Docs: add comment to cmd_add_context()
[lttng-tools.git] / src / bin / lttng-sessiond / cmd.c
index 46a758e27eab8f9b01c502256bde42a60b32702d..8e06ce6913875dd85e0a17e0eeafb929ba93d425 100644 (file)
@@ -1,5 +1,6 @@
 /*
  * Copyright (C) 2012 - David Goulet <dgoulet@efficios.com>
+ * Copyright (C) 2016 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License, version 2 only, as
@@ -15,8 +16,9 @@
  * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#define _GNU_SOURCE
+#define _LGPL_SOURCE
 #include <assert.h>
+#include <inttypes.h>
 #include <urcu/list.h>
 #include <urcu/uatomic.h>
 
 #include <common/common.h>
 #include <common/sessiond-comm/sessiond-comm.h>
 #include <common/relayd/relayd.h>
+#include <common/utils.h>
+#include <common/compat/string.h>
 
 #include "channel.h"
 #include "consumer.h"
 #include "event.h"
+#include "health-sessiond.h"
 #include "kernel.h"
 #include "kernel-consumer.h"
 #include "lttng-sessiond.h"
 #include "utils.h"
+#include "syscall.h"
+#include "agent.h"
 
 #include "cmd.h"
 
 /*
  * Used to keep a unique index for each relayd socket created where this value
  * is associated with streams on the consumer so it can match the right relayd
- * to send to.
- *
- * This value should be incremented atomically for safety purposes and future
- * possible concurrent access.
+ * to send to. It must be accessed with the relayd_net_seq_idx_lock
+ * held.
  */
-static unsigned int relayd_net_seq_idx;
+static pthread_mutex_t relayd_net_seq_idx_lock = PTHREAD_MUTEX_INITIALIZER;
+static uint64_t relayd_net_seq_idx;
+
+static int validate_event_name(const char *);
+static int validate_ust_event_name(const char *);
+static int cmd_enable_event_internal(struct ltt_session *session,
+               struct lttng_domain *domain,
+               char *channel_name, struct lttng_event *event,
+               char *filter_expression,
+               struct lttng_filter_bytecode *filter,
+               struct lttng_event_exclusion *exclusion,
+               int wpipe);
 
 /*
  * Create a session path used by list_lttng_sessions for the case that the
@@ -101,11 +117,22 @@ static int build_network_session_path(char *dst, size_t size,
                goto error;
        }
 
-       if (strlen(tmp_uurl) > 0) {
+       /*
+        * Do we have a UST url set. If yes, this means we have both kernel and UST
+        * to print.
+        */
+       if (*tmp_uurl != '\0') {
                ret = snprintf(dst, size, "[K]: %s [data: %d] -- [U]: %s [data: %d]",
                                tmp_urls, kdata_port, tmp_uurl, udata_port);
        } else {
-               ret = snprintf(dst, size, "%s [data: %d]", tmp_urls, kdata_port);
+               int dport;
+               if (kuri || (!kuri && !uuri)) {
+                       dport = kdata_port;
+               } else {
+                       /* No kernel URI, use the UST port. */
+                       dport = udata_port;
+               }
+               ret = snprintf(dst, size, "%s [data: %d]", tmp_urls, dport);
        }
 
 error:
@@ -115,8 +142,8 @@ error:
 /*
  * Fill lttng_channel array of all channels.
  */
-static void list_lttng_channels(int domain, struct ltt_session *session,
-               struct lttng_channel *channels)
+static void list_lttng_channels(enum lttng_domain_type domain,
+               struct ltt_session *session, struct lttng_channel *channels)
 {
        int i = 0;
        struct ltt_kernel_channel *kchan;
@@ -141,6 +168,7 @@ static void list_lttng_channels(int domain, struct ltt_session *session,
                struct lttng_ht_iter iter;
                struct ltt_ust_channel *uchan;
 
