[deliverable/lttng-ust.git] / libust / lttng-ust-comm.c

/*
 * lttng-ust-comm.c
 *
 * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
 * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; only
 * version 2.1 of the License.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/prctl.h>
#include <unistd.h>
#include <errno.h>
#include <pthread.h>
#include <semaphore.h>
#include <time.h>
#include <assert.h>
#include <urcu/uatomic.h>

#include <lttng-ust-comm.h>
#include <ust/usterr-signal-safe.h>
#include <ust/lttng-ust-abi.h>
#include <ust/tracepoint.h>

/*
 * Has lttng ust comm constructor been called ?
 */
static int initialized;

/*
 * communication thread mutex. Held when handling a command, also held
 * by fork() to deal with removal of threads, and by exit path.
 */
static pthread_mutex_t lttng_ust_comm_mutex = PTHREAD_MUTEX_INITIALIZER;

/* Should the ust comm thread quit ? */
static int lttng_ust_comm_should_quit;

/*
 * Wait for either of these before continuing to the main
 * program:
 * - the register_done message from sessiond daemon
 *   (will let the sessiond daemon enable sessions before main
 *   starts.)
 * - sessiond daemon is not reachable.
 * - timeout (ensuring applications are resilient to session
 *   daemon problems).
 */
static sem_t constructor_wait;
/*
 * Doing this for both the global and local sessiond.
 */
static int sem_count = { 2 };

/*
 * Info about socket and associated listener thread.
 */
struct sock_info {
	const char *name;
	char sock_path[PATH_MAX];
	int socket;
	pthread_t ust_listener;	/* listener thread */
	int root_handle;
	int constructor_sem_posted;;
};

/* Socket from app (connect) to session daemon (listen) for communication */
struct sock_info global_apps = {
	.name = "global",
	.sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK,
	.socket = -1,
	.root_handle = -1,
};

/* TODO: allow global_apps_sock_path override */

struct sock_info local_apps = {
	.name = "local",
	.socket = -1,
	.root_handle = -1,
};

extern void ltt_ring_buffer_client_overwrite_init(void);
extern void ltt_ring_buffer_client_discard_init(void);
extern void ltt_ring_buffer_metadata_client_init(void);
extern void ltt_ring_buffer_client_overwrite_exit(void);
extern void ltt_ring_buffer_client_discard_exit(void);
extern void ltt_ring_buffer_metadata_client_exit(void);

static
int setup_local_apps_socket(void)
{
	const char *home_dir;

	home_dir = (const char *) getenv("HOME");
	if (!home_dir)
		return -ENOENT;
	snprintf(local_apps.sock_path, PATH_MAX,
		 DEFAULT_HOME_APPS_UNIX_SOCK, home_dir);
	return 0;
}

static
int register_app_to_sessiond(int socket)
{
	ssize_t ret;
	int prctl_ret;
	struct {
		uint32_t major;
		uint32_t minor;
		pid_t pid;
		pid_t ppid;
		uid_t uid;
		gid_t gid;
		char name[16];	/* process name */
	} reg_msg;

	reg_msg.major = LTTNG_UST_COMM_VERSION_MAJOR;
	reg_msg.minor = LTTNG_UST_COMM_VERSION_MINOR;
	reg_msg.pid = getpid();
	reg_msg.ppid = getppid();
	reg_msg.uid = getuid();
	reg_msg.gid = getgid();
	prctl_ret = prctl(PR_GET_NAME, (unsigned long) reg_msg.name, 0, 0, 0);
	if (prctl_ret) {
		ERR("Error executing prctl");
		return -errno;
	}

	ret = lttcomm_send_unix_sock(socket, &reg_msg, sizeof(reg_msg));
	if (ret >= 0 && ret != sizeof(reg_msg))
		return -EIO;
	return ret;
}

static
int send_reply(int sock, struct lttcomm_ust_reply *lur)
{
	ssize_t len;

