X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=liblttng-ust%2Flttng-ust-comm.c;h=fbdee7d3af8ea0d8d122ab3e4b3bb8a251ccc9a0;hb=549df04044855ca170838fe2f7d92b523445be65;hp=b968b498acc52874b3472544691bbaef05364d48;hpb=cd27263b5ddfee00e67674cae4fdf05b70a43438;p=lttng-ust.git

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index b968b498..fbdee7d3 100644
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -22,7 +22,6 @@
 #define _LGPL_SOURCE
 #include <sys/types.h>
 #include <sys/socket.h>
-#include <sys/prctl.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -42,10 +41,18 @@
 #include <lttng/ust-events.h>
 #include <lttng/ust-abi.h>
 #include <lttng/ust.h>
+#include <lttng/ust-error.h>
+#include <lttng/ust-ctl.h>
+#include <urcu/tls-compat.h>
 #include <ust-comm.h>
 #include <usterr-signal-safe.h>
+#include <helper.h>
 #include "tracepoint-internal.h"
-#include "ltt-tracer-core.h"
+#include "lttng-tracer-core.h"
+#include "compat.h"
+#include "../libringbuffer/tlsfixup.h"
+#include "lttng-ust-baddr.h"
+#include "getenv.h"
 
 /*
  * Has lttng ust comm constructor been called ?
@@ -56,11 +63,140 @@ static int initialized;
  * The ust_lock/ust_unlock lock is used as a communication thread mutex.
  * Held when handling a command, also held by fork() to deal with
  * removal of threads, and by exit path.
+ *
+ * The UST lock is the centralized mutex across UST tracing control and
+ * probe registration.
+ *
+ * ust_exit_mutex must never nest in ust_mutex.
+ *
+ * ust_fork_mutex must never nest in ust_mutex.
+ *
+ * ust_mutex_nest is a per-thread nesting counter, allowing the perf
+ * counter lazy initialization called by events within the statedump,
+ * which traces while the ust_mutex is held.
+ *
+ * ust_lock nests within the dynamic loader lock (within glibc) because
+ * it is taken within the library constructor.
  */
+static pthread_mutex_t ust_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+/* Allow nesting the ust_mutex within the same thread. */
+static DEFINE_URCU_TLS(int, ust_mutex_nest);
+
+/*
+ * ust_exit_mutex protects thread_active variable wrt thread exit. It
+ * cannot be done by ust_mutex because pthread_cancel(), which takes an
+ * internal libc lock, cannot nest within ust_mutex.
+ *
+ * It never nests within a ust_mutex.
+ */
+static pthread_mutex_t ust_exit_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+/*
+ * ust_fork_mutex protects base address statedump tracing against forks. It
+ * prevents the dynamic loader lock to be taken (by base address statedump
+ * tracing) while a fork is happening, thus preventing deadlock issues with
+ * the dynamic loader lock.
+ */
+static pthread_mutex_t ust_fork_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 /* Should the ust comm thread quit ? */
 static int lttng_ust_comm_should_quit;
 
+/*
+ * Return 0 on success, -1 if should quit.
+ * The lock is taken in both cases.
+ * Signal-safe.
+ */
+int ust_lock(void)
+{
+	sigset_t sig_all_blocked, orig_mask;
+	int ret, oldstate;
+
+	ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
+	if (ret) {
+		ERR("pthread_setcancelstate: %s", strerror(ret));
+	}
+	if (oldstate != PTHREAD_CANCEL_ENABLE) {
+		ERR("pthread_setcancelstate: unexpected oldstate");
+	}
+	sigfillset(&sig_all_blocked);
+	ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
+	if (ret) {
+		ERR("pthread_sigmask: %s", strerror(ret));
+	}
+	if (!URCU_TLS(ust_mutex_nest)++)
+		pthread_mutex_lock(&ust_mutex);
+	ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
+	if (ret) {
+		ERR("pthread_sigmask: %s", strerror(ret));
+	}
+	if (lttng_ust_comm_should_quit) {
+		return -1;
+	} else {
+		return 0;
+	}
+}
+
+/*
+ * ust_lock_nocheck() can be used in constructors/destructors, because
+ * they are already nested within the dynamic loader lock, and therefore
+ * have exclusive access against execution of liblttng-ust destructor.
+ * Signal-safe.
+ */
+void ust_lock_nocheck(void)
+{
+	sigset_t sig_all_blocked, orig_mask;
+	int ret, oldstate;
+
+	ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate);
+	if (ret) {
+		ERR("pthread_setcancelstate: %s", strerror(ret));
+	}
+	if (oldstate != PTHREAD_CANCEL_ENABLE) {
+		ERR("pthread_setcancelstate: unexpected oldstate");
+	}
+	sigfillset(&sig_all_blocked);
+	ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
+	if (ret) {
+		ERR("pthread_sigmask: %s", strerror(ret));
+	}
+	if (!URCU_TLS(ust_mutex_nest)++)
+		pthread_mutex_lock(&ust_mutex);
+	ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
+	if (ret) {
+		ERR("pthread_sigmask: %s", strerror(ret));
+	}
+}
+
+/*
+ * Signal-safe.
+ */
+void ust_unlock(void)
+{
+	sigset_t sig_all_blocked, orig_mask;
+	int ret, oldstate;
+
+	sigfillset(&sig_all_blocked);
+	ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask);
+	if (ret) {
+		ERR("pthread_sigmask: %s", strerror(ret));
+	}
+	if (!--URCU_TLS(ust_mutex_nest))
+		pthread_mutex_unlock(&ust_mutex);
+	ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL);
+	if (ret) {
+		ERR("pthread_sigmask: %s", strerror(ret));
+	}
+	ret = pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &oldstate);
+	if (ret) {
+		ERR("pthread_setcancelstate: %s", strerror(ret));
+	}
+	if (oldstate != PTHREAD_CANCEL_DISABLE) {
+		ERR("pthread_setcancelstate: unexpected oldstate");
+	}
+}
+
 /*
  * Wait for either of these before continuing to the main
  * program:
@@ -77,6 +213,12 @@ static sem_t constructor_wait;
  */
 static int sem_count = { 2 };
 
+/*
+ * Counting nesting within lttng-ust. Used to ensure that calling fork()
+ * from liblttng-ust does not execute the pre/post fork handlers.
+ */
+static DEFINE_URCU_TLS(int, lttng_ust_nest_count);
+
 /*
  * Info about socket and associated listener thread.
  */
@@ -87,12 +229,16 @@ struct sock_info {
 	int constructor_sem_posted;
 	int allowed;
 	int global;
+	int thread_active;
 
 	char sock_path[PATH_MAX];
 	int socket;
+	int notify_socket;
 
 	char wait_shm_path[PATH_MAX];
 	char *wait_shm_mmap;
+	/* Keep track of lazy state dump not performed yet. */
+	int statedump_pending;
 };
 
 /* Socket from app (connect) to session daemon (listen) for communication */
@@ -102,11 +248,15 @@ struct sock_info global_apps = {
 