+               rcu_read_lock();
                cds_lfht_for_each_entry(session->ust_session->domain_global.channels->ht,
                                &iter.iter, uchan, node.node) {
                        strncpy(channels[i].name, uchan->name, LTTNG_SYMBOL_NAME_LEN);
@@ -152,6 +180,8 @@ static void list_lttng_channels(int domain, struct ltt_session *session,
                        channels[i].attr.read_timer_interval =
                                uchan->attr.read_timer_interval;
                        channels[i].enabled = uchan->enabled;
+                       channels[i].attr.tracefile_size = uchan->tracefile_size;
+                       channels[i].attr.tracefile_count = uchan->tracefile_count;
                        switch (uchan->attr.output) {
                        case LTTNG_UST_MMAP:
                        default:
@@ -160,6 +190,7 @@ static void list_lttng_channels(int domain, struct ltt_session *session,
                        }
                        i++;
                }
+               rcu_read_unlock();
                break;
        }
        default:
@@ -167,6 +198,59 @@ static void list_lttng_channels(int domain, struct ltt_session *session,
        }
 }
 
+/*
+ * Create a list of agent domain events.
+ *
+ * Return number of events in list on success or else a negative value.
+ */
+static int list_lttng_agent_events(struct agent *agt,
+               struct lttng_event **events)
+{
+       int i = 0, ret = 0;
+       unsigned int nb_event = 0;
+       struct agent_event *event;
+       struct lttng_event *tmp_events;
+       struct lttng_ht_iter iter;
+
+       assert(agt);
+       assert(events);
+
+       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;
+       }
+
+       tmp_events = zmalloc(nb_event * sizeof(*tmp_events));
+       if (!tmp_events) {
+               PERROR("zmalloc agent events session");
+               ret = -LTTNG_ERR_FATAL;
+               goto error;
+       }
+
+       rcu_read_lock();
+       cds_lfht_for_each_entry(agt->events->ht, &iter.iter, event, node.node) {
+               strncpy(tmp_events[i].name, event->name, sizeof(tmp_events[i].name));
+               tmp_events[i].name[sizeof(tmp_events[i].name) - 1] = '\0';
+               tmp_events[i].enabled = event->enabled;
+               tmp_events[i].loglevel = event->loglevel_value;
+               tmp_events[i].loglevel_type = event->loglevel_type;
+               i++;
+       }
+       rcu_read_unlock();
+
+       *events = tmp_events;
+       ret = nb_event;
+
+error:
+       assert(nb_event == i);
+       return ret;
+}
+
 /*
  * Create a list of ust global domain events.
  */
@@ -194,8 +278,7 @@ static int list_lttng_ust_global_events(char *channel_name,
 
        uchan = caa_container_of(&node->node, struct ltt_ust_channel, node.node);
 
-       nb_event += lttng_ht_get_count(uchan->events);
-
+       nb_event = lttng_ht_get_count(uchan->events);
        if (nb_event == 0) {
                ret = nb_event;
                goto error;
@@ -210,6 +293,11 @@ static int list_lttng_ust_global_events(char *channel_name,
        }
 
        cds_lfht_for_each_entry(uchan->events->ht, &iter.iter, uevent, node.node) {
+               if (uevent->internal) {
+                       /* This event should remain hidden from clients */
+                       nb_event--;
+                       continue;
+               }
                strncpy(tmp[i].name, uevent->attr.name, LTTNG_SYMBOL_NAME_LEN);
                tmp[i].name[LTTNG_SYMBOL_NAME_LEN - 1] = '\0';
                tmp[i].enabled = uevent->enabled;
@@ -241,6 +329,9 @@ static int list_lttng_ust_global_events(char *channel_name,
                if (uevent->filter) {
                        tmp[i].filter = 1;
                }
+               if (uevent->exclusion) {
+                       tmp[i].exclusion = 1;
+               }
                i++;
        }
 
@@ -274,7 +365,8 @@ 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));
@@ -288,13 +380,19 @@ static int list_lttng_kernel_events(char *channel_name,
                strncpy((*events)[i].name, event->event->name, LTTNG_SYMBOL_NAME_LEN);
                (*events)[i].name[LTTNG_SYMBOL_NAME_LEN - 1] = '\0';
                (*events)[i].enabled = event->enabled;
+               (*events)[i].filter =
+                               (unsigned char) !!event->filter_expression;
 