	len = lttcomm_send_unix_sock(sock, lur, sizeof(*lur));
	switch (len) {
	case sizeof(*lur):
		DBG("message successfully sent");
		return 0;
	case -1:
		if (errno == ECONNRESET) {
			printf("remote end closed connection\n");
			return 0;
		}
		return -1;
	default:
		printf("incorrect message size: %zd\n", len);
		return -1;
	}
}

static
int handle_register_done(struct sock_info *sock_info)
{
	int ret;

	if (sock_info->constructor_sem_posted)
		return 0;
	sock_info->constructor_sem_posted = 1;
	ret = uatomic_add_return(&sem_count, -1);
	if (ret == 0) {
		ret = sem_post(&constructor_wait);
		assert(!ret);
	}
	return 0;
}

static
int handle_message(struct sock_info *sock_info,
		int sock, struct lttcomm_ust_msg *lum)
{
	int ret = 0;
	const struct objd_ops *ops;
	struct lttcomm_ust_reply lur;

	pthread_mutex_lock(&lttng_ust_comm_mutex);

	memset(&lur, 0, sizeof(lur));

	if (lttng_ust_comm_should_quit) {
		ret = -EPERM;
		goto end;
	}

	ops = objd_ops(lum->handle);
	if (!ops) {
		ret = -ENOENT;
		goto end;
	}

	switch (lum->cmd) {
	case LTTNG_UST_REGISTER_DONE:
		if (lum->handle == LTTNG_UST_ROOT_HANDLE)
			ret = handle_register_done(sock_info);
		else
			ret = -EINVAL;
		break;
	case LTTNG_UST_RELEASE:
		if (lum->handle == LTTNG_UST_ROOT_HANDLE)
			ret = -EPERM;
		else
			ret = objd_unref(lum->handle);
		break;
	default:
		if (ops->cmd)
			ret = ops->cmd(lum->handle, lum->cmd,
					(unsigned long) &lum->u);
		else
			ret = -ENOSYS;
		break;
	}

end:
	lur.handle = lum->handle;
	lur.cmd = lum->cmd;
	lur.ret_val = ret;
	if (ret >= 0) {
		lur.ret_code = LTTCOMM_OK;
	} else {
		lur.ret_code = LTTCOMM_SESSION_FAIL;
	}
	ret = send_reply(sock, &lur);

	pthread_mutex_unlock(&lttng_ust_comm_mutex);
	return ret;
}

static
void cleanup_sock_info(struct sock_info *sock_info)
{
	int ret;

	if (sock_info->socket != -1) {
		ret = close(sock_info->socket);
		if (ret) {
			ERR("Error closing local apps socket");
		}
		sock_info->socket = -1;
	}
	if (sock_info->root_handle != -1) {
		ret = objd_unref(sock_info->root_handle);
		if (ret) {
			ERR("Error unref root handle");
		}
		sock_info->root_handle = -1;
	}
}

/*
 * This thread does not allocate any resource, except within
 * handle_message, within mutex protection. This mutex protects against
 * fork and exit.
 * The other moment it allocates resources is at socket connexion, which
 * is also protected by the mutex.
 */
static
void *ust_listener_thread(void *arg)
{
	struct sock_info *sock_info = arg;
	int sock, ret;

	/* Restart trying to connect to the session daemon */
restart:
	pthread_mutex_lock(&lttng_ust_comm_mutex);

	if (lttng_ust_comm_should_quit) {
		pthread_mutex_unlock(&lttng_ust_comm_mutex);
		goto quit;
	}

	if (sock_info->socket != -1) {
		ret = close(sock_info->socket);
		if (ret) {
			ERR("Error closing %s apps socket", sock_info->name);
		}
		sock_info->socket = -1;
	}

