X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fcmd.c;h=33ab492daf330eacacc239646b866b612d5975e8;hp=d2673a9019044a40af39341795c42f566d3ce03f;hb=b11feea58d73a097e4e1447473798822da28a70d;hpb=da6c3a50492fd90c5dec03183ce504228292bb3b

diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c
index d2673a901..33ab492da 100644
--- a/src/bin/lttng-sessiond/cmd.c
+++ b/src/bin/lttng-sessiond/cmd.c
@@ -16,6 +16,7 @@
  */
 
 #define _GNU_SOURCE
+#define _LGPL_SOURCE
 #include <assert.h>
 #include <inttypes.h>
 #include <urcu/list.h>
@@ -35,6 +36,7 @@
 #include "kernel-consumer.h"
 #include "lttng-sessiond.h"
 #include "utils.h"
+#include "syscall.h"
 
 #include "cmd.h"
 
@@ -47,6 +49,21 @@
 static pthread_mutex_t relayd_net_seq_idx_lock = PTHREAD_MUTEX_INITIALIZER;
 static uint64_t relayd_net_seq_idx;
 
+/*
+ * Both functions below are special case for the Kernel domain when
+ * enabling/disabling all events.
+ */
+static
+int enable_kevent_all(struct ltt_session *session,
+		struct lttng_domain *domain, char *channel_name,
+		struct lttng_event *event,
+		char *filter_expression,
+		struct lttng_filter_bytecode *filter, int wpipe);
+static
+int disable_kevent_all(struct ltt_session *session, int domain,
+		char *channel_name,
+		struct lttng_event *event);
+
 /*
  * Create a session path used by list_lttng_sessions for the case that the
  * session consumer is on the network.
@@ -203,7 +220,9 @@ static int list_lttng_agent_events(struct agent *agt,
 
 	DBG3("Listing agent events");
 
+	rcu_read_lock();
 	nb_event = lttng_ht_get_count(agt->events);
+	rcu_read_unlock();
 	if (nb_event == 0) {
 		ret = nb_event;
 		goto error;
@@ -345,7 +364,8 @@ static int list_lttng_kernel_events(char *channel_name,
 	DBG("Listing events for channel %s", kchan->channel->name);
 
 	if (nb_event == 0) {
-		goto end;
+		*events = NULL;
+		goto syscall;
 	}
 
 	*events = zmalloc(nb_event * sizeof(struct lttng_event));
@@ -392,7 +412,19 @@ static int list_lttng_kernel_events(char *channel_name,
 		i++;
 	}
 
-end:
+syscall:
+	if (syscall_table) {
+		ssize_t new_size;
+
+		new_size = syscall_list_channel(kchan, events, nb_event);
+		if (new_size < 0) {
+			free(events);
+			ret = -new_size;
+			goto error;
+		}
+		nb_event = new_size;
+	}
+
 	return nb_event;
 
 error:
@@ -1000,9 +1032,24 @@ error:
  * Command LTTNG_DISABLE_EVENT processed by the client thread.
  */
 int cmd_disable_event(struct ltt_session *session, int domain,
-		char *channel_name, char *event_name)
+		char *channel_name,
+		struct lttng_event *event)
 {
 	int ret;
+	char *event_name;
+
+	DBG("Disable event command for event \'%s\'", event->name);
+
+	event_name = event->name;
+
+	if (event->loglevel_type || event->loglevel || event->enabled
+			|| event->pid || event->filter || event->exclusion) {
+		return LTTNG_ERR_UNK;
+	}
+	/* Special handling for kernel domain all events. */
+	if (domain == LTTNG_DOMAIN_KERNEL && !strcmp(event_name, "*")) {
+		return disable_kevent_all(session, domain, channel_name, event);
+	}
 
 	rcu_read_lock();
 
@@ -1030,8 +1077,22 @@ int cmd_disable_event(struct ltt_session *session, int domain,
 			goto error;
 		}
 
-		ret = event_kernel_disable_tracepoint(kchan, event_name);
-		if (ret != LTTNG_OK) {
+		switch (event->type) {
+		case LTTNG_EVENT_ALL:
+		case LTTNG_EVENT_TRACEPOINT:
+			ret = event_kernel_disable_tracepoint(kchan, event_name);
+			if (ret != LTTNG_OK) {
+				goto error;
+			}
+			break;
+		case LTTNG_EVENT_SYSCALL:
+			ret = event_kernel_disable_syscall(kchan, event_name);
+			if (ret != LTTNG_OK) {
+				goto error;
+			}
+			break;
+		default:
+			ret = LTTNG_ERR_UNK;
 			goto error;
 		}
 