 	.root_handle = -1,
 	.allowed = 1,
+	.thread_active = 0,
 
-	.sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK,
+	.sock_path = LTTNG_DEFAULT_RUNDIR "/" LTTNG_UST_SOCK_FILENAME,
 	.socket = -1,
+	.notify_socket = -1,
 
-	.wait_shm_path = DEFAULT_GLOBAL_APPS_WAIT_SHM_PATH,
+	.wait_shm_path = "/" LTTNG_UST_WAIT_FILENAME,
+
+	.statedump_pending = 0,
 };
 
 /* TODO: allow global_apps_sock_path override */
@@ -116,18 +266,127 @@ struct sock_info local_apps = {
 	.global = 0,
 	.root_handle = -1,
 	.allowed = 0,	/* Check setuid bit first */
+	.thread_active = 0,
 
 	.socket = -1,
+	.notify_socket = -1,
+
+	.statedump_pending = 0,
 };
 
 static int wait_poll_fallback;
 
-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 const char *cmd_name_mapping[] = {
+	[ LTTNG_UST_RELEASE ] = "Release",
+	[ LTTNG_UST_SESSION ] = "Create Session",
+	[ LTTNG_UST_TRACER_VERSION ] = "Get Tracer Version",
+
+	[ LTTNG_UST_TRACEPOINT_LIST ] = "Create Tracepoint List",
+	[ LTTNG_UST_WAIT_QUIESCENT ] = "Wait for Quiescent State",
+	[ LTTNG_UST_REGISTER_DONE ] = "Registration Done",
+	[ LTTNG_UST_TRACEPOINT_FIELD_LIST ] = "Create Tracepoint Field List",
+
+	/* Session FD commands */
+	[ LTTNG_UST_CHANNEL ] = "Create Channel",
+	[ LTTNG_UST_SESSION_START ] = "Start Session",
+	[ LTTNG_UST_SESSION_STOP ] = "Stop Session",
+
+	/* Channel FD commands */
+	[ LTTNG_UST_STREAM ] = "Create Stream",
+	[ LTTNG_UST_EVENT ] = "Create Event",
+
+	/* Event and Channel FD commands */
+	[ LTTNG_UST_CONTEXT ] = "Create Context",
+	[ LTTNG_UST_FLUSH_BUFFER ] = "Flush Buffer",
+
+	/* Event, Channel and Session commands */
+	[ LTTNG_UST_ENABLE ] = "Enable",
+	[ LTTNG_UST_DISABLE ] = "Disable",
+
+	/* Tracepoint list commands */
+	[ LTTNG_UST_TRACEPOINT_LIST_GET ] = "List Next Tracepoint",
+	[ LTTNG_UST_TRACEPOINT_FIELD_LIST_GET ] = "List Next Tracepoint Field",
+
+	/* Event FD commands */
+	[ LTTNG_UST_FILTER ] = "Create Filter",
+	[ LTTNG_UST_EXCLUSION ] = "Add exclusions to event",
+};
+
+static const char *str_timeout;
+static int got_timeout_env;
+
+extern void lttng_ring_buffer_client_overwrite_init(void);
+extern void lttng_ring_buffer_client_overwrite_rt_init(void);
+extern void lttng_ring_buffer_client_discard_init(void);
+extern void lttng_ring_buffer_client_discard_rt_init(void);
+extern void lttng_ring_buffer_metadata_client_init(void);
+extern void lttng_ring_buffer_client_overwrite_exit(void);
+extern void lttng_ring_buffer_client_overwrite_rt_exit(void);
+extern void lttng_ring_buffer_client_discard_exit(void);
+extern void lttng_ring_buffer_client_discard_rt_exit(void);
+extern void lttng_ring_buffer_metadata_client_exit(void);
+
+/*
+ * Returns the HOME directory path. Caller MUST NOT free(3) the returned
+ * pointer.
+ */
+static
+const char *get_lttng_home_dir(void)
+{
+       const char *val;
+
+       val = (const char *) lttng_secure_getenv("LTTNG_HOME");
+       if (val != NULL) {
+               return val;
+       }
+       return (const char *) lttng_secure_getenv("HOME");
+}
+
+/*
+ * Force a read (imply TLS fixup for dlopen) of TLS variables.
+ */
+static
+void lttng_fixup_nest_count_tls(void)
+{
+	asm volatile ("" : : "m" (URCU_TLS(lttng_ust_nest_count)));
+}
+
+static
+void lttng_fixup_ust_mutex_nest_tls(void)
+{
+	asm volatile ("" : : "m" (URCU_TLS(ust_mutex_nest)));
+}
+
+/*
+ * Fixup urcu bp TLS.
+ */
+static
+void lttng_fixup_urcu_bp_tls(void)
+{
+	rcu_read_lock();
+	rcu_read_unlock();
+}
+
+int lttng_get_notify_socket(void *owner)
+{
+	struct sock_info *info = owner;
+
+	return info->notify_socket;
+}
+
+static
+void print_cmd(int cmd, int handle)
+{
+	const char *cmd_name = "Unknown";
+
+	if (cmd >= 0 && cmd < LTTNG_ARRAY_SIZE(cmd_name_mapping)
+			&& cmd_name_mapping[cmd]) {
+		cmd_name = cmd_name_mapping[cmd];
+	}
+	DBG("Message Received \"%s\" (%d), Handle \"%s\" (%d)",
+		cmd_name, cmd,
+		lttng_ust_obj_get_name(handle), handle);
+}
 
 static
 int setup_local_apps(void)
@@ -140,54 +399,99 @@ int setup_local_apps(void)
 	 * Disallow per-user tracing for setuid binaries.
 	 */
 	if (uid != geteuid()) {
-		local_apps.allowed = 0;
+		assert(local_apps.allowed == 0);
 		return 0;
-	} else {
-		local_apps.allowed = 1;
 	}
-	home_dir = (const char *) getenv("HOME");
-	if (!home_dir)
+	home_dir = get_lttng_home_dir();
+	if (!home_dir) {
+		WARN("HOME environment variable not set. Disabling LTTng-UST per-user tracing.");
+		assert(local_apps.allowed == 0);
 		return -ENOENT;
-	snprintf(local_apps.sock_path, PATH_MAX,
-		 DEFAULT_HOME_APPS_UNIX_SOCK, home_dir);
-	snprintf(local_apps.wait_shm_path, PATH_MAX,
-		 DEFAULT_HOME_APPS_WAIT_SHM_PATH, uid);
+	}
+	local_apps.allowed = 1;
+	snprintf(local_apps.sock_path, PATH_MAX, "%s/%s/%s",
+		home_dir,
+		LTTNG_DEFAULT_HOME_RUNDIR,
+		LTTNG_UST_SOCK_FILENAME);
+	snprintf(local_apps.wait_shm_path, PATH_MAX, "/%s-%u",
+		LTTNG_UST_WAIT_FILENAME,
+		uid);
 	return 0;
 }
 