	/* Check for sessiond availability with pipe TODO */

	/* Register */
	ret = lttcomm_connect_unix_sock(sock_info->sock_path);
	if (ret < 0) {
		ERR("Error connecting to %s apps socket", sock_info->name);
		/*
		 * If we cannot find the sessiond daemon, don't delay
		 * constructor execution.
		 */
		ret = handle_register_done(sock_info);
		assert(!ret);
		pthread_mutex_unlock(&lttng_ust_comm_mutex);
		sleep(5);
		goto restart;
	}

	sock_info->socket = sock = ret;

	/*
	 * Create only one root handle per listener thread for the whole
	 * process lifetime.
	 */
	if (sock_info->root_handle == -1) {
		ret = lttng_abi_create_root_handle();
		if (ret) {
			ERR("Error creating root handle");
			pthread_mutex_unlock(&lttng_ust_comm_mutex);
			goto quit;
		}
		sock_info->root_handle = ret;
	}

	ret = register_app_to_sessiond(sock);
	if (ret < 0) {
		ERR("Error registering to %s apps socket", sock_info->name);
		/*
		 * If we cannot register to the sessiond daemon, don't
		 * delay constructor execution.
		 */
		ret = handle_register_done(sock_info);
		assert(!ret);
		pthread_mutex_unlock(&lttng_ust_comm_mutex);
		sleep(5);
		goto restart;
	}
	pthread_mutex_unlock(&lttng_ust_comm_mutex);

	for (;;) {
		ssize_t len;
		struct lttcomm_ust_msg lum;

		len = lttcomm_recv_unix_sock(sock, &lum, sizeof(lum));
		switch (len) {
		case 0:	/* orderly shutdown */
			DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info->name);
			goto end;
		case sizeof(lum):
			DBG("message received\n");
			ret = handle_message(sock_info, sock, &lum);
			if (ret < 0) {
				ERR("Error handling message for %s socket", sock_info->name);
			}
			continue;
		case -1:
			if (errno == ECONNRESET) {
				ERR("%s remote end closed connection\n", sock_info->name);
				goto end;
			}
			goto end;
		default:
			ERR("incorrect message size (%s socket): %zd\n", sock_info->name, len);
			continue;
		}

	}
end:
	goto restart;	/* try to reconnect */
quit:
	return NULL;
}

/*
 * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
 */
static
int get_timeout(struct timespec *constructor_timeout)
{
	long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
	char *str_delay;
	int ret;

	str_delay = getenv("UST_REGISTER_TIMEOUT");
	if (str_delay) {
		constructor_delay_ms = strtol(str_delay, NULL, 10);
	}

	switch (constructor_delay_ms) {
	case -1:/* fall-through */
	case 0:
		return constructor_delay_ms;
	default:
		break;
	}

	/*
	 * If we are unable to find the current time, don't wait.
	 */
	ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
	if (ret) {
		return -1;
	}
	constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
	constructor_timeout->tv_nsec +=
		(constructor_delay_ms % 1000UL) * 1000000UL;
	if (constructor_timeout->tv_nsec >= 1000000000UL) {
		constructor_timeout->tv_sec++;
		constructor_timeout->tv_nsec -= 1000000000UL;
	}
	return 1;
}

/*
 * sessiond monitoring thread: monitor presence of global and per-user
 * sessiond by polling the application common named pipe.
 */
/* TODO */

void __attribute__((constructor)) lttng_ust_init(void)
{
	struct timespec constructor_timeout;
	int timeout_mode;
	int ret;

	if (uatomic_xchg(&initialized, 1) == 1)
		return;

	/*
	 * We want precise control over the order in which we construct
	 * our sub-libraries vs starting to receive commands from
	 * sessiond (otherwise leading to errors when trying to create
	 * sessiond before the init functions are completed).
	 */
	init_usterr();
	init_tracepoint();
	ltt_ring_buffer_metadata_client_init();
	ltt_ring_buffer_client_overwrite_init();
	ltt_ring_buffer_client_discard_init();

	timeout_mode = get_timeout(&constructor_timeout);

	ret = sem_init(&constructor_wait, 0, 0);
	assert(!ret);