                switch (event->event->instrumentation) {
                case LTTNG_KERNEL_TRACEPOINT:
                        (*events)[i].type = LTTNG_EVENT_TRACEPOINT;
                        break;
-               case LTTNG_KERNEL_KPROBE:
                case LTTNG_KERNEL_KRETPROBE:
+                       (*events)[i].type = LTTNG_EVENT_FUNCTION;
+                       memcpy(&(*events)[i].attr.probe, &event->event->u.kprobe,
+                                       sizeof(struct lttng_kernel_kprobe));
+                       break;
+               case LTTNG_KERNEL_KPROBE:
                        (*events)[i].type = LTTNG_EVENT_PROBE;
                        memcpy(&(*events)[i].attr.probe, &event->event->u.kprobe,
                                        sizeof(struct lttng_kernel_kprobe));
@@ -317,7 +415,19 @@ 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:
@@ -330,7 +440,8 @@ error:
  * domain adding the default trace directory.
  */
 static int add_uri_to_consumer(struct consumer_output *consumer,
-               struct lttng_uri *uri, int domain, const char *session_name)
+               struct lttng_uri *uri, enum lttng_domain_type domain,
+               const char *session_name)
 {
        int ret = LTTNG_OK;
        const char *default_trace_dir;
@@ -363,16 +474,31 @@ static int add_uri_to_consumer(struct consumer_output *consumer,
        case LTTNG_DST_IPV6:
                DBG2("Setting network URI to consumer");
 
+               if (consumer->type == CONSUMER_DST_NET) {
+                       if ((uri->stype == LTTNG_STREAM_CONTROL &&
+                               consumer->dst.net.control_isset) ||
+                               (uri->stype == LTTNG_STREAM_DATA &&
+                               consumer->dst.net.data_isset)) {
+                               ret = LTTNG_ERR_URL_EXIST;
+                               goto error;
+                       }
+               } else {
+                       memset(&consumer->dst.net, 0, sizeof(consumer->dst.net));
+               }
+
+               consumer->type = CONSUMER_DST_NET;
+
                /* Set URI into consumer output object */
                ret = consumer_set_network_uri(consumer, uri);
                if (ret < 0) {
-                       ret = LTTNG_ERR_FATAL;
+                       ret = -ret;
                        goto error;
                } else if (ret == 1) {
                        /*
                         * URI was the same in the consumer so we do not append the subdir
                         * again so to not duplicate output dir.
                         */
+                       ret = LTTNG_OK;
                        goto error;
                }
 
@@ -407,6 +533,8 @@ static int add_uri_to_consumer(struct consumer_output *consumer,
                break;
        }
 
+       ret = LTTNG_OK;
+
 error:
        return ret;
 }
@@ -422,14 +550,13 @@ static int init_kernel_tracing(struct ltt_kernel_session *session)
 
        assert(session);
 
+       rcu_read_lock();
+
        if (session->consumer_fds_sent == 0 && session->consumer != NULL) {
                cds_lfht_for_each_entry(session->consumer->socks->ht, &iter.iter,
                                socket, node.node) {
-                       /* Code flow error */
-                       assert(socket->fd >= 0);
-
                        pthread_mutex_lock(socket->lock);
-                       ret = kernel_consumer_send_session(socket->fd, session);
+                       ret = kernel_consumer_send_session(socket, session);
                        pthread_mutex_unlock(socket->lock);
                        if (ret < 0) {
                                ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
@@ -439,6 +566,7 @@ static int init_kernel_tracing(struct ltt_kernel_session *session)
        }
 
 error:
+       rcu_read_unlock();
        return ret;
 }
 
@@ -448,28 +576,27 @@ error:
  * On success, the relayd_sock pointer is set to the created socket.
  * Else, it's stays untouched and a lttcomm error code is returned.
  */
-static int create_connect_relayd(struct consumer_output *output,
-               const char *session_name, struct lttng_uri *uri,
-               struct lttcomm_sock **relayd_sock)
+static int create_connect_relayd(struct lttng_uri *uri,
+               struct lttcomm_relayd_sock **relayd_sock)
 {
        int ret;
-       struct lttcomm_sock *sock;
-
-       /* Create socket object from URI */
-       sock = lttcomm_alloc_sock_from_uri(uri);
-       if (sock == NULL) {
-               ret = LTTNG_ERR_FATAL;
-               goto error;
-       }
+       struct lttcomm_relayd_sock *rsock;
 
-       ret = lttcomm_create_sock(sock);
-       if (ret < 0) {
+       rsock = lttcomm_alloc_relayd_sock(uri, RELAYD_VERSION_COMM_MAJOR,
+                       RELAYD_VERSION_COMM_MINOR);
+       if (!rsock) {
                ret = LTTNG_ERR_FATAL;
                goto error;
        }
 