+/*
+ * Get notify_sock timeout, in ms.
+ * -1: wait forever. 0: don't wait. >0: timeout, in ms.
+ */
 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;
-		uint32_t bits_per_long;
-		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();
-	reg_msg.bits_per_long = CAA_BITS_PER_LONG;
-	prctl_ret = prctl(PR_GET_NAME, (unsigned long) reg_msg.name, 0, 0, 0);
-	if (prctl_ret) {
-		ERR("Error executing prctl");
-		return -errno;
-	}
-
-	ret = ustcomm_send_unix_sock(socket, &reg_msg, sizeof(reg_msg));
-	if (ret >= 0 && ret != sizeof(reg_msg))
-		return -EIO;
-	return ret;
+long get_timeout(void)
+{
+	long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
+
+	if (!got_timeout_env) {
+		str_timeout = getenv("LTTNG_UST_REGISTER_TIMEOUT");
+		got_timeout_env = 1;
+	}
+	if (str_timeout)
+		constructor_delay_ms = strtol(str_timeout, NULL, 10);
+	return constructor_delay_ms;
+}
+
+static
+long get_notify_sock_timeout(void)
+{
+	return get_timeout();
+}
+
+/*
+ * Return values: -1: wait forever. 0: don't wait. 1: timeout wait.
+ */
+static
+int get_constructor_timeout(struct timespec *constructor_timeout)
+{
+	long constructor_delay_ms;
+	int ret;
+
+	constructor_delay_ms = get_timeout();
+
+	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) {
+		/* Don't wait. */
+		return 0;
+	}
+	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;
+	}
+	/* Timeout wait (constructor_delay_ms). */
+	return 1;
+}
+
+static
+int register_to_sessiond(int socket, enum ustctl_socket_type type)
+{
+	return ustcomm_send_reg_msg(socket,
+		type,
+		CAA_BITS_PER_LONG,
+		lttng_alignof(uint8_t) * CHAR_BIT,
+		lttng_alignof(uint16_t) * CHAR_BIT,
+		lttng_alignof(uint32_t) * CHAR_BIT,
+		lttng_alignof(uint64_t) * CHAR_BIT,
+		lttng_alignof(unsigned long) * CHAR_BIT);
 }
 
 static
@@ -200,15 +504,15 @@ int send_reply(int sock, struct ustcomm_ust_reply *lur)
 	case sizeof(*lur):
 		DBG("message successfully sent");
 		return 0;
-	case -1:
-		if (errno == ECONNRESET) {
-			printf("remote end closed connection\n");
+	default:
+		if (len == -ECONNRESET) {
+			DBG("remote end closed connection");
 			return 0;
 		}
-		return -1;
-	default:
-		printf("incorrect message size: %zd\n", len);
-		return -1;
+		if (len < 0)
+			return len;
+		DBG("incorrect message size: %zd", len);
+		return -EINVAL;
 	}
 }
 
@@ -231,6 +535,30 @@ int handle_register_done(struct sock_info *sock_info)
 	return 0;
 }
 
+/*
+ * Only execute pending statedump after the constructor semaphore has
+ * been posted by each listener thread. This means statedump will only
+ * be performed after the "registration done" command is received from
+ * each session daemon the application is connected to.
+ *
+ * This ensures we don't run into deadlock issues with the dynamic
+ * loader mutex, which is held while the constructor is called and
+ * waiting on the constructor semaphore. All operations requiring this
+ * dynamic loader lock need to be postponed using this mechanism.
+ */
+static
+void handle_pending_statedump(struct sock_info *sock_info)
+{
+	int ctor_passed = sock_info->constructor_sem_posted;
+
+	if (ctor_passed && sock_info->statedump_pending) {
+		sock_info->statedump_pending = 0;
+		pthread_mutex_lock(&ust_fork_mutex);
+		lttng_handle_pending_statedump(sock_info);
+		pthread_mutex_unlock(&ust_fork_mutex);
+	}
+}
+
 static
 int handle_message(struct sock_info *sock_info,
 		int sock, struct ustcomm_ust_msg *lum)
@@ -238,21 +566,20 @@ int handle_message(struct sock_info *sock_info,
 	int ret = 0;
 	const struct lttng_ust_objd_ops *ops;
 	struct ustcomm_ust_reply lur;
-	int shm_fd, wait_fd;
-
-	ust_lock();
+	union ust_args args;
+	ssize_t len;
 
 	memset(&lur, 0, sizeof(lur));
 
-	if (lttng_ust_comm_should_quit) {
-		ret = -EPERM;
-		goto end;
+	if (ust_lock()) {
+		ret = -LTTNG_UST_ERR_EXITING;
+		goto error;
 	}
 
 	ops = objd_ops(lum->handle);
 	if (!ops) {
 		ret = -ENOENT;
-		goto end;
+		goto error;
 	}
 