@@ -1062,8 +1123,15 @@ int cmd_disable_event(struct ltt_session *session, int domain,
 			goto error;
 		}
 
-		ret = event_ust_disable_tracepoint(usess, uchan, event_name);
-		if (ret != LTTNG_OK) {
+		switch (event->type) {
+		case LTTNG_EVENT_ALL:
+			ret = event_ust_disable_tracepoint(usess, uchan, event_name);
+			if (ret != LTTNG_OK) {
+				goto error;
+			}
+			break;
+		default:
+			ret = LTTNG_ERR_UNK;
 			goto error;
 		}
 
@@ -1073,19 +1141,32 @@ int cmd_disable_event(struct ltt_session *session, int domain,
 	}
 	case LTTNG_DOMAIN_LOG4J:
 	case LTTNG_DOMAIN_JUL:
+	case LTTNG_DOMAIN_PYTHON:
 	{
 		struct agent *agt;
 		struct ltt_ust_session *usess = session->ust_session;
 
 		assert(usess);
 
+		switch (event->type) {
+		case LTTNG_EVENT_ALL:
+			break;
+		default:
+			ret = LTTNG_ERR_UNK;
+			goto error;
+		}
+
 		agt = trace_ust_find_agent(usess, domain);
 		if (!agt) {
 			ret = -LTTNG_ERR_UST_EVENT_NOT_FOUND;
 			goto error;
 		}
-
-		ret = event_agent_disable(usess, agt, event_name);
+		/* The wild card * means that everything should be disabled. */
+		if (strncmp(event->name, "*", 1) == 0 && strlen(event->name) == 1) {
+			ret = event_agent_disable_all(usess, agt);
+		} else {
+			ret = event_agent_disable(usess, agt, event_name);
+		}
 		if (ret != LTTNG_OK) {
 			goto error;
 		}
@@ -1110,10 +1191,12 @@ error:
 }
 
 /*
- * Command LTTNG_DISABLE_ALL_EVENT processed by the client thread.
+ * Command LTTNG_DISABLE_EVENT for event "*" processed by the client thread.
  */
-int cmd_disable_event_all(struct ltt_session *session, int domain,
-		char *channel_name)
+static
+int disable_kevent_all(struct ltt_session *session, int domain,
+		char *channel_name,
+		struct lttng_event *event)
 {
 	int ret;
 
@@ -1143,73 +1226,27 @@ int cmd_disable_event_all(struct ltt_session *session, int domain,
 			goto error;
 		}
 
-		ret = event_kernel_disable_all(kchan);
-		if (ret != LTTNG_OK) {
+		switch (event->type) {
+		case LTTNG_EVENT_ALL:
+			ret = event_kernel_disable_all(kchan);
+			if (ret != LTTNG_OK) {
+				goto error;
+			}
+			break;
+		case LTTNG_EVENT_SYSCALL:
+			ret = event_kernel_disable_syscall(kchan, "");
+			if (ret != LTTNG_OK) {
+				goto error;
+			}
+			break;
+		default:
+			ret = LTTNG_ERR_UNK;
 			goto error;
 		}
 
 		kernel_wait_quiescent(kernel_tracer_fd);
 		break;
 	}
-	case LTTNG_DOMAIN_UST:
-	{
-		struct ltt_ust_session *usess;
-		struct ltt_ust_channel *uchan;
-
-		usess = session->ust_session;
-
-		/*
-		 * If a non-default channel has been created in the
-		 * session, explicitely require that -c chan_name needs
-		 * to be provided.
-		 */
-		if (usess->has_non_default_channel && channel_name[0] == '\0') {
-			ret = LTTNG_ERR_NEED_CHANNEL_NAME;
-			goto error;
-		}
-
-		uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
-				channel_name);
-		if (uchan == NULL) {
-			ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
-			goto error;
-		}
-
-		ret = event_ust_disable_all_tracepoints(usess, uchan);
-		if (ret != 0) {
-			goto error;
-		}
-
-		DBG3("Disable all UST events in channel %s completed", channel_name);
-
-		break;
-	}
-	case LTTNG_DOMAIN_LOG4J:
-	case LTTNG_DOMAIN_JUL:
-	{
-		struct agent *agt;
-		struct ltt_ust_session *usess = session->ust_session;
-
-		assert(usess);
-
-		agt = trace_ust_find_agent(usess, domain);
-		if (!agt) {
-			ret = -LTTNG_ERR_UST_EVENT_NOT_FOUND;
-			goto error;
-		}
-
-		ret = event_agent_disable_all(usess, agt);
-		if (ret != LTTNG_OK) {
-			goto error;
-		}
-
-		break;
-	}
-#if 0
-	case LTTNG_DOMAIN_UST_EXEC_NAME:
-	case LTTNG_DOMAIN_UST_PID:
-	case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
-#endif
 	default:
 		ret = LTTNG_ERR_UND;
 		goto error;
@@ -1351,6 +1388,7 @@ end:
 
