X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust%2Flttng-ust-comm.c;h=a1ebcbe6fc83564a5fc4d9c0c0642403938da35f;hb=8c90a710949a214d87084ff67fc85f284bc93ef2;hp=86cce18d57fe658588db907ed8016f39e95f975f;hpb=08114193d6fd56309b520ae50e7117b8bc7f34a5;p=lttng-ust.git

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index 86cce18d..a1ebcbe6 100644
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -41,11 +41,16 @@
 #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"
 
 /*
  * Has lttng ust comm constructor been called ?
@@ -77,6 +82,12 @@ 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.
  */
@@ -87,6 +98,7 @@ struct sock_info {
 	int constructor_sem_posted;
 	int allowed;
 	int global;
+	int thread_active;
 
 	char sock_path[PATH_MAX];
 	int socket;
@@ -102,6 +114,7 @@ struct sock_info global_apps = {
 
 	.root_handle = -1,
 	.allowed = 1,
+	.thread_active = 0,
 
 	.sock_path = DEFAULT_GLOBAL_APPS_UNIX_SOCK,
 	.socket = -1,
@@ -116,18 +129,75 @@ struct sock_info local_apps = {
 	.global = 0,
 	.root_handle = -1,
 	.allowed = 0,	/* Check setuid bit first */
+	.thread_active = 0,
 
 	.socket = -1,
 };
 
 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",
+};
+
+extern void lttng_ring_buffer_client_overwrite_init(void);
+extern void lttng_ring_buffer_client_discard_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_discard_exit(void);
+extern void lttng_ring_buffer_metadata_client_exit(void);
+
+/*
+ * 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 print_cmd(int cmd, int handle)
+{
+	const char *cmd_name = "Unknown";
+
+	if (cmd_name_mapping[cmd]) {
+		cmd_name = cmd_name_mapping[cmd];
+	}
+	DBG("Message Received \"%s\", Handle \"%s\" (%d)", cmd_name,
+		lttng_ust_obj_get_name(handle), handle);
+}
 
 static
 int setup_local_apps(void)
@@ -140,14 +210,16 @@ 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)
+	if (!home_dir) {
+		WARN("HOME environment variable not set. Disabling LTTng-UST per-user tracing.");
+		assert(local_apps.allowed == 0);
 		return -ENOENT;
+	}
+	local_apps.allowed = 1;
 	snprintf(local_apps.sock_path, PATH_MAX,
 		 DEFAULT_HOME_APPS_UNIX_SOCK, home_dir);
 	snprintf(local_apps.wait_shm_path, PATH_MAX,
@@ -195,15 +267,15 @@ 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;
 	}
 }
 
@@ -233,15 +305,15 @@ 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;
 	union ust_args args;
+	ssize_t len;
 
 	ust_lock();
 
 	memset(&lur, 0, sizeof(lur));
 
 	if (lttng_ust_comm_should_quit) {
-		ret = -EPERM;
+		ret = -LTTNG_UST_ERR_EXITING;
 		goto end;
 	}
 
@@ -264,11 +336,136 @@ int handle_message(struct sock_info *sock_info,
 		else
 			ret = lttng_ust_objd_unref(lum->handle);
 		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;
+				goto end;
+			} else {
+				DBG("incorrect filter data message size: %zd", len);
+				ret = -EINVAL;
+				free(bytecode);
+				goto end;
+			}
+		}
+		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_CHANNEL:
+	{
+		void *chan_data;
+
+		len = ustcomm_recv_channel_from_sessiond(sock,
+				&chan_data, lum->u.channel.len);
+		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 end;
+			} else {
+				DBG("incorrect channel data message size: %zd", len);
+				ret = -EINVAL;
+				goto end;
+			}
+		}
+		args.channel.chan_data = chan_data;
+		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 end;
+		}
+		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,
-					&args);
+					&args, sock_info);
 		else
 			ret = -ENOSYS;
 		break;
@@ -279,101 +476,75 @@ end:
 	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 = *args.stream.memory_map_size;
-		shm_fd = *args.stream.shm_fd;
-		wait_fd = *args.stream.wait_fd;
-		break;
-	case LTTNG_UST_METADATA:
-	case LTTNG_UST_CHANNEL:
-		lur.u.channel.memory_map_size = *args.channel.memory_map_size;
-		shm_fd = *args.channel.shm_fd;
-		wait_fd = *args.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;
-		}
-	}
 	/*
-	 * We still have the memory map reference, and the fds have been
-	 * sent to the sessiond. We can therefore close those fds. Note
-	 * that we keep the write side of the wait_fd open, but close
-	 * the read side.
+	 * LTTNG_UST_TRACEPOINT_FIELD_LIST_GET needs to send the field
+	 * after the reply.
 	 */
-	if (lur.ret_code == USTCOMM_OK) {
+	if (lur.ret_code == LTTNG_UST_OK) {
 		switch (lum->cmd) {
-		case LTTNG_UST_STREAM:
-			if (shm_fd >= 0) {
-				ret = close(shm_fd);
-				if (ret) {
-					PERROR("Error closing stream shm_fd");
-				}
-				*args.stream.shm_fd = -1;
+		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 (wait_fd >= 0) {
-				ret = close(wait_fd);
-				if (ret) {
-					PERROR("Error closing stream wait_fd");
-				}
-				*args.stream.wait_fd = -1;
+			if (len != sizeof(args.field_list.entry)) {
+				ret = -EINVAL;
+				goto error;
 			}
-			break;
-		case LTTNG_UST_METADATA:
-		case LTTNG_UST_CHANNEL:
-			if (shm_fd >= 0) {
-				ret = close(shm_fd);
-				if (ret) {
-					PERROR("Error closing channel shm_fd");
-				}
-				*args.channel.shm_fd = -1;
-			}
-			if (wait_fd >= 0) {
-				ret = close(wait_fd);
-				if (ret) {
-					PERROR("Error closing channel wait_fd");
-				}
-				*args.channel.wait_fd = -1;
-			}
-			break;
 		}
 	}
 