 	switch (lum->cmd) {
@@ -266,105 +593,345 @@ int handle_message(struct sock_info *sock_info,
 		if (lum->handle == LTTNG_UST_ROOT_HANDLE)
 			ret = -EPERM;
 		else
-			ret = lttng_ust_objd_unref(lum->handle);
+			ret = lttng_ust_objd_unref(lum->handle, 1);
+		break;
+	case LTTNG_UST_FILTER:
+	{
+		/* Receive filter data */
+		struct lttng_ust_filter_bytecode_node *bytecode;
+
+		if (lum->u.filter.data_size > FILTER_BYTECODE_MAX_LEN) {
+			ERR("Filter data size is too large: %u bytes",
+				lum->u.filter.data_size);
+			ret = -EINVAL;
+			goto error;
+		}
+
+		if (lum->u.filter.reloc_offset > lum->u.filter.data_size) {
+			ERR("Filter reloc offset %u is not within data",
+				lum->u.filter.reloc_offset);
+			ret = -EINVAL;
+			goto error;
+		}
+
+		bytecode = zmalloc(sizeof(*bytecode) + lum->u.filter.data_size);
+		if (!bytecode) {
+			ret = -ENOMEM;
+			goto error;
+		}
+		len = ustcomm_recv_unix_sock(sock, bytecode->bc.data,
+				lum->u.filter.data_size);
+		switch (len) {
+		case 0:	/* orderly shutdown */
+			ret = 0;
+			free(bytecode);
+			goto error;
+		default:
+			if (len == lum->u.filter.data_size) {
+				DBG("filter data received");
+				break;
+			} else if (len < 0) {
+				DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
+				if (len == -ECONNRESET) {
+					ERR("%s remote end closed connection", sock_info->name);
+					ret = len;
+					free(bytecode);
+					goto error;
+				}
+				ret = len;
+				free(bytecode);
+				goto error;
+			} else {
+				DBG("incorrect filter data message size: %zd", len);
+				ret = -EINVAL;
+				free(bytecode);
+				goto error;
+			}
+		}
+		bytecode->bc.len = lum->u.filter.data_size;
+		bytecode->bc.reloc_offset = lum->u.filter.reloc_offset;
+		bytecode->bc.seqnum = lum->u.filter.seqnum;
+		if (ops->cmd) {
+			ret = ops->cmd(lum->handle, lum->cmd,
+					(unsigned long) bytecode,
+					&args, sock_info);
+			if (ret) {
+				free(bytecode);
+			}
+			/* don't free bytecode if everything went fine. */
+		} else {
+			ret = -ENOSYS;
+			free(bytecode);
+		}
+		break;
+	}
+	case LTTNG_UST_EXCLUSION:
+	{
+		/* Receive exclusion names */
+		struct lttng_ust_excluder_node *node;
+		unsigned int count;
+
+		count = lum->u.exclusion.count;
+		if (count == 0) {
+			/* There are no names to read */
+			ret = 0;
+			goto error;
+		}
+		node = zmalloc(sizeof(*node) +
+				count * LTTNG_UST_SYM_NAME_LEN);
+		if (!node) {
+			ret = -ENOMEM;
+			goto error;
+		}
+		node->excluder.count = count;
+		len = ustcomm_recv_unix_sock(sock, node->excluder.names,
+				count * LTTNG_UST_SYM_NAME_LEN);
+		switch (len) {
+		case 0:	/* orderly shutdown */
+			ret = 0;
+			free(node);
+			goto error;
+		default:
+			if (len == count * LTTNG_UST_SYM_NAME_LEN) {
+				DBG("Exclusion data received");
+				break;
+			} else if (len < 0) {
+				DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
+				if (len == -ECONNRESET) {
+					ERR("%s remote end closed connection", sock_info->name);
+					ret = len;
+					free(node);
+					goto error;
+				}
+				ret = len;
+				free(node);
+				goto error;
+			} else {
+				DBG("Incorrect exclusion data message size: %zd", len);
+				ret = -EINVAL;
+				free(node);
+				goto error;
+			}
+		}
+		if (ops->cmd) {
+			ret = ops->cmd(lum->handle, lum->cmd,
+					(unsigned long) node,
+					&args, sock_info);
+			if (ret) {
+				free(node);
+			}
+			/* Don't free exclusion data if everything went fine. */
+		} else {
+			ret = -ENOSYS;
+			free(node);
+		}
+		break;
+	}
+	case LTTNG_UST_CHANNEL:
+	{
+		void *chan_data;
+		int wakeup_fd;
+
+		len = ustcomm_recv_channel_from_sessiond(sock,
+				&chan_data, lum->u.channel.len,
+				&wakeup_fd);
+		switch (len) {
+		case 0:	/* orderly shutdown */
+			ret = 0;
+			goto error;
+		default:
+			if (len == lum->u.channel.len) {
+				DBG("channel data received");
+				break;
+			} else if (len < 0) {
+				DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
+				if (len == -ECONNRESET) {
+					ERR("%s remote end closed connection", sock_info->name);
+					ret = len;
+					goto error;
+				}
+				ret = len;
+				goto error;
+			} else {
+				DBG("incorrect channel data message size: %zd", len);
+				ret = -EINVAL;
+				goto error;
+			}
+		}
+		args.channel.chan_data = chan_data;
+		args.channel.wakeup_fd = wakeup_fd;
+		if (ops->cmd)
+			ret = ops->cmd(lum->handle, lum->cmd,
+					(unsigned long) &lum->u,
+					&args, sock_info);
+		else
+			ret = -ENOSYS;
 		break;
+	}
+	case LTTNG_UST_STREAM:
+	{
+		/* Receive shm_fd, wakeup_fd */
+		ret = ustcomm_recv_stream_from_sessiond(sock,
+			&lum->u.stream.len,
+			&args.stream.shm_fd,
+			&args.stream.wakeup_fd);
+		if (ret) {
+			goto error;
+		}
+		if (ops->cmd)
+			ret = ops->cmd(lum->handle, lum->cmd,
+					(unsigned long) &lum->u,
+					&args, sock_info);
+		else
+			ret = -ENOSYS;
+		break;
+	}
 	default:
 		if (ops->cmd)
 			ret = ops->cmd(lum->handle, lum->cmd,
-					(unsigned long) &lum->u);
+					(unsigned long) &lum->u,
+					&args, sock_info);
 		else
 			ret = -ENOSYS;
 		break;
 	}
 
-end:
 	lur.handle = lum->handle;
 	lur.cmd = lum->cmd;
 	lur.ret_val = ret;
 	if (ret >= 0) {
-		lur.ret_code = USTCOMM_OK;
+		lur.ret_code = LTTNG_UST_OK;
 	} else {
-		//lur.ret_code = USTCOMM_SESSION_FAIL;
-		lur.ret_code = ret;
-	}
-	switch (lum->cmd) {
-	case LTTNG_UST_STREAM:
 		/*
-		 * Special-case reply to send stream info.
-		 * Use lum.u output.
+		 * Use -LTTNG_UST_ERR as wildcard for UST internal
+		 * error that are not caused by the transport, except if
+		 * we already have a more precise error message to
+		 * report.
 		 */
-		lur.u.stream.memory_map_size = lum->u.stream.memory_map_size;
-		shm_fd = lum->u.stream.shm_fd;
-		wait_fd = lum->u.stream.wait_fd;
-		break;
-	case LTTNG_UST_METADATA:
-	case LTTNG_UST_CHANNEL:
-		lur.u.channel.memory_map_size = lum->u.channel.memory_map_size;
-		shm_fd = lum->u.channel.shm_fd;
-		wait_fd = lum->u.channel.wait_fd;
-		break;
-	case LTTNG_UST_TRACER_VERSION:
-		lur.u.version = lum->u.version;
-		break;
-	case LTTNG_UST_TRACEPOINT_LIST_GET:
-		memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
-		break;
+		if (ret > -LTTNG_UST_ERR) {
+			/* Translate code to UST error. */
+			switch (ret) {
+			case -EEXIST:
+				lur.ret_code = -LTTNG_UST_ERR_EXIST;
+				break;
+			case -EINVAL:
+				lur.ret_code = -LTTNG_UST_ERR_INVAL;
+				break;
+			case -ENOENT:
+				lur.ret_code = -LTTNG_UST_ERR_NOENT;
+				break;
+			case -EPERM:
+				lur.ret_code = -LTTNG_UST_ERR_PERM;
+				break;
+			case -ENOSYS:
+				lur.ret_code = -LTTNG_UST_ERR_NOSYS;
+				break;
+			default:
+				lur.ret_code = -LTTNG_UST_ERR;
+				break;
+			}
+		} else {
+			lur.ret_code = ret;
+		}
+	}
+	if (ret >= 0) {
+		switch (lum->cmd) {
+		case LTTNG_UST_TRACER_VERSION:
+			lur.u.version = lum->u.version;
+			break;
+		case LTTNG_UST_TRACEPOINT_LIST_GET:
+			memcpy(&lur.u.tracepoint, &lum->u.tracepoint, sizeof(lur.u.tracepoint));
+			break;
+		}
 	}
+	DBG("Return value: %d", lur.ret_val);
 	ret = send_reply(sock, &lur);
 	if (ret < 0) {
-		perror("error sending reply");
+		DBG("error sending reply");
 		goto error;
 	}
 