 /*
  * Command LTTNG_ENABLE_EVENT processed by the client thread.
+ * We own filter, exclusion, and filter_expression.
  */
 int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
 		char *channel_name, struct lttng_event *event,
@@ -1366,6 +1404,14 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
 	assert(event);
 	assert(channel_name);
 
+	DBG("Enable event command for event \'%s\'", event->name);
+
+	/* Special handling for kernel domain all events. */
+	if (domain->type == LTTNG_DOMAIN_KERNEL && !strcmp(event->name, "*")) {
+		return enable_kevent_all(session, domain, channel_name, event,
+				filter_expression, filter, wpipe);
+	}
+
 	ret = validate_event_name(event->name);
 	if (ret) {
 		goto error;
@@ -1419,12 +1465,29 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
 			goto error;
 		}
 
-		ret = event_kernel_enable_tracepoint(kchan, event);
-		if (ret != LTTNG_OK) {
-			if (channel_created) {
-				/* Let's not leak a useless channel. */
-				kernel_destroy_channel(kchan);
+		switch (event->type) {
+		case LTTNG_EVENT_ALL:
+		case LTTNG_EVENT_PROBE:
+		case LTTNG_EVENT_FUNCTION:
+		case LTTNG_EVENT_FUNCTION_ENTRY:
+		case LTTNG_EVENT_TRACEPOINT:
+			ret = event_kernel_enable_tracepoint(kchan, event);
+			if (ret != LTTNG_OK) {
+				if (channel_created) {
+					/* Let's not leak a useless channel. */
+					kernel_destroy_channel(kchan);
+				}
+				goto error;
 			}
+			break;
+		case LTTNG_EVENT_SYSCALL:
+			ret = event_kernel_enable_syscall(kchan, event->name);
+			if (ret != LTTNG_OK) {
+				goto error;
+			}
+			break;
+		default:
+			ret = LTTNG_ERR_UNK;
 			goto error;
 		}
 
@@ -1477,6 +1540,10 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
 		/* At this point, the session and channel exist on the tracer */
 		ret = event_ust_enable_tracepoint(usess, uchan, event,
 				filter_expression, filter, exclusion);
+		/* We have passed ownership */
+		filter_expression = NULL;
+		filter = NULL;
+		exclusion = NULL;
 		if (ret != LTTNG_OK) {
 			goto error;
 		}
@@ -1484,6 +1551,7 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
 	}
 	case LTTNG_DOMAIN_LOG4J:
 	case LTTNG_DOMAIN_JUL:
+	case LTTNG_DOMAIN_PYTHON:
 	{
 		const char *default_event_name, *default_chan_name;
 		struct agent *agt;
@@ -1523,14 +1591,45 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
 		memcpy(&tmp_dom, domain, sizeof(tmp_dom));
 		tmp_dom.type = LTTNG_DOMAIN_UST;
 
-		if (domain->type == LTTNG_DOMAIN_LOG4J) {
+		switch (domain->type) {
+		case LTTNG_DOMAIN_LOG4J:
 			default_chan_name = DEFAULT_LOG4J_CHANNEL_NAME;
-		} else {
+			break;
+		case LTTNG_DOMAIN_JUL:
 			default_chan_name = DEFAULT_JUL_CHANNEL_NAME;
+			break;
+		case LTTNG_DOMAIN_PYTHON:
+			default_chan_name = DEFAULT_PYTHON_CHANNEL_NAME;
+			break;
+		default:
+			/* The switch/case we are in should avoid this else big problem */
+			assert(0);
+		}
+
+		{
+			struct lttng_filter_bytecode *filter_copy = NULL;
+
+			if (filter) {
+				filter_copy = zmalloc(
+					sizeof(struct lttng_filter_bytecode)
+					+ filter->len);
+				if (!filter_copy) {
+					goto error;
+				}
+
+				memcpy(filter_copy, filter,
+					sizeof(struct lttng_filter_bytecode)
+					+ filter->len);
+			}
+
+			ret = cmd_enable_event(session, &tmp_dom,
+					(char *) default_chan_name,
+					&uevent, filter_expression, filter_copy,
+					NULL, wpipe);
+			/* We have passed ownership */
+			filter_expression = NULL;
 		}
 