	ret = setup_local_apps_socket();
	if (ret) {
		ERR("Error setting up to local apps socket");
	}

	ret = pthread_create(&global_apps.ust_listener, NULL,
			ust_listener_thread, &global_apps);
	ret = pthread_create(&local_apps.ust_listener, NULL,
			ust_listener_thread, &local_apps);

	switch (timeout_mode) {
	case 1:	/* timeout wait */
		do {
			ret = sem_timedwait(&constructor_wait,
					&constructor_timeout);
		} while (ret < 0 && errno == EINTR);
		if (ret < 0 && errno == ETIMEDOUT) {
			ERR("Timed out waiting for ltt-sessiond");
		} else {
			assert(!ret);
		}
		break;
	case -1:/* wait forever */
		do {
			ret = sem_wait(&constructor_wait);
		} while (ret < 0 && errno == EINTR);
		assert(!ret);
		break;
	case 0:	/* no timeout */
		break;
	}
}

void __attribute__((destructor)) lttng_ust_exit(void)
{
	int ret;

	/*
	 * Using pthread_cancel here because:
	 * A) we don't want to hang application teardown.
	 * B) the thread is not allocating any resource.
	 */

	/*
	 * Require the communication thread to quit. Synchronize with
	 * mutexes to ensure it is not in a mutex critical section when
	 * pthread_cancel is later called.
	 */
	pthread_mutex_lock(&lttng_ust_comm_mutex);
	lttng_ust_comm_should_quit = 1;
	pthread_mutex_unlock(&lttng_ust_comm_mutex);

	ret = pthread_cancel(global_apps.ust_listener);
	if (ret) {
		ERR("Error cancelling global ust listener thread");
	}

	cleanup_sock_info(&global_apps);

	ret = pthread_cancel(local_apps.ust_listener);
	if (ret) {
		ERR("Error cancelling local ust listener thread");
	}

	cleanup_sock_info(&local_apps);