-       /* Connect to relayd so we can proceed with a session creation. */
-       ret = relayd_connect(sock);
+       /*
+        * Connect to relayd so we can proceed with a session creation. This call
+        * can possibly block for an arbitrary amount of time to set the health
+        * state to be in poll execution.
+        */
+       health_poll_entry();
+       ret = relayd_connect(rsock);
+       health_poll_exit();
        if (ret < 0) {
                ERR("Unable to reach lttng-relayd");
                ret = LTTNG_ERR_RELAYD_CONNECT_FAIL;
@@ -481,8 +608,7 @@ static int create_connect_relayd(struct consumer_output *output,
                DBG3("Creating relayd stream socket from URI");
 
                /* Check relayd version */
-               ret = relayd_version_check(sock, RELAYD_VERSION_COMM_MAJOR,
-                               RELAYD_VERSION_COMM_MINOR);
+               ret = relayd_version_check(rsock);
                if (ret < 0) {
                        ret = LTTNG_ERR_RELAYD_VERSION_FAIL;
                        goto close_sock;
@@ -496,18 +622,15 @@ static int create_connect_relayd(struct consumer_output *output,
                goto close_sock;
        }
 
-       *relayd_sock = sock;
+       *relayd_sock = rsock;
 
        return LTTNG_OK;
 
 close_sock:
-       if (sock) {
-               (void) relayd_close(sock);
-       }
+       /* The returned value is not useful since we are on an error path. */
+       (void) relayd_close(rsock);
 free_sock:
-       if (sock) {
-               lttcomm_destroy_sock(sock);
-       }
+       free(rsock);
 error:
        return ret;
 }
@@ -515,39 +638,38 @@ error:
 /*
  * Connect to the relayd using URI and send the socket to the right consumer.
  */
-static int send_consumer_relayd_socket(int domain, struct ltt_session *session,
-               struct lttng_uri *relayd_uri, struct consumer_output *consumer,
-               int consumer_fd)
+static int send_consumer_relayd_socket(enum lttng_domain_type domain,
+               unsigned int session_id, struct lttng_uri *relayd_uri,
+               struct consumer_output *consumer,
+               struct consumer_socket *consumer_sock,
+               char *session_name, char *hostname, int session_live_timer)
 {
        int ret;
-       struct lttcomm_sock *sock = NULL;
+       struct lttcomm_relayd_sock *rsock = NULL;
+
+       /* Connect to relayd and make version check if uri is the control. */
+       ret = create_connect_relayd(relayd_uri, &rsock);
+       if (ret != LTTNG_OK) {
+               goto error;
+       }
+       assert(rsock);
 
        /* Set the network sequence index if not set. */
-       if (consumer->net_seq_index == -1) {
+       if (consumer->net_seq_index == (uint64_t) -1ULL) {
+               pthread_mutex_lock(&relayd_net_seq_idx_lock);
                /*
                 * Increment net_seq_idx because we are about to transfer the
                 * new relayd socket to the consumer.
+                * Assign unique key so the consumer can match streams.
                 */
-               uatomic_inc(&relayd_net_seq_idx);
-               /* Assign unique key so the consumer can match streams */
-               uatomic_set(&consumer->net_seq_index,
-                               uatomic_read(&relayd_net_seq_idx));
-       }
-
-       /* Connect to relayd and make version check if uri is the control. */
-       ret = create_connect_relayd(consumer, session->name, relayd_uri, &sock);
-       if (ret != LTTNG_OK) {
-               goto close_sock;
-       }
-
-       /* If the control socket is connected, network session is ready */
-       if (relayd_uri->stype == LTTNG_STREAM_CONTROL) {
-               session->net_handle = 1;
+               consumer->net_seq_index = ++relayd_net_seq_idx;
+               pthread_mutex_unlock(&relayd_net_seq_idx_lock);
        }
 
        /* Send relayd socket to consumer. */
-       ret = consumer_send_relayd_socket(consumer_fd, sock,
-                       consumer, relayd_uri->stype);
+       ret = consumer_send_relayd_socket(consumer_sock, rsock, consumer,
+                       relayd_uri->stype, session_id,
+                       session_name, hostname, session_live_timer);
        if (ret < 0) {
                ret = LTTNG_ERR_ENABLE_CONSUMER_FAIL;
                goto close_sock;
@@ -555,9 +677,9 @@ static int send_consumer_relayd_socket(int domain, struct ltt_session *session,
 