-		ret = cmd_enable_event(session, &tmp_dom, (char *) default_chan_name,
-			&uevent, filter_expression, filter, NULL, wpipe);
 		if (ret != LTTNG_OK && ret != LTTNG_ERR_UST_EVENT_ENABLED) {
 			goto error;
 		}
@@ -1538,8 +1637,10 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
 		/* The wild card * means that everything should be enabled. */
 		if (strncmp(event->name, "*", 1) == 0 && strlen(event->name) == 1) {
 			ret = event_agent_enable_all(usess, agt, event, filter);
+			filter = NULL;
 		} else {
 			ret = event_agent_enable(usess, agt, event, filter);
+			filter = NULL;
 		}
 		if (ret != LTTNG_OK) {
 			goto error;
@@ -1560,15 +1661,20 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
 	ret = LTTNG_OK;
 
 error:
+	free(filter_expression);
+	free(filter);
+	free(exclusion);
 	rcu_read_unlock();
 	return ret;
 }
 
 /*
- * Command LTTNG_ENABLE_ALL_EVENT processed by the client thread.
+ * Command LTTNG_ENABLE_EVENT for event "*" processed by the client thread.
  */
-int cmd_enable_event_all(struct ltt_session *session,
-		struct lttng_domain *domain, char *channel_name, int event_type,
+static
+int enable_kevent_all(struct ltt_session *session,
+		struct lttng_domain *domain, char *channel_name,
+		struct lttng_event *event,
 		char *filter_expression,
 		struct lttng_filter_bytecode *filter, int wpipe)
 {
@@ -1623,9 +1729,12 @@ int cmd_enable_event_all(struct ltt_session *session,
 			assert(kchan);
 		}
 
-		switch (event_type) {
+		switch (event->type) {
 		case LTTNG_EVENT_SYSCALL:
-			ret = event_kernel_enable_all_syscalls(kchan, kernel_tracer_fd);
+			ret = event_kernel_enable_syscall(kchan, "");
+			if (ret != LTTNG_OK) {
+				goto error;
+			}
 			break;
 		case LTTNG_EVENT_TRACEPOINT:
 			/*
@@ -1655,98 +1764,6 @@ int cmd_enable_event_all(struct ltt_session *session,
 		kernel_wait_quiescent(kernel_tracer_fd);
 		break;
 	}
-	case LTTNG_DOMAIN_UST:
-	{
-		struct ltt_ust_channel *uchan;
-		struct ltt_ust_session *usess = session->ust_session;
-
-		assert(usess);
-
-		/*
-		 * If a non-default channel has been created in the
-		 * session, explicitely require that -c chan_name needs
-		 * to be provided.
-		 */
-		if (usess->has_non_default_channel && channel_name[0] == '\0') {
-			ret = LTTNG_ERR_NEED_CHANNEL_NAME;
-			goto error;
-		}
-
-		/* Get channel from global UST domain */
-		uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
-				channel_name);
-		if (uchan == NULL) {
-			/* Create default channel */
-			attr = channel_new_default_attr(LTTNG_DOMAIN_UST,
-					usess->buffer_type);
-			if (attr == NULL) {
-				ret = LTTNG_ERR_FATAL;
-				goto error;
-			}
-			strncpy(attr->name, channel_name, sizeof(attr->name));
-
-			ret = cmd_enable_channel(session, domain, attr, wpipe);
-			if (ret != LTTNG_OK) {
-				free(attr);
-				goto error;
-			}
-			free(attr);
-
-			/* Get the newly created channel reference back */
-			uchan = trace_ust_find_channel_by_name(
-					usess->domain_global.channels, channel_name);
-			assert(uchan);
-		}
-
-		/* At this point, the session and channel exist on the tracer */
-
-		switch (event_type) {
-		case LTTNG_EVENT_ALL:
-		case LTTNG_EVENT_TRACEPOINT:
-			ret = event_ust_enable_all_tracepoints(usess, uchan,
-				filter_expression, filter);
-			if (ret != LTTNG_OK) {
-				goto error;
-			}
-			break;
-		default:
-			ret = LTTNG_ERR_UST_ENABLE_FAIL;
-			goto error;
-		}
-
-		/* Manage return value */
-		if (ret != LTTNG_OK) {
-			goto error;
-		}
-
-		break;
-	}
-	case LTTNG_DOMAIN_LOG4J:
-	case LTTNG_DOMAIN_JUL:
-	{
-		struct lttng_event event;
-		struct ltt_ust_session *usess = session->ust_session;
-
-		assert(usess);
-
-		event.loglevel = LTTNG_LOGLEVEL_JUL_ALL;
-		event.loglevel_type = LTTNG_EVENT_LOGLEVEL_ALL;
-		strncpy(event.name, "*", sizeof(event.name));
-		event.name[sizeof(event.name) - 1] = '\0';
-
-		ret = cmd_enable_event(session, domain, NULL, &event,
-				filter_expression, filter, NULL, wpipe);
-		if (ret != LTTNG_OK && ret != LTTNG_ERR_UST_EVENT_ENABLED) {
-			goto error;
-		}
-
-		break;
-	}
-#if 0
-	case LTTNG_DOMAIN_UST_EXEC_NAME:
-	case LTTNG_DOMAIN_UST_PID:
-	case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
-#endif
 	default:
 		ret = LTTNG_ERR_UND;
 		goto error;
@@ -1785,6 +1802,7 @@ ssize_t cmd_list_tracepoints(int domain, struct lttng_event **events)
 		break;
 	case LTTNG_DOMAIN_LOG4J:
 	case LTTNG_DOMAIN_JUL:
+	case LTTNG_DOMAIN_PYTHON:
 		nb_events = agent_list_events(events, domain);
 		if (nb_events < 0) {
 			ret = LTTNG_ERR_UST_LIST_FAIL;
@@ -1833,6 +1851,11 @@ error:
 	return -ret;
 }
 