	lttng_ust_abi_exit();
	ltt_events_exit();
	ltt_ring_buffer_client_discard_exit();
	ltt_ring_buffer_client_overwrite_exit();
	ltt_ring_buffer_metadata_client_exit();
	exit_tracepoint();
}
Commit	Line	Data
	1	/*
	2	* lttng-ust-comm.c
	3	*
	4	* Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
	5	* Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	6	*
	7	* This library is free software; you can redistribute it and/or
	8	* modify it under the terms of the GNU Lesser General Public
	9	* License as published by the Free Software Foundation; only
	10	* version 2.1 of the License.
	11	*
	12	* This library is distributed in the hope that it will be useful,
	13	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	15	* Lesser General Public License for more details.
	16	*
	17	* You should have received a copy of the GNU Lesser General Public
	18	* License along with this library; if not, write to the Free Software
	19	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	20	*/
	21
	22	#include <sys/types.h>
	23	#include <sys/socket.h>
	24	#include <sys/prctl.h>
	25	#include <unistd.h>
	26	#include <errno.h>
	27	#include <pthread.h>
	28	#include <semaphore.h>
	29	#include <time.h>
	30	#include <assert.h>
	31	#include <urcu/uatomic.h>
	32
	33	#include <lttng-ust-comm.h>
	34	#include <ust/usterr-signal-safe.h>
	35	#include <ust/lttng-ust-abi.h>
	36	#include <ust/tracepoint.h>
	37
	38	/*
	39	* Has lttng ust comm constructor been called ?
	40	*/
	41	static int initialized;
	42
	43	/*
	44	* communication thread mutex. Held when handling a command, also held
	45	* by fork() to deal with removal of threads, and by exit path.
	46	*/
	47	static pthread_mutex_t lttng_ust_comm_mutex = PTHREAD_MUTEX_INITIALIZER;
	48
	49	/* Should the ust comm thread quit ? */
	50	static int lttng_ust_comm_should_quit;
	51
	52	/*
	53	* Wait for either of these before continuing to the main
	54	* program:
	55	* - the register_done message from sessiond daemon
	56	* (will let the sessiond daemon enable sessions before main
	57	* starts.)
	58	* - sessiond daemon is not reachable.
	59	* - timeout (ensuring applications are resilient to session
	60	* daemon problems).
	61	*/
	62	static sem_t constructor_wait;
	63	/*
	64	* Doing this for both the global and local sessiond.
	65	*/
	66	static int sem_count = { 2 };
	67
	68	/*
	69	* Info about socket and associated listener thread.
	70	*/
	71	struct sock_info {
	72	const char *name;
	73	char sock_path[PATH_MAX];
	74	int socket;
	75	pthread_t ust_listener; /* listener thread */
	76	int root_handle;
	77	int constructor_sem_posted;;
	78	};
	79
	80	/* Socket from app (connect) to session daemon (listen) for communication */
	81	struct sock_info global_apps = {
	82	.name = "global",
	83	.sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK,
	84	.socket = -1,
	85	.root_handle = -1,
	86	};
	87
	88	/* TODO: allow global_apps_sock_path override */
	89
	90	struct sock_info local_apps = {
	91	.name = "local",
	92	.socket = -1,
	93	.root_handle = -1,
	94	};
	95
	96	extern void ltt_ring_buffer_client_overwrite_init(void);
	97	extern void ltt_ring_buffer_client_discard_init(void);
	98	extern void ltt_ring_buffer_metadata_client_init(void);
	99	extern void ltt_ring_buffer_client_overwrite_exit(void);
	100	extern void ltt_ring_buffer_client_discard_exit(void);
	101	extern void ltt_ring_buffer_metadata_client_exit(void);
	102
	103	static
	104	int setup_local_apps_socket(void)
	105	{
	106	const char *home_dir;
	107
	108	home_dir = (const char *) getenv("HOME");
	109	if (!home_dir)
	110	return -ENOENT;