-	if ((lum->cmd == LTTNG_UST_STREAM
-	     || lum->cmd == LTTNG_UST_CHANNEL
-	     || lum->cmd == LTTNG_UST_METADATA)
-			&& lur.ret_code == USTCOMM_OK) {
-		/* we also need to send the file descriptors. */
-		ret = ustcomm_send_fds_unix_sock(sock,
-			&shm_fd, &shm_fd,
-			1, sizeof(int));
-		if (ret < 0) {
-			perror("send shm_fd");
-			goto error;
-		}
-		ret = ustcomm_send_fds_unix_sock(sock,
-			&wait_fd, &wait_fd,
-			1, sizeof(int));
-		if (ret < 0) {
-			perror("send wait_fd");
-			goto error;
+	/*
+	 * LTTNG_UST_TRACEPOINT_FIELD_LIST_GET needs to send the field
+	 * after the reply.
+	 */
+	if (lur.ret_code == LTTNG_UST_OK) {
+		switch (lum->cmd) {
+		case LTTNG_UST_TRACEPOINT_FIELD_LIST_GET:
+			len = ustcomm_send_unix_sock(sock,
+				&args.field_list.entry,
+				sizeof(args.field_list.entry));
+			if (len < 0) {
+				ret = len;
+				goto error;
+			}
+			if (len != sizeof(args.field_list.entry)) {
+				ret = -EINVAL;
+				goto error;
+			}
 		}
 	}
+
 error:
 	ust_unlock();
+
+	/*
+	 * Performed delayed statedump operations outside of the UST
+	 * lock. We need to take the dynamic loader lock before we take
+	 * the UST lock internally within handle_pending_statedump().
+	  */
+	handle_pending_statedump(sock_info);
+
 	return ret;
 }
 
 static
-void cleanup_sock_info(struct sock_info *sock_info)
+void cleanup_sock_info(struct sock_info *sock_info, int exiting)
 {
 	int ret;
 
+	if (sock_info->root_handle != -1) {
+		ret = lttng_ust_objd_unref(sock_info->root_handle, 1);
+		if (ret) {
+			ERR("Error unref root handle");
+		}
+		sock_info->root_handle = -1;
+	}
+	sock_info->constructor_sem_posted = 0;
+
+	/*
+	 * wait_shm_mmap, socket and notify socket are used by listener
+	 * threads outside of the ust lock, so we cannot tear them down
+	 * ourselves, because we cannot join on these threads. Leave
+	 * responsibility of cleaning up these resources to the OS
+	 * process exit.
+	 */
+	if (exiting)
+		return;
+
 	if (sock_info->socket != -1) {
-		ret = close(sock_info->socket);
+		ret = ustcomm_close_unix_sock(sock_info->socket);
 		if (ret) {
-			ERR("Error closing apps socket");
+			ERR("Error closing ust cmd socket");
 		}
 		sock_info->socket = -1;
 	}
-	if (sock_info->root_handle != -1) {
-		ret = lttng_ust_objd_unref(sock_info->root_handle);
+	if (sock_info->notify_socket != -1) {
+		ret = ustcomm_close_unix_sock(sock_info->notify_socket);
 		if (ret) {
-			ERR("Error unref root handle");
+			ERR("Error closing ust notify socket");
 		}
-		sock_info->root_handle = -1;
+		sock_info->notify_socket = -1;
 	}
-	sock_info->constructor_sem_posted = 0;
 	if (sock_info->wait_shm_mmap) {
-		ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE));
-		if (ret) {
-			ERR("Error unmapping wait shm");
+		long page_size;
+
+		page_size = sysconf(_SC_PAGE_SIZE);
+		if (page_size > 0) {
+			ret = munmap(sock_info->wait_shm_mmap, page_size);
+			if (ret) {
+				ERR("Error unmapping wait shm");
+			}
 		}
 		sock_info->wait_shm_mmap = NULL;
 	}
@@ -390,6 +957,30 @@ int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 	 */
 	wait_shm_fd = shm_open(sock_info->wait_shm_path, O_RDONLY, 0);
 	if (wait_shm_fd >= 0) {
+		int32_t tmp_read;
+		ssize_t len;
+		size_t bytes_read = 0;
+
+		/*
+		 * Try to read the fd. If unable to do so, try opening
+		 * it in write mode.
+		 */
+		do {
+			len = read(wait_shm_fd,
+				&((char *) &tmp_read)[bytes_read],
+				sizeof(tmp_read) - bytes_read);
+			if (len > 0) {
+				bytes_read += len;
+			}
+		} while ((len < 0 && errno == EINTR)
+			|| (len > 0 && bytes_read < sizeof(tmp_read)));
+		if (bytes_read != sizeof(tmp_read)) {
+			ret = close(wait_shm_fd);
+			if (ret) {
+				ERR("close wait_shm_fd");
+			}
+			goto open_write;
+		}
 		goto end;
 	} else if (wait_shm_fd < 0 && errno != ENOENT) {
 		/*
@@ -400,11 +991,15 @@ int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 		ERR("Error opening shm %s", sock_info->wait_shm_path);
 		goto end;
 	}
+
+open_write:
 	/*
-	 * If the open failed because the file did not exist, try
-	 * creating it ourself.
+	 * If the open failed because the file did not exist, or because
+	 * the file was not truncated yet, try creating it ourself.
 	 */
+	URCU_TLS(lttng_ust_nest_count)++;
 	pid = fork();
+	URCU_TLS(lttng_ust_nest_count)--;
 	if (pid > 0) {
 		int status;
 
@@ -453,9 +1048,9 @@ int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 			ret = ftruncate(wait_shm_fd, mmap_size);
 			if (ret) {
 				PERROR("ftruncate");
-				exit(EXIT_FAILURE);
+				_exit(EXIT_FAILURE);
 			}
-			exit(EXIT_SUCCESS);
+			_exit(EXIT_SUCCESS);
 		}
 		/*
 		 * For local shm, we need to have rw access to accept
@@ -467,13 +1062,13 @@ int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 		 */
 		if (!sock_info->global && errno != EACCES) {
 			ERR("Error opening shm %s", sock_info->wait_shm_path);
-			exit(EXIT_FAILURE);
+			_exit(EXIT_FAILURE);
 		}
 		/*
 		 * The shm exists, but we cannot open it RW. Report
 		 * success.
 		 */
-		exit(EXIT_SUCCESS);
+		_exit(EXIT_SUCCESS);
 	} else {
 		return -1;
 	}
@@ -509,15 +1104,20 @@ error_close:
 static
 char *get_map_shm(struct sock_info *sock_info)
 {
-	size_t mmap_size = sysconf(_SC_PAGE_SIZE);
+	long page_size;
 	int wait_shm_fd, ret;
 	char *wait_shm_mmap;
 