        /* Flag that the corresponding socket was sent. */
        if (relayd_uri->stype == LTTNG_STREAM_CONTROL) {
-               consumer->dst.net.control_sock_sent = 1;
+               consumer_sock->control_sock_sent = 1;
        } else if (relayd_uri->stype == LTTNG_STREAM_DATA) {
-               consumer->dst.net.data_sock_sent = 1;
+               consumer_sock->data_sock_sent = 1;
        }
 
        ret = LTTNG_OK;
@@ -568,11 +690,18 @@ static int send_consumer_relayd_socket(int domain, struct ltt_session *session,
         */
 
 close_sock:
-       if (sock) {
-               (void) relayd_close(sock);
-               lttcomm_destroy_sock(sock);
-       }
+       (void) relayd_close(rsock);
+       free(rsock);
 
+error:
+       if (ret != LTTNG_OK) {
+               /*
+                * The consumer output for this session should not be used anymore
+                * since the relayd connection failed thus making any tracing or/and
+                * streaming not usable.
+                */
+               consumer->enabled = 0;
+       }
        return ret;
 }
 
@@ -581,27 +710,31 @@ close_sock:
  * helper function to facilitate sending the information to the consumer for a
  * session.
  */
-static int send_consumer_relayd_sockets(int domain,
-               struct ltt_session *session, struct consumer_output *consumer, int fd)
+static int send_consumer_relayd_sockets(enum lttng_domain_type domain,
+               unsigned int session_id, struct consumer_output *consumer,
+               struct consumer_socket *sock, char *session_name,
+               char *hostname, int session_live_timer)
 {
        int ret = LTTNG_OK;
 
-       assert(session);
        assert(consumer);
+       assert(sock);
 
        /* Sending control relayd socket. */
-       if (!consumer->dst.net.control_sock_sent) {
-               ret = send_consumer_relayd_socket(domain, session,
-                               &consumer->dst.net.control, consumer, fd);
+       if (!sock->control_sock_sent) {
+               ret = send_consumer_relayd_socket(domain, session_id,
+                               &consumer->dst.net.control, consumer, sock,
+                               session_name, hostname, session_live_timer);
                if (ret != LTTNG_OK) {
                        goto error;
                }
        }
 
        /* Sending data relayd socket. */
-       if (!consumer->dst.net.data_sock_sent) {
-               ret = send_consumer_relayd_socket(domain, session,
-                               &consumer->dst.net.data, consumer, fd);
+       if (!sock->data_sock_sent) {
+               ret = send_consumer_relayd_socket(domain, session_id,
+                               &consumer->dst.net.data, consumer, sock,
+                               session_name, hostname, session_live_timer);
                if (ret != LTTNG_OK) {
                        goto error;
                }
@@ -616,7 +749,7 @@ error:
  * the relayd and send them to the right domain consumer. Consumer type MUST be
  * network.
  */
-static int setup_relayd(struct ltt_session *session)
+int cmd_setup_relayd(struct ltt_session *session)
 {
        int ret = LTTNG_OK;
        struct ltt_ust_session *usess;
@@ -629,23 +762,26 @@ static int setup_relayd(struct ltt_session *session)
        usess = session->ust_session;
        ksess = session->kernel_session;
 
-       DBG2("Setting relayd for session %s", session->name);
+       DBG("Setting relayd for session %s", session->name);
+
+       rcu_read_lock();
 
        if (usess && usess->consumer && usess->consumer->type == CONSUMER_DST_NET
                        && usess->consumer->enabled) {
                /* For each consumer socket, send relayd sockets */
                cds_lfht_for_each_entry(usess->consumer->socks->ht, &iter.iter,
                                socket, node.node) {
-                       /* Code flow error */
-                       assert(socket->fd >= 0);
-
                        pthread_mutex_lock(socket->lock);
-                       ret = send_consumer_relayd_sockets(LTTNG_DOMAIN_UST, session,
-                                       usess->consumer, socket->fd);
+                       ret = send_consumer_relayd_sockets(LTTNG_DOMAIN_UST, session->id,
+                                       usess->consumer, socket,
+                                       session->name, session->hostname,
+                                       session->live_timer);
                        pthread_mutex_unlock(socket->lock);
                        if (ret != LTTNG_OK) {
                                goto error;
                        }
+                       /* Session is now ready for network streaming. */
+                       session->net_handle = 1;
                }
        }
 
@@ -653,19 +789,86 @@ static int setup_relayd(struct ltt_session *session)
                        && ksess->consumer->enabled) {
                cds_lfht_for_each_entry(ksess->consumer->socks->ht, &iter.iter,
                                socket, node.node) {
-                       /* Code flow error */
-                       assert(socket->fd >= 0);
-
                        pthread_mutex_lock(socket->lock);
-                       ret = send_consumer_relayd_sockets(LTTNG_DOMAIN_KERNEL, session,
-                                       ksess->consumer, socket->fd);
+                       ret = send_consumer_relayd_sockets(LTTNG_DOMAIN_KERNEL, session->id,
+                                       ksess->consumer, socket,
+                                       session->name, session->hostname,
+                                       session->live_timer);
                        pthread_mutex_unlock(socket->lock);
                        if (ret != LTTNG_OK) {
                                goto error;
                        }
+                       /* Session is now ready for network streaming. */
+                       session->net_handle = 1;
+               }
+       }
+
+error:
+       rcu_read_unlock();
+       return ret;
+}
+
+/*
+ * Start a kernel session by opening all necessary streams.
+ */
+static int start_kernel_session(struct ltt_kernel_session *ksess, int wpipe)
+{
+       int ret;
+       struct ltt_kernel_channel *kchan;
+
+       /* Open kernel metadata */
+       if (ksess->metadata == NULL && ksess->output_traces) {
+               ret = kernel_open_metadata(ksess);
+               if (ret < 0) {
+                       ret = LTTNG_ERR_KERN_META_FAIL;
+                       goto error;
+               }
+       }
+
+       /* Open kernel metadata stream */
+       if (ksess->metadata && ksess->metadata_stream_fd < 0) {
+               ret = kernel_open_metadata_stream(ksess);
+               if (ret < 0) {
+                       ERR("Kernel create metadata stream failed");
+                       ret = LTTNG_ERR_KERN_STREAM_FAIL;
+                       goto error;
+               }
+       }
+
+       /* For each channel */
+       cds_list_for_each_entry(kchan, &ksess->channel_list.head, list) {
+               if (kchan->stream_count == 0) {
+                       ret = kernel_open_channel_stream(kchan);
+                       if (ret < 0) {
+                               ret = LTTNG_ERR_KERN_STREAM_FAIL;
+                               goto error;
+                       }
+                       /* Update the stream global counter */
+                       ksess->stream_count_global += ret;
                }
        }
 
+       /* Setup kernel consumer socket and send fds to it */
+       ret = init_kernel_tracing(ksess);
+       if (ret != 0) {
+               ret = LTTNG_ERR_KERN_START_FAIL;
+               goto error;
+       }
+
+       /* This start the kernel tracing */
+       ret = kernel_start_session(ksess);
+       if (ret < 0) {
+               ret = LTTNG_ERR_KERN_START_FAIL;
+               goto error;
+       }
+
+       /* Quiescent wait after starting trace */
+       kernel_wait_quiescent(kernel_tracer_fd);
+
+       ksess->active = 1;
+
+       ret = LTTNG_OK;
+
 error:
        return ret;
 }
@@ -673,14 +876,16 @@ error:
 /*
  * Command LTTNG_DISABLE_CHANNEL processed by the client thread.
  */
-int cmd_disable_channel(struct ltt_session *session, int domain,
-               char *channel_name)
+int cmd_disable_channel(struct ltt_session *session,
+               enum lttng_domain_type domain, char *channel_name)
 {
        int ret;
        struct ltt_ust_session *usess;
 
        usess = session->ust_session;
 
+       rcu_read_lock();
+
        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
        {
@@ -706,17 +911,12 @@ int cmd_disable_channel(struct ltt_session *session, int domain,
                        goto error;
                }
 
-               ret = channel_ust_disable(usess, domain, uchan);
+               ret = channel_ust_disable(usess, uchan);
                if (ret != LTTNG_OK) {
                        goto error;
                }
                break;
        }
-#if 0
-       case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
-       case LTTNG_DOMAIN_UST_EXEC_NAME:
-       case LTTNG_DOMAIN_UST_PID:
-#endif
        default:
                ret = LTTNG_ERR_UNKNOWN_DOMAIN;
                goto error;
@@ -725,42 +925,30 @@ int cmd_disable_channel(struct ltt_session *session, int domain,
        ret = LTTNG_OK;
 
 error:
+       rcu_read_unlock();
        return ret;
 }
 
 /*
- * Command LTTNG_ENABLE_CHANNEL processed by the client thread.
+ * Command LTTNG_TRACK_PID processed by the client thread.
  *
- * The wpipe arguments is used as a notifier for the kernel thread.
+ * Called with session lock held.
  */
-int cmd_enable_channel(struct ltt_session *session,
-               int domain, struct lttng_channel *attr, int wpipe)
+int cmd_track_pid(struct ltt_session *session, enum lttng_domain_type domain,
+               int pid)
 {
        int ret;
-       struct ltt_ust_session *usess = session->ust_session;
-       struct lttng_ht *chan_ht;
-
-       assert(session);
-       assert(attr);
 
-       DBG("Enabling channel %s for session %s", attr->name, session->name);
+       rcu_read_lock();
 
        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
        {
-               struct ltt_kernel_channel *kchan;
-
-               /* Mandatory for a kernel channel. */
-               assert(wpipe > 0);
+               struct ltt_kernel_session *ksess;
 
-               kchan = trace_kernel_get_channel_by_name(attr->name,
-                               session->kernel_session);
-               if (kchan == NULL) {
-                       ret = channel_kernel_create(session->kernel_session, attr, wpipe);
-               } else {
-                       ret = channel_kernel_enable(session->kernel_session, kchan);
-               }
+               ksess = session->kernel_session;
 
+               ret = kernel_track_pid(ksess, pid);
                if (ret != LTTNG_OK) {
                        goto error;
                }
@@ -770,56 +958,48 @@ int cmd_enable_channel(struct ltt_session *session,
        }
        case LTTNG_DOMAIN_UST:
        {
-               struct ltt_ust_channel *uchan;
+               struct ltt_ust_session *usess;
 
-               chan_ht = usess->domain_global.channels;
+               usess = session->ust_session;
 
-               uchan = trace_ust_find_channel_by_name(chan_ht, attr->name);
-               if (uchan == NULL) {
-                       ret = channel_ust_create(usess, domain, attr);
-               } else {
-                       ret = channel_ust_enable(usess, domain, uchan);
+               ret = trace_ust_track_pid(usess, pid);
+               if (ret != LTTNG_OK) {
+                       goto error;
                }
                break;
        }
-#if 0
-       case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
-       case LTTNG_DOMAIN_UST_EXEC_NAME:
-       case LTTNG_DOMAIN_UST_PID:
-#endif
        default:
                ret = LTTNG_ERR_UNKNOWN_DOMAIN;
                goto error;
        }
 
+       ret = LTTNG_OK;
+
 error:
+       rcu_read_unlock();
        return ret;
 }
 
-
 /*
- * Command LTTNG_DISABLE_EVENT processed by the client thread.
+ * Command LTTNG_UNTRACK_PID processed by the client thread.
+ *
+ * Called with session lock held.
  */
-int cmd_disable_event(struct ltt_session *session, int domain,
-               char *channel_name, char *event_name)
+int cmd_untrack_pid(struct ltt_session *session, enum lttng_domain_type domain,
+               int pid)
 {
        int ret;
 
+       rcu_read_lock();
+
        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
        {
-               struct ltt_kernel_channel *kchan;
                struct ltt_kernel_session *ksess;
 
                ksess = session->kernel_session;
 
-               kchan = trace_kernel_get_channel_by_name(channel_name, ksess);
-               if (kchan == NULL) {
-                       ret = LTTNG_ERR_KERN_CHAN_NOT_FOUND;
-                       goto error;
-               }
-
-               ret = event_kernel_disable_tracepoint(ksess, kchan, event_name);
+               ret = kernel_untrack_pid(ksess, pid);
                if (ret != LTTNG_OK) {
                        goto error;
                }
@@ -829,66 +1009,103 @@ int cmd_disable_event(struct ltt_session *session, int domain,
        }
        case LTTNG_DOMAIN_UST:
        {
-               struct ltt_ust_channel *uchan;
                struct ltt_ust_session *usess;
 
                usess = session->ust_session;
 
-               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_tracepoint(usess, domain, uchan, event_name);
+               ret = trace_ust_untrack_pid(usess, pid);
                if (ret != LTTNG_OK) {
                        goto error;
                }
-
-               DBG3("Disable UST event %s in channel %s completed", event_name,
-                               channel_name);
                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;
+               ret = LTTNG_ERR_UNKNOWN_DOMAIN;
                goto error;
        }
 
        ret = LTTNG_OK;
 
 error:
+       rcu_read_unlock();
        return ret;
 }
 
 /*
- * Command LTTNG_DISABLE_ALL_EVENT processed by the client thread.
+ * Command LTTNG_ENABLE_CHANNEL processed by the client thread.
+ *
+ * The wpipe arguments is used as a notifier for the kernel thread.
  */
-int cmd_disable_event_all(struct ltt_session *session, int domain,
-               char *channel_name)
+int cmd_enable_channel(struct ltt_session *session,
+               struct lttng_domain *domain, struct lttng_channel *attr, int wpipe)
 {
        int ret;
+       struct ltt_ust_session *usess = session->ust_session;
+       struct lttng_ht *chan_ht;
+       size_t len;
 
-       switch (domain) {
+       assert(session);
+       assert(attr);
+       assert(domain);
+
+       len = lttng_strnlen(attr->name, sizeof(attr->name));
+
+       /* Validate channel name */
+       if (attr->name[0] == '.' ||
+               memchr(attr->name, '/', len) != NULL) {
+               ret = LTTNG_ERR_INVALID_CHANNEL_NAME;
+               goto end;
+       }
+
+       DBG("Enabling channel %s for session %s", attr->name, session->name);
+
+       rcu_read_lock();
+
+       /*
+        * Don't try to enable a channel if the session has been started at
+        * some point in time before. The tracer does not allow it.
+        */
+       if (session->has_been_started) {
+               ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
+               goto error;
+       }
+
+       /*
+        * If the session is a live session, remove the switch timer, the
+        * live timer does the same thing but sends also synchronisation
+        * beacons for inactive streams.
+        */
+       if (session->live_timer > 0) {
+               attr->attr.live_timer_interval = session->live_timer;
+               attr->attr.switch_timer_interval = 0;
+       }
+
+       /*
+        * The ringbuffer (both in user space and kernel) behave badly in overwrite
+        * mode and with less than 2 subbuf so block it right away and send back an
+        * invalid attribute error.
+        */
+       if (attr->attr.overwrite && attr->attr.num_subbuf < 2) {
+               ret = LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       switch (domain->type) {
        case LTTNG_DOMAIN_KERNEL:
        {
-               struct ltt_kernel_session *ksess;
                struct ltt_kernel_channel *kchan;
 
-               ksess = session->kernel_session;
-
-               kchan = trace_kernel_get_channel_by_name(channel_name, ksess);
+               kchan = trace_kernel_get_channel_by_name(attr->name,
+                               session->kernel_session);
                if (kchan == NULL) {
-                       ret = LTTNG_ERR_KERN_CHAN_NOT_FOUND;
-                       goto error;
+                       ret = channel_kernel_create(session->kernel_session, attr, wpipe);
+                       if (attr->name[0] != '\0') {
+                               session->kernel_session->has_non_default_channel = 1;
+                       }
+               } else {
+                       ret = channel_kernel_enable(session->kernel_session, kchan);
                }
 
-               ret = event_kernel_disable_all(ksess, kchan);
                if (ret != LTTNG_OK) {
                        goto error;
                }
@@ -897,40 +1114,241 @@ int cmd_disable_event_all(struct ltt_session *session, int domain,
                break;
        }
        case LTTNG_DOMAIN_UST:
+       case LTTNG_DOMAIN_JUL:
+       case LTTNG_DOMAIN_LOG4J:
+       case LTTNG_DOMAIN_PYTHON:
        {
-               struct ltt_ust_session *usess;
                struct ltt_ust_channel *uchan;
 
-               usess = session->ust_session;
-
-               uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
-                               channel_name);
-               if (uchan == NULL) {
+               /*
+                * FIXME
+                *
+                * Current agent implementation limitations force us to allow
+                * only one channel at once in "agent" subdomains. Each
+                * subdomain has a default channel name which must be strictly
+                * adhered to.