	111	snprintf(local_apps.sock_path, PATH_MAX,
	112	DEFAULT_HOME_APPS_UNIX_SOCK, home_dir);
	113	return 0;
	114	}
	115
	116	static
	117	int register_app_to_sessiond(int socket)
	118	{
	119	ssize_t ret;
	120	int prctl_ret;
	121	struct {
	122	uint32_t major;
	123	uint32_t minor;
	124	pid_t pid;
	125	pid_t ppid;
	126	uid_t uid;
	127	gid_t gid;
	128	char name[16]; /* process name */
	129	} reg_msg;
	130
	131	reg_msg.major = LTTNG_UST_COMM_VERSION_MAJOR;
	132	reg_msg.minor = LTTNG_UST_COMM_VERSION_MINOR;
	133	reg_msg.pid = getpid();
	134	reg_msg.ppid = getppid();
	135	reg_msg.uid = getuid();
	136	reg_msg.gid = getgid();
	137	prctl_ret = prctl(PR_GET_NAME, (unsigned long) reg_msg.name, 0, 0, 0);
	138	if (prctl_ret) {
	139	ERR("Error executing prctl");
	140	return -errno;
	141	}
	142
	143	ret = lttcomm_send_unix_sock(socket, &reg_msg, sizeof(reg_msg));
	144	if (ret >= 0 && ret != sizeof(reg_msg))
	145	return -EIO;
	146	return ret;
	147	}
	148
	149	static
	150	int send_reply(int sock, struct lttcomm_ust_reply *lur)
	151	{
	152	ssize_t len;
	153
	154	len = lttcomm_send_unix_sock(sock, lur, sizeof(*lur));
	155	switch (len) {
	156	case sizeof(*lur):
	157	DBG("message successfully sent");
	158	return 0;
	159	case -1:
	160	if (errno == ECONNRESET) {
	161	printf("remote end closed connection\n");
	162	return 0;
	163	}
	164	return -1;
	165	default:
	166	printf("incorrect message size: %zd\n", len);
	167	return -1;
	168	}
	169	}
	170
	171	static
	172	int handle_register_done(struct sock_info *sock_info)
	173	{
	174	int ret;
	175
	176	if (sock_info->constructor_sem_posted)
	177	return 0;
	178	sock_info->constructor_sem_posted = 1;
	179	ret = uatomic_add_return(&sem_count, -1);
	180	if (ret == 0) {
	181	ret = sem_post(&constructor_wait);
	182	assert(!ret);
	183	}
	184	return 0;
	185	}
	186
	187	static
	188	int handle_message(struct sock_info *sock_info,
	189	int sock, struct lttcomm_ust_msg *lum)
	190	{
	191	int ret = 0;
	192	const struct objd_ops *ops;
	193	struct lttcomm_ust_reply lur;
	194
	195	pthread_mutex_lock(&lttng_ust_comm_mutex);
	196
	197	memset(&lur, 0, sizeof(lur));
	198
	199	if (lttng_ust_comm_should_quit) {
	200	ret = -EPERM;
	201	goto end;
	202	}
	203
	204	ops = objd_ops(lum->handle);
	205	if (!ops) {
	206	ret = -ENOENT;
	207	goto end;
	208	}
	209
	210	switch (lum->cmd) {
	211	case LTTNG_UST_REGISTER_DONE:
	212	if (lum->handle == LTTNG_UST_ROOT_HANDLE)
	213	ret = handle_register_done(sock_info);
	214	else
	215	ret = -EINVAL;
	216	break;
	217	case LTTNG_UST_RELEASE:
	218	if (lum->handle == LTTNG_UST_ROOT_HANDLE)
	219	ret = -EPERM;
	220	else
	221	ret = objd_unref(lum->handle);
	222	break;
	223	default:
	224	if (ops->cmd)
	225	ret = ops->cmd(lum->handle, lum->cmd,
	226	(unsigned long) &lum->u);
	227	else
	228	ret = -ENOSYS;
	229	break;
	230	}
	231
	232	end:
	233	lur.handle = lum->handle;
	234	lur.cmd = lum->cmd;
	235	lur.ret_val = ret;
	236	if (ret >= 0) {
	237	lur.ret_code = LTTCOMM_OK;
	238	} else {
	239	lur.ret_code = LTTCOMM_SESSION_FAIL;
	240	}
	241	ret = send_reply(sock, &lur);
	242
	243	pthread_mutex_unlock(&lttng_ust_comm_mutex);
	244	return ret;
	245	}
	246
	247	static
	248	void cleanup_sock_info(struct sock_info *sock_info)
	249	{
	250	int ret;
	251
	252	if (sock_info->socket != -1) {
	253	ret = close(sock_info->socket);
	254	if (ret) {
	255	ERR("Error closing local apps socket");
	256	}
	257	sock_info->socket = -1;
	258	}
	259	if (sock_info->root_handle != -1) {
	260	ret = objd_unref(sock_info->root_handle);
	261	if (ret) {
	262	ERR("Error unref root handle");
	263	}
	264	sock_info->root_handle = -1;
	265	}
