUSR1); } } +LTTNG_HIDDEN +void sessiond_notify_ready(void) +{ + /* + * The _return variant is used since the implied memory barriers are + * required. + */ + (void) uatomic_sub_return(<tng_sessiond_ready, 1); +} + static int __sessiond_set_thread_pollset(struct lttng_poll_event *events, size_t size, int *a_pipe) @@ -4286,13 +4320,50 @@ static void *thread_manage_clients(void *data) goto error; } - sessiond_notify_ready(); ret = sem_post(&load_info->message_thread_ready); if (ret) { PERROR("sem_post message_thread_ready"); goto error; } + /* + * Wait until all support threads are initialized before accepting + * commands. + */ + while (uatomic_read(<tng_sessiond_ready) != 0) { + fd_set read_fds; + struct timeval timeout; + + FD_ZERO(&read_fds); + FD_SET(thread_quit_pipe[0], &read_fds); + memset(&timeout, 0, sizeof(timeout)); + timeout.tv_usec = 1000; + + /* + * If a support thread failed to launch, it may signal that + * we must exit and the sessiond would never be marked as + * "ready". + * + * The timeout is set to 1ms, which serves as a way to + * pace down this check. + */ + ret = select(thread_quit_pipe[0] + 1, &read_fds, NULL, NULL, + &timeout); + if (ret > 0 || (ret < 0 && errno != EINTR)) { + goto exit; + } + } + /* + * This barrier is paired with the one in sessiond_notify_ready() to + * ensure that loads accessing data initialized by the other threads, + * on which this thread was waiting, are not performed before this point. + * + * Note that this could be a 'read' memory barrier, but a full barrier + * is used in case the code changes. The performance implications of + * this choice are minimal since this is a slow path. + */ + cmm_smp_mb(); + /* This testpoint is after we signal readiness to the parent. */ if (testpoint(sessiond_thread_manage_clients)) { goto error; @@ -4824,8 +4895,8 @@ static int set_option(int opt, const char *arg, const char *optname) ERR("Port overflow in --agent-tcp-port parameter: %s", arg); return -1; } - config.agent_tcp_port = (uint32_t) v; - DBG3("Agent TCP port set to non default: %u", config.agent_tcp_port); + config.agent_tcp_port.begin = config.agent_tcp_port.end = (int) v; + DBG3("Agent TCP port set to non default: %i", (int) v); } } else if (string_match(optname, "load") || opt == 'l') { if (!arg || *arg == '\0') { @@ -5417,15 +5488,6 @@ static int write_pidfile(void) return utils_create_pid_file(getpid(), config.pid_file_path.value); } -/* - * Write agent TCP port using the rundir. - */ -static int write_agent_port(void) -{ - return utils_create_pid_file(config.agent_tcp_port, - config.agent_port_file_path.value); -} - static int set_clock_plugin_env(void) { int ret = 0; @@ -5490,6 +5552,12 @@ int main(int argc, char **argv) goto exit_set_signal_handler; } + /* + * Init config from environment variables. + * Command line option override env configuration per-doc. Do env first. + */ + sessiond_config_apply_env_config(&config); + /* * Parse arguments and load the daemon configuration file. * @@ -5504,9 +5572,6 @@ int main(int argc, char **argv) goto exit_options; } - /* Init config from environment variables. */ - sessiond_config_apply_env_config(&config); - /* * Resolve all paths received as arguments, configuration option, or * through environment variable as absolute paths. This is necessary @@ -5782,12 +5847,6 @@ int main(int argc, char **argv) retval = -1; goto exit_init_data; } - ret = write_agent_port(); - if (ret) { - ERR("Error in write_agent_port"); - retval = -1; - goto exit_init_data; - } /* Initialize communication library */ lttcomm_init();