-	wait_shm_fd = get_wait_shm(sock_info, mmap_size);
+	page_size = sysconf(_SC_PAGE_SIZE);
+	if (page_size < 0) {
+		goto error;
+	}
+
+	wait_shm_fd = get_wait_shm(sock_info, page_size);
 	if (wait_shm_fd < 0) {
 		goto error;
 	}
-	wait_shm_mmap = mmap(NULL, mmap_size, PROT_READ,
+	wait_shm_mmap = mmap(NULL, page_size, PROT_READ,
 		  MAP_SHARED, wait_shm_fd, 0);
 	/* close shm fd immediately after taking the mmap reference */
 	ret = close(wait_shm_fd);
@@ -537,10 +1137,7 @@ error:
 static
 void wait_for_sessiond(struct sock_info *sock_info)
 {
-	int ret;
-
-	ust_lock();
-	if (lttng_ust_comm_should_quit) {
+	if (ust_lock()) {
 		goto quit;
 	}
 	if (wait_poll_fallback) {
@@ -555,23 +1152,32 @@ void wait_for_sessiond(struct sock_info *sock_info)
 
 	DBG("Waiting for %s apps sessiond", sock_info->name);
 	/* Wait for futex wakeup */
-	if (uatomic_read((int32_t *) sock_info->wait_shm_mmap) == 0) {
-		ret = futex_async((int32_t *) sock_info->wait_shm_mmap,
-			FUTEX_WAIT, 0, NULL, NULL, 0);
-		if (ret < 0) {
-			if (errno == EFAULT) {
-				wait_poll_fallback = 1;
-				DBG(
+	if (uatomic_read((int32_t *) sock_info->wait_shm_mmap))
+		goto end_wait;
+
+	while (futex_async((int32_t *) sock_info->wait_shm_mmap,
+			FUTEX_WAIT, 0, NULL, NULL, 0)) {
+		switch (errno) {
+		case EWOULDBLOCK:
+			/* Value already changed. */
+			goto end_wait;
+		case EINTR:
+			/* Retry if interrupted by signal. */
+			break;	/* Get out of switch. */
+		case EFAULT:
+			wait_poll_fallback = 1;
+			DBG(
 "Linux kernels 2.6.33 to 3.0 (with the exception of stable versions) "
 "do not support FUTEX_WAKE on read-only memory mappings correctly. "
 "Please upgrade your kernel "
 "(fix is commit 9ea71503a8ed9184d2d0b8ccc4d269d05f7940ae in Linux kernel "
 "mainline). LTTng-UST will use polling mode fallback.");
-				if (ust_debug())
-					PERROR("futex");
-			}
+			if (ust_debug())
+				PERROR("futex");
+			goto end_wait;
 		}
 	}
+end_wait:
 	return;
 
 quit:
@@ -587,7 +1193,7 @@ error:
  * 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
+ * The other moment it allocates resources is at socket connection, which
  * is also protected by the mutex.
  */
 static
@@ -595,6 +1201,7 @@ void *ust_listener_thread(void *arg)
 {
 	struct sock_info *sock_info = arg;
 	int sock, ret, prev_connect_failed = 0, has_waited = 0;
+	long timeout;
 
 	/* Restart trying to connect to the session daemon */
 restart:
@@ -613,26 +1220,41 @@ restart:
 		has_waited = 1;
 		prev_connect_failed = 0;
 	}
-	ust_lock();
-
-	if (lttng_ust_comm_should_quit) {
-		ust_unlock();
-		goto quit;
-	}
 
 	if (sock_info->socket != -1) {
-		ret = close(sock_info->socket);
+		ret = ustcomm_close_unix_sock(sock_info->socket);
 		if (ret) {
-			ERR("Error closing %s apps socket", sock_info->name);
+			ERR("Error closing %s ust cmd socket",
+				sock_info->name);
 		}
 		sock_info->socket = -1;
 	}
+	if (sock_info->notify_socket != -1) {
+		ret = ustcomm_close_unix_sock(sock_info->notify_socket);
+		if (ret) {
+			ERR("Error closing %s ust notify socket",
+				sock_info->name);
+		}
+		sock_info->notify_socket = -1;
+	}
 
-	/* Register */
+	/*
+	 * Register. We need to perform both connect and sending
+	 * registration message before doing the next connect otherwise
+	 * we may reach unix socket connect queue max limits and block
+	 * on the 2nd connect while the session daemon is awaiting the
+	 * first connect registration message.
+	 */
+	/* Connect cmd socket */
 	ret = ustcomm_connect_unix_sock(sock_info->sock_path);
 	if (ret < 0) {
 		DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
 		prev_connect_failed = 1;
+
+		if (ust_lock()) {
+			goto quit;
+		}
+
 		/*
 		 * If we cannot find the sessiond daemon, don't delay
 		 * constructor execution.
@@ -642,26 +1264,95 @@ restart:
 		ust_unlock();
 		goto restart;
 	}
+	sock_info->socket = ret;
 
-	sock_info->socket = sock = ret;
+	if (ust_lock()) {
+		goto quit;
+	}
 
 	/*
 	 * Create only one root handle per listener thread for the whole
-	 * process lifetime.
+	 * process lifetime, so we ensure we get ID which is statically
+	 * assigned to the root handle.
 	 */
 	if (sock_info->root_handle == -1) {
 		ret = lttng_abi_create_root_handle();
 		if (ret < 0) {
 			ERR("Error creating root handle");
-			ust_unlock();
 			goto quit;
 		}
 		sock_info->root_handle = ret;
 	}
 
-	ret = register_app_to_sessiond(sock);
+	ret = register_to_sessiond(sock_info->socket, USTCTL_SOCKET_CMD);
+	if (ret < 0) {
+		ERR("Error registering to %s ust cmd socket",
+			sock_info->name);
+		prev_connect_failed = 1;
+		/*
+		 * If we cannot register to the sessiond daemon, don't
+		 * delay constructor execution.
+		 */
+		ret = handle_register_done(sock_info);
+		assert(!ret);
+		ust_unlock();
+		goto restart;
+	}
+
+	ust_unlock();
+
+	/* Connect notify socket */
+	ret = ustcomm_connect_unix_sock(sock_info->sock_path);
+	if (ret < 0) {
+		DBG("Info: sessiond not accepting connections to %s apps socket", sock_info->name);
+		prev_connect_failed = 1;
+
+		if (ust_lock()) {
+			goto quit;
+		}
+
+		/*
+		 * If we cannot find the sessiond daemon, don't delay
+		 * constructor execution.
+		 */
+		ret = handle_register_done(sock_info);
+		assert(!ret);
+		ust_unlock();
+		goto restart;
+	}
+	sock_info->notify_socket = ret;
+
+	timeout = get_notify_sock_timeout();
+	if (timeout >= 0) {
+		/*
+		 * Give at least 10ms to sessiond to reply to
+		 * notifications.
+		 */
+		if (timeout < 10)
+			timeout = 10;
+		ret = ustcomm_setsockopt_rcv_timeout(sock_info->notify_socket,
+				timeout);
+		if (ret < 0) {
+			WARN("Error setting socket receive timeout");
+		}
+		ret = ustcomm_setsockopt_snd_timeout(sock_info->notify_socket,
+				timeout);
+		if (ret < 0) {
+			WARN("Error setting socket send timeout");
+		}
+	} else if (timeout < -1) {
+		WARN("Unsupported timeout value %ld", timeout);
+	}
+
+	if (ust_lock()) {
+		goto quit;
+	}
+
+	ret = register_to_sessiond(sock_info->notify_socket,
+			USTCTL_SOCKET_NOTIFY);
 	if (ret < 0) {
-		ERR("Error registering to %s apps socket", sock_info->name);
+		ERR("Error registering to %s ust notify socket",
+			sock_info->name);
 		prev_connect_failed = 1;
 		/*
 		 * If we cannot register to the sessiond daemon, don't
@@ -672,6 +1363,8 @@ restart:
 		ust_unlock();
 		goto restart;
 	}
+	sock = sock_info->socket;
+
 	ust_unlock();
 