	266	}
	267
	268	/*
	269	* This thread does not allocate any resource, except within
	270	* handle_message, within mutex protection. This mutex protects against
	271	* fork and exit.
	272	* The other moment it allocates resources is at socket connexion, which
	273	* is also protected by the mutex.
	274	*/
	275	static
	276	void ust_listener_thread(void arg)
	277	{
	278	struct sock_info *sock_info = arg;
	279	int sock, ret;
	280
	281	/* Restart trying to connect to the session daemon */
	282	restart:
	283	pthread_mutex_lock(&lttng_ust_comm_mutex);
	284
	285	if (lttng_ust_comm_should_quit) {
	286	pthread_mutex_unlock(&lttng_ust_comm_mutex);
	287	goto quit;
	288	}
	289
	290	if (sock_info->socket != -1) {
	291	ret = close(sock_info->socket);
	292	if (ret) {
	293	ERR("Error closing %s apps socket", sock_info->name);
	294	}
	295	sock_info->socket = -1;
	296	}
	297
	298	/* Check for sessiond availability with pipe TODO */
	299
	300	/* Register */
	301	ret = lttcomm_connect_unix_sock(sock_info->sock_path);
	302	if (ret < 0) {
	303	ERR("Error connecting to %s apps socket", sock_info->name);
	304	/*
	305	* If we cannot find the sessiond daemon, don't delay
	306	* constructor execution.
	307	*/
	308	ret = handle_register_done(sock_info);
	309	assert(!ret);
	310	pthread_mutex_unlock(&lttng_ust_comm_mutex);
	311	sleep(5);
	312	goto restart;
	313	}
	314
	315	sock_info->socket = sock = ret;
	316
	317	/*
	318	* Create only one root handle per listener thread for the whole
	319	* process lifetime.
	320	*/
	321	if (sock_info->root_handle == -1) {
	322	ret = lttng_abi_create_root_handle();
	323	if (ret) {
	324	ERR("Error creating root handle");
	325	pthread_mutex_unlock(&lttng_ust_comm_mutex);
	326	goto quit;
	327	}
	328	sock_info->root_handle = ret;
	329	}
	330
	331	ret = register_app_to_sessiond(sock);
	332	if (ret < 0) {
	333	ERR("Error registering to %s apps socket", sock_info->name);
	334	/*
	335	* If we cannot register to the sessiond daemon, don't
	336	* delay constructor execution.
	337	*/
	338	ret = handle_register_done(sock_info);
	339	assert(!ret);
	340	pthread_mutex_unlock(&lttng_ust_comm_mutex);
	341	sleep(5);
	342	goto restart;
	343	}
	344	pthread_mutex_unlock(&lttng_ust_comm_mutex);
	345
	346	for (;;) {
	347	ssize_t len;
	348	struct lttcomm_ust_msg lum;
	349
	350	len = lttcomm_recv_unix_sock(sock, &lum, sizeof(lum));
	351	switch (len) {
	352	case 0: /* orderly shutdown */
	353	DBG("%s ltt-sessiond has performed an orderly shutdown\n", sock_info->name);
	354	goto end;
	355	case sizeof(lum):
	356	DBG("message received\n");
	357	ret = handle_message(sock_info, sock, &lum);
	358	if (ret < 0) {
	359	ERR("Error handling message for %s socket", sock_info->name);
	360	}
	361	continue;
	362	case -1:
	363	if (errno == ECONNRESET) {
	364	ERR("%s remote end closed connection\n", sock_info->name);
	365	goto end;
	366	}
	367	goto end;
	368	default:
	369	ERR("incorrect message size (%s socket): %zd\n", sock_info->name, len);
	370	continue;
	371	}
	372
	373	}
	374	end:
	375	goto restart; /* try to reconnect */
	376	quit:
	377	return NULL;
	378	}
	379
	380	/*
	381	* Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
	382	*/
	383	static
	384	int get_timeout(struct timespec *constructor_timeout)
	385	{
	386	long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
	387	char *str_delay;
	388	int ret;
	389
	390	str_delay = getenv("UST_REGISTER_TIMEOUT");
	391	if (str_delay) {
	392	constructor_delay_ms = strtol(str_delay, NULL, 10);
	393	}
	394
	395	switch (constructor_delay_ms) {
	396	case -1:/* fall-through */
	397	case 0:
