X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fmain.c;h=f7b3c7c84d1add69c1114e89f81ac4911490b33d;hb=a0e4ba18a275734e0934ba4d8d598bbcec7d52bb;hp=3feb3298927218354ea6e8d0974d46499f325ee6;hpb=25258405ed9590fcbcfb02c10dd8c018dba3a7bd;p=lttng-tools.git diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c index 3feb32989..f7b3c7c84 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 5 -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) @@ -513,15 +547,9 @@ static void sessiond_cleanup(void) */ utils_close_pipe(thread_quit_pipe); - /* - * If config.pid_file_path.value is undefined, the default file will be - * wiped when removing the rundir. - */ - if (config.pid_file_path.value) { - ret = remove(config.pid_file_path.value); - if (ret < 0) { - PERROR("remove pidfile %s", config.pid_file_path.value); - } + ret = remove(config.pid_file_path.value); + if (ret < 0) { + PERROR("remove pidfile %s", config.pid_file_path.value); } DBG("Removing sessiond and consumerd content of directory %s", @@ -4286,8 +4314,6 @@ 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"); @@ -4321,6 +4347,16 @@ static void *thread_manage_clients(void *data) 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)) { @@ -4853,8 +4889,8 @@ 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') { @@ -5446,15 +5482,6 @@ 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; @@ -5519,6 +5546,12 @@ 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. * @@ -5533,9 +5566,6 @@ 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 @@ -5811,12 +5841,6 @@ 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();