+ssize_t cmd_list_syscalls(struct lttng_event **events)
+{
+	return syscall_table_list(events);
+}
+
 /*
  * Command LTTNG_START_TRACE processed by the client thread.
  */
@@ -1860,7 +1883,9 @@ int cmd_start_trace(struct ltt_session *session)
 	 * possible to enable channel thus inform the client.
 	 */
 	if (usess && usess->domain_global.channels) {
+		rcu_read_lock();
 		nb_chan += lttng_ht_get_count(usess->domain_global.channels);
+		rcu_read_unlock();
 	}
 	if (ksession) {
 		nb_chan += ksession->channel_count;
@@ -2392,12 +2417,18 @@ ssize_t cmd_list_domains(struct ltt_session *session,
 		DBG3("Listing domains found UST global domain");
 		nb_dom++;
 
+		rcu_read_lock();
 		cds_lfht_for_each_entry(session->ust_session->agents->ht, &iter.iter,
 				agt, node.node) {
 			if (agt->being_used) {
 				nb_dom++;
 			}
 		}
+		rcu_read_unlock();
+	}
+
+	if (!nb_dom) {
+		goto end;
 	}
 
 	*domains = zmalloc(nb_dom * sizeof(struct lttng_domain));
@@ -2416,6 +2447,7 @@ ssize_t cmd_list_domains(struct ltt_session *session,
 		(*domains)[index].buf_type = session->ust_session->buffer_type;
 		index++;
 
+		rcu_read_lock();
 		cds_lfht_for_each_entry(session->ust_session->agents->ht, &iter.iter,
 				agt, node.node) {
 			if (agt->being_used) {
@@ -2424,8 +2456,9 @@ ssize_t cmd_list_domains(struct ltt_session *session,
 				index++;
 			}
 		}
+		rcu_read_unlock();
 	}
-
+end:
 	return nb_dom;
 
 error:
@@ -2455,16 +2488,18 @@ ssize_t cmd_list_channels(int domain, struct ltt_session *session,
 		break;
 	case LTTNG_DOMAIN_UST:
 		if (session->ust_session != NULL) {
+			rcu_read_lock();
 			nb_chan = lttng_ht_get_count(
-					session->ust_session->domain_global.channels);
+				session->ust_session->domain_global.channels);
+			rcu_read_unlock();
 		}
 		DBG3("Number of UST global channels %zd", nb_chan);
-		if (nb_chan <= 0) {
+		if (nb_chan < 0) {
 			ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+			goto error;
 		}
 		break;
 	default:
-		*channels = NULL;
 		ret = LTTNG_ERR_UND;
 		goto error;
 	}
@@ -2477,10 +2512,6 @@ ssize_t cmd_list_channels(int domain, struct ltt_session *session,
 		}
 
 		list_lttng_channels(domain, session, *channels);
-	} else {
-		*channels = NULL;
-		/* Ret value was set in the domain switch case */
-		goto error;
 	}
 
 	return nb_chan;
@@ -2516,14 +2547,17 @@ ssize_t cmd_list_events(int domain, struct ltt_session *session,
 	}
 	case LTTNG_DOMAIN_LOG4J:
 	case LTTNG_DOMAIN_JUL:
+	case LTTNG_DOMAIN_PYTHON:
 		if (session->ust_session) {
 			struct lttng_ht_iter iter;
 			struct agent *agt;
 