	398	return constructor_delay_ms;
	399	default:
	400	break;
	401	}
	402
	403	/*
	404	* If we are unable to find the current time, don't wait.
	405	*/
	406	ret = clock_gettime(CLOCK_REALTIME, constructor_timeout);
	407	if (ret) {
	408	return -1;
	409	}
	410	constructor_timeout->tv_sec += constructor_delay_ms / 1000UL;
	411	constructor_timeout->tv_nsec +=
	412	(constructor_delay_ms % 1000UL) * 1000000UL;
	413	if (constructor_timeout->tv_nsec >= 1000000000UL) {
	414	constructor_timeout->tv_sec++;
	415	constructor_timeout->tv_nsec -= 1000000000UL;
	416	}
	417	return 1;
	418	}
	419
	420	/*
	421	* sessiond monitoring thread: monitor presence of global and per-user
	422	* sessiond by polling the application common named pipe.
	423	*/
	424	/* TODO */
	425
	426	void __attribute__((constructor)) lttng_ust_init(void)
	427	{
	428	struct timespec constructor_timeout;
	429	int timeout_mode;
	430	int ret;
	431
	432	if (uatomic_xchg(&initialized, 1) == 1)
	433	return;
	434
	435	/*
	436	* We want precise control over the order in which we construct
	437	* our sub-libraries vs starting to receive commands from
	438	* sessiond (otherwise leading to errors when trying to create
	439	* sessiond before the init functions are completed).
	440	*/
	441	init_usterr();
	442	init_tracepoint();
	443	ltt_ring_buffer_metadata_client_init();
	444	ltt_ring_buffer_client_overwrite_init();
	445	ltt_ring_buffer_client_discard_init();
	446
	447	timeout_mode = get_timeout(&constructor_timeout);
	448
	449	ret = sem_init(&constructor_wait, 0, 0);
	450	assert(!ret);
	451
	452	ret = setup_local_apps_socket();
	453	if (ret) {
	454	ERR("Error setting up to local apps socket");
	455	}
	456
	457	ret = pthread_create(&global_apps.ust_listener, NULL,
	458	ust_listener_thread, &global_apps);
	459	ret = pthread_create(&local_apps.ust_listener, NULL,
	460	ust_listener_thread, &local_apps);
	461
	462	switch (timeout_mode) {
	463	case 1: /* timeout wait */
	464	do {
	465	ret = sem_timedwait(&constructor_wait,
	466	&constructor_timeout);
	467	} while (ret < 0 && errno == EINTR);
	468	if (ret < 0 && errno == ETIMEDOUT) {
	469	ERR("Timed out waiting for ltt-sessiond");
	470	} else {
	471	assert(!ret);
	472	}
	473	break;
	474	case -1:/* wait forever */
	475	do {
	476	ret = sem_wait(&constructor_wait);
	477	} while (ret < 0 && errno == EINTR);
	478	assert(!ret);
	479	break;
	480	case 0: /* no timeout */
	481	break;
	482	}
	483	}
	484
	485	void __attribute__((destructor)) lttng_ust_exit(void)
	486	{
	487	int ret;
	488
	489	/*
	490	* Using pthread_cancel here because:
	491	* A) we don't want to hang application teardown.
	492	* B) the thread is not allocating any resource.
	493	*/
	494
	495	/*
	496	* Require the communication thread to quit. Synchronize with
	497	* mutexes to ensure it is not in a mutex critical section when
	498	* pthread_cancel is later called.
	499	*/
	500	pthread_mutex_lock(&lttng_ust_comm_mutex);
	501	lttng_ust_comm_should_quit = 1;
	502	pthread_mutex_unlock(&lttng_ust_comm_mutex);
	503
	504	ret = pthread_cancel(global_apps.ust_listener);
	505	if (ret) {
	506	ERR("Error cancelling global ust listener thread");
	507	}
	508
	509	cleanup_sock_info(&global_apps);
	510
	511	ret = pthread_cancel(local_apps.ust_listener);
	512	if (ret) {
	513	ERR("Error cancelling local ust listener thread");
	514	}
	515
	516	cleanup_sock_info(&local_apps);
	517
	518	lttng_ust_abi_exit();
	519	ltt_events_exit();
	520	ltt_ring_buffer_client_discard_exit();
	521	ltt_ring_buffer_client_overwrite_exit();
	522	ltt_ring_buffer_metadata_client_exit();
	523	exit_tracepoint();
	524	}