 	for (;;) {
@@ -681,8 +1374,10 @@ restart:
 		len = ustcomm_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);
-			ust_lock();
+			DBG("%s lttng-sessiond has performed an orderly shutdown", sock_info->name);
+			if (ust_lock()) {
+				goto quit;
+			}
 			/*
 			 * Either sessiond has shutdown or refused us by closing the socket.
 			 * In either case, we don't want to delay construction execution,
@@ -698,86 +1393,85 @@ restart:
 			ust_unlock();
 			goto end;
 		case sizeof(lum):
-			DBG("message received\n");
+			print_cmd(lum.cmd, lum.handle);
 			ret = handle_message(sock_info, sock, &lum);
-			if (ret < 0) {
-				ERR("Error handling message for %s socket", sock_info->name);
+			if (ret) {
+				ERR("Error handling message for %s socket",
+					sock_info->name);
+				/*
+				 * Close socket if protocol error is
+				 * detected.
+				 */
+				goto end;
 			}
 			continue;
-		case -1:
-			DBG("Receive failed from lttng-sessiond with errno %d", errno);
-			if (errno == ECONNRESET) {
-				ERR("%s remote end closed connection\n", sock_info->name);
+		default:
+			if (len < 0) {
+				DBG("Receive failed from lttng-sessiond with errno %d", (int) -len);
+			} else {
+				DBG("incorrect message size (%s socket): %zd", sock_info->name, len);
+			}
+			if (len == -ECONNRESET) {
+				DBG("%s remote end closed connection", sock_info->name);
 				goto end;
 			}
 			goto end;
-		default:
-			ERR("incorrect message size (%s socket): %zd\n", sock_info->name, len);
-			continue;
 		}
 
 	}
 end:
+	if (ust_lock()) {
+		goto quit;
+	}
+	/* Cleanup socket handles before trying to reconnect */
+	lttng_ust_objd_table_owner_cleanup(sock_info);
+	ust_unlock();
 	goto restart;	/* try to reconnect */
+
 quit:
+	ust_unlock();
+
+	pthread_mutex_lock(&ust_exit_mutex);
+	sock_info->thread_active = 0;
+	pthread_mutex_unlock(&ust_exit_mutex);
 	return NULL;
 }
 
 /*
- * Return values: -1: don't wait. 0: wait forever. 1: timeout wait.
+ * Weak symbol to call when the ust malloc wrapper is not loaded.
  */
-static
-int get_timeout(struct timespec *constructor_timeout)
+__attribute__((weak))
+void lttng_ust_malloc_wrapper_init(void)
 {
-	long constructor_delay_ms = LTTNG_UST_DEFAULT_CONSTRUCTOR_TIMEOUT_MS;
-	char *str_delay;
-	int ret;
-
-	str_delay = getenv("LTTNG_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;
+	sigset_t sig_all_blocked, orig_parent_mask;
+	pthread_attr_t thread_attr;
 	int timeout_mode;
 	int ret;
 
 	if (uatomic_xchg(&initialized, 1) == 1)
 		return;
 
+	/*
+	 * Fixup interdependency between TLS fixup mutex (which happens
+	 * to be the dynamic linker mutex) and ust_lock, taken within
+	 * the ust lock.
+	 */
+	lttng_fixup_urcu_bp_tls();
+	lttng_fixup_ringbuffer_tls();
+	lttng_fixup_vtid_tls();
+	lttng_fixup_nest_count_tls();
+	lttng_fixup_procname_tls();
+	lttng_fixup_ust_mutex_nest_tls();
+
 	/*
 	 * We want precise control over the order in which we construct
 	 * our sub-libraries vs starting to receive commands from
@@ -786,28 +1480,80 @@ void __attribute__((constructor)) lttng_ust_init(void)
 	 */
 	init_usterr();
 	init_tracepoint();
-	ltt_ring_buffer_metadata_client_init();
-	ltt_ring_buffer_client_overwrite_init();
-	ltt_ring_buffer_client_discard_init();
+	lttng_ust_baddr_statedump_init();
+	lttng_ring_buffer_metadata_client_init();
+	lttng_ring_buffer_client_overwrite_init();
+	lttng_ring_buffer_client_overwrite_rt_init();
+	lttng_ring_buffer_client_discard_init();
+	lttng_ring_buffer_client_discard_rt_init();
+	lttng_perf_counter_init();
+	lttng_context_init();
+	/*
+	 * Invoke ust malloc wrapper init before starting other threads.
+	 */
+	lttng_ust_malloc_wrapper_init();
 
-	timeout_mode = get_timeout(&constructor_timeout);
+	timeout_mode = get_constructor_timeout(&constructor_timeout);
 
 	ret = sem_init(&constructor_wait, 0, 0);
 	assert(!ret);
 
 	ret = setup_local_apps();
 	if (ret) {
-		ERR("Error setting up to local apps");
+		DBG("local apps setup returned %d", ret);
 	}
-	ret = pthread_create(&local_apps.ust_listener, NULL,
-			ust_listener_thread, &local_apps);
+
+	/* A new thread created by pthread_create inherits the signal mask
+	 * from the parent. To avoid any signal being received by the
+	 * listener thread, we block all signals temporarily in the parent,
+	 * while we create the listener thread.
+	 */
+	sigfillset(&sig_all_blocked);
+	ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_parent_mask);
+	if (ret) {
+		ERR("pthread_sigmask: %s", strerror(ret));
+	}
+
+	ret = pthread_attr_init(&thread_attr);
+	if (ret) {
+		ERR("pthread_attr_init: %s", strerror(ret));
+	}
+	ret = pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_DETACHED);
+	if (ret) {
+		ERR("pthread_attr_setdetachstate: %s", strerror(ret));
+	}
+
+	pthread_mutex_lock(&ust_exit_mutex);
+	ret = pthread_create(&global_apps.ust_listener, &thread_attr,
+			ust_listener_thread, &global_apps);
+	if (ret) {
+		ERR("pthread_create global: %s", strerror(ret));
+	}
+	global_apps.thread_active = 1;
+	pthread_mutex_unlock(&ust_exit_mutex);
 