+			rcu_read_lock();
 			cds_lfht_for_each_entry(session->ust_session->agents->ht,
 					&iter.iter, agt, node.node) {
 				nb_event = list_lttng_agent_events(agt, events);
 			}
+			rcu_read_unlock();
 		}
 		break;
 	default:
@@ -2772,7 +2806,7 @@ ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
 		struct lttng_snapshot_output **outputs)
 {
 	int ret, idx = 0;
-	struct lttng_snapshot_output *list;
+	struct lttng_snapshot_output *list = NULL;
 	struct lttng_ht_iter iter;
 	struct snapshot_output *output;
 
@@ -2786,7 +2820,7 @@ ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
 	 * set in no output mode.
 	 */
 	if (session->output_traces) {
-		ret = LTTNG_ERR_EPERM;
+		ret = -LTTNG_ERR_EPERM;
 		goto error;
 	}
 
@@ -2797,11 +2831,12 @@ ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
 
 	list = zmalloc(session->snapshot.nb_output * sizeof(*list));
 	if (!list) {
-		ret = LTTNG_ERR_NOMEM;
+		ret = -LTTNG_ERR_NOMEM;
 		goto error;
 	}
 
 	/* Copy list from session to the new list object. */
+	rcu_read_lock();
 	cds_lfht_for_each_entry(session->snapshot.output_ht->ht, &iter.iter,
 			output, node.node) {
 		assert(output->consumer);
@@ -2816,28 +2851,28 @@ ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
 			ret = uri_to_str_url(&output->consumer->dst.net.control,
 					list[idx].ctrl_url, sizeof(list[idx].ctrl_url));
 			if (ret < 0) {
-				ret = LTTNG_ERR_NOMEM;
-				goto free_error;
+				ret = -LTTNG_ERR_NOMEM;
+				goto error;
 			}
 
 			/* Data URI. */
 			ret = uri_to_str_url(&output->consumer->dst.net.data,
 					list[idx].data_url, sizeof(list[idx].data_url));
 			if (ret < 0) {
-				ret = LTTNG_ERR_NOMEM;
-				goto free_error;
+				ret = -LTTNG_ERR_NOMEM;
+				goto error;
 			}
 		}
 		idx++;
 	}
 
 	*outputs = list;
-	return session->snapshot.nb_output;
-
-free_error:
-	free(list);
+	list = NULL;
+	ret = session->snapshot.nb_output;
 error:
-	return -ret;
+	free(list);
+	rcu_read_unlock();
+	return ret;
 }
 
 /*
@@ -3030,12 +3065,14 @@ static uint64_t get_session_max_subbuf_size(struct ltt_session *session)
 		struct ltt_ust_channel *uchan;
 		struct ltt_ust_session *usess = session->ust_session;
 
+		rcu_read_lock();
 		cds_lfht_for_each_entry(usess->domain_global.channels->ht, &iter.iter,
 				uchan, node.node) {
 			if (uchan->attr.subbuf_size > max_size) {
 				max_size = uchan->attr.subbuf_size;
 			}
 		}
+		rcu_read_unlock();
 	}
 
 	return max_size;
@@ -3082,6 +3119,7 @@ int cmd_snapshot_record(struct ltt_session *session,
 	uint64_t session_max_size = 0, max_stream_size = 0;
 
 	assert(session);
+	assert(output);
 
 	DBG("Cmd snapshot record for session %s", session->name);
 
@@ -3101,7 +3139,7 @@ int cmd_snapshot_record(struct ltt_session *session,
 	}
 
 	/* Use temporary output for the session. */
-	if (output && *output->ctrl_url != '\0') {
+	if (*output->ctrl_url != '\0') {
 		ret = snapshot_output_init(output->max_size, output->name,
 				output->ctrl_url, output->data_url, session->consumer,
 				&tmp_output, NULL);