@@ -388,7 +559,7 @@ void cleanup_sock_info(struct sock_info *sock_info, int exiting)
 	int ret;
 
 	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");
 		}
@@ -451,7 +622,9 @@ int get_wait_shm(struct sock_info *sock_info, size_t mmap_size)
 	 * If the open failed because the file did not exist, try
 	 * creating it ourself.
 	 */
+	URCU_TLS(lttng_ust_nest_count)++;
 	pid = fork();
+	URCU_TLS(lttng_ust_nest_count)--;
 	if (pid > 0) {
 		int status;
 
@@ -500,9 +673,9 @@ 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
@@ -514,13 +687,13 @@ 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;
 	}
@@ -634,7 +807,7 @@ 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
@@ -663,12 +836,11 @@ restart:
 	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);
 		}
@@ -694,13 +866,13 @@ restart:
 
 	/*
 	 * 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;
@@ -728,8 +900,11 @@ 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);
+			DBG("%s lttng-sessiond has performed an orderly shutdown", sock_info->name);
 			ust_lock();
+			if (lttng_ust_comm_should_quit) {
+				goto quit;
+			}
 			/*
 			 * Either sessiond has shutdown or refused us by closing the socket.
 			 * In either case, we don't want to delay construction execution,
@@ -745,28 +920,39 @@ 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) {
+			if (ret) {
 				ERR("Error handling message for %s socket", sock_info->name);
 			}
 			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:
+	ust_lock();
+	if (lttng_ust_comm_should_quit) {
+		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:
+	sock_info->thread_active = 0;
+	ust_unlock();
 	return NULL;
 }
 
@@ -814,17 +1000,27 @@ int get_timeout(struct timespec *constructor_timeout)
  * 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_ringbuffer_tls();
+	lttng_fixup_vtid_tls();
+	lttng_fixup_nest_count_tls();
+	lttng_fixup_procname_tls();
+
 	/*
 	 * We want precise control over the order in which we construct
 	 * our sub-libraries vs starting to receive commands from
@@ -833,9 +1029,9 @@ 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_ring_buffer_metadata_client_init();
+	lttng_ring_buffer_client_overwrite_init();
+	lttng_ring_buffer_client_discard_init();
 
 	timeout_mode = get_timeout(&constructor_timeout);
 
@@ -844,17 +1040,60 @@ void __attribute__((constructor)) lttng_ust_init(void)
 
 	ret = setup_local_apps();
 	if (ret) {
-		ERR("Error setting up to local apps");
+		DBG("local apps setup returned %d", ret);
+	}
+
+	/* 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_create(&local_apps.ust_listener, NULL,
-			ust_listener_thread, &local_apps);
+
+	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));
+	}
+
+	ust_lock();
+	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;
+	ust_unlock();
 
 	if (local_apps.allowed) {
-		ret = pthread_create(&global_apps.ust_listener, NULL,
-				ust_listener_thread, &global_apps);
+		ust_lock();
+		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;
+		ust_unlock();
 	} 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 */
@@ -863,7 +1102,7 @@ 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);
 		}
@@ -895,9 +1134,9 @@ void lttng_ust_cleanup(int exiting)
 	 */
 	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_ring_buffer_client_discard_exit();
+	lttng_ring_buffer_client_overwrite_exit();
+	lttng_ring_buffer_metadata_client_exit();
 	exit_tracepoint();
 	if (!exiting) {
 		/* Reinitialize values for fork */
@@ -924,19 +1163,28 @@ void __attribute__((destructor)) lttng_ust_exit(void)
 	 */
 	ust_lock();
 	lttng_ust_comm_should_quit = 1;
-	ust_unlock();
 
 	/* cancel threads */
-	ret = pthread_cancel(global_apps.ust_listener);
-	if (ret) {
-		ERR("Error cancelling global ust listener thread");
+	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;
 		}
 	}
+	ust_unlock();
+
 	/*
 	 * Do NOT join threads: use of sys_futex makes it impossible to
 	 * join the threads without using async-cancel, but async-cancel
@@ -966,6 +1214,8 @@ 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);
@@ -991,6 +1241,8 @@ 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 */
@@ -1008,6 +1260,8 @@ 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();