 	if (local_apps.allowed) {
-		ret = pthread_create(&global_apps.ust_listener, NULL,
-				ust_listener_thread, &global_apps);
+		pthread_mutex_lock(&ust_exit_mutex);
+		ret = pthread_create(&local_apps.ust_listener, &thread_attr,
+				ust_listener_thread, &local_apps);
+		if (ret) {
+			ERR("pthread_create local: %s", strerror(ret));
+		}
+		local_apps.thread_active = 1;
+		pthread_mutex_unlock(&ust_exit_mutex);
 	} else {
 		handle_register_done(&local_apps);
 	}
+	ret = pthread_attr_destroy(&thread_attr);
+	if (ret) {
+		ERR("pthread_attr_destroy: %s", strerror(ret));
+	}
+
+	/* Restore original signal mask in parent */
+	ret = pthread_sigmask(SIG_SETMASK, &orig_parent_mask, NULL);
+	if (ret) {
+		ERR("pthread_sigmask: %s", strerror(ret));
+	}
 
 	switch (timeout_mode) {
 	case 1:	/* timeout wait */
@@ -816,7 +1562,7 @@ void __attribute__((constructor)) lttng_ust_init(void)
 					&constructor_timeout);
 		} while (ret < 0 && errno == EINTR);
 		if (ret < 0 && errno == ETIMEDOUT) {
-			ERR("Timed out waiting for ltt-sessiond");
+			ERR("Timed out waiting for lttng-sessiond");
 		} else {
 			assert(!ret);
 		}
@@ -835,15 +1581,25 @@ void __attribute__((constructor)) lttng_ust_init(void)
 static
 void lttng_ust_cleanup(int exiting)
 {
-	cleanup_sock_info(&global_apps);
-	if (local_apps.allowed) {
-		cleanup_sock_info(&local_apps);
-	}
+	cleanup_sock_info(&global_apps, exiting);
+	cleanup_sock_info(&local_apps, exiting);
+	/*
+	 * The teardown in this function all affect data structures
+	 * accessed under the UST lock by the listener thread. This
+	 * lock, along with the lttng_ust_comm_should_quit flag, ensure
+	 * that none of these threads are accessing this data at this
+	 * point.
+	 */
 	lttng_ust_abi_exit();
 	lttng_ust_events_exit();
-	ltt_ring_buffer_client_discard_exit();
-	ltt_ring_buffer_client_overwrite_exit();
-	ltt_ring_buffer_metadata_client_exit();
+	lttng_context_exit();
+	lttng_perf_counter_exit();
+	lttng_ring_buffer_client_discard_rt_exit();
+	lttng_ring_buffer_client_discard_exit();
+	lttng_ring_buffer_client_overwrite_rt_exit();
+	lttng_ring_buffer_client_overwrite_exit();
+	lttng_ring_buffer_metadata_client_exit();
+	lttng_ust_baddr_statedump_destroy();
 	exit_tracepoint();
 	if (!exiting) {
 		/* Reinitialize values for fork */
@@ -868,20 +1624,40 @@ void __attribute__((destructor)) lttng_ust_exit(void)
 	 * mutexes to ensure it is not in a mutex critical section when
 	 * pthread_cancel is later called.
 	 */
-	ust_lock();
+	ust_lock_nocheck();
 	lttng_ust_comm_should_quit = 1;
 	ust_unlock();
 
-	ret = pthread_cancel(global_apps.ust_listener);
-	if (ret) {
-		ERR("Error cancelling global ust listener thread");
+	pthread_mutex_lock(&ust_exit_mutex);
+	/* cancel threads */
+	if (global_apps.thread_active) {
+		ret = pthread_cancel(global_apps.ust_listener);
+		if (ret) {
+			ERR("Error cancelling global ust listener thread: %s",
+				strerror(ret));
+		} else {
+			global_apps.thread_active = 0;
+		}
 	}
-	if (local_apps.allowed) {
+	if (local_apps.thread_active) {
 		ret = pthread_cancel(local_apps.ust_listener);
 		if (ret) {
-			ERR("Error cancelling local ust listener thread");
+			ERR("Error cancelling local ust listener thread: %s",
+				strerror(ret));
+		} else {
+			local_apps.thread_active = 0;
 		}
 	}
+	pthread_mutex_unlock(&ust_exit_mutex);
+
+	/*
+	 * Do NOT join threads: use of sys_futex makes it impossible to
+	 * join the threads without using async-cancel, but async-cancel
+	 * is delivered by a signal, which could hit the target thread
+	 * anywhere in its code path, including while the ust_lock() is
+	 * held, causing a deadlock for the other thread. Let the OS
+	 * cleanup the threads if there are stalled in a syscall.
+	 */
 	lttng_ust_cleanup(1);
 }
 
@@ -903,13 +1679,18 @@ void ust_before_fork(sigset_t *save_sigset)
 	sigset_t all_sigs;
 	int ret;
 
+	if (URCU_TLS(lttng_ust_nest_count))
+		return;
 	/* Disable signals */
 	sigfillset(&all_sigs);
 	ret = sigprocmask(SIG_BLOCK, &all_sigs, save_sigset);
 	if (ret == -1) {
 		PERROR("sigprocmask");
 	}
-	ust_lock();
+
+	pthread_mutex_lock(&ust_fork_mutex);
+
+	ust_lock_nocheck();
 	rcu_bp_before_fork();
 }
 
@@ -919,6 +1700,9 @@ static void ust_after_fork_common(sigset_t *restore_sigset)
 
 	DBG("process %d", getpid());
 	ust_unlock();
+
+	pthread_mutex_unlock(&ust_fork_mutex);
+
 	/* Restore signals */
 	ret = sigprocmask(SIG_SETMASK, restore_sigset, NULL);
 	if (ret == -1) {
@@ -928,6 +1712,8 @@ static void ust_after_fork_common(sigset_t *restore_sigset)
 
 void ust_after_fork_parent(sigset_t *restore_sigset)
 {
+	if (URCU_TLS(lttng_ust_nest_count))
+		return;
 	DBG("process %d", getpid());
 	rcu_bp_after_fork_parent();
 	/* Release mutexes and reenable signals */
@@ -945,6 +1731,8 @@ void ust_after_fork_parent(sigset_t *restore_sigset)
  */
 void ust_after_fork_child(sigset_t *restore_sigset)
 {
+	if (URCU_TLS(lttng_ust_nest_count))
+		return;
 	DBG("process %d", getpid());
 	/* Release urcu mutexes */
 	rcu_bp_after_fork_child();
@@ -954,3 +1742,9 @@ void ust_after_fork_child(sigset_t *restore_sigset)
 	ust_after_fork_common(restore_sigset);
 	lttng_ust_init();
 }
+
+void lttng_ust_sockinfo_session_enabled(void *owner)
+{
+	struct sock_info *sock_info = owner;
+	sock_info->statedump_pending = 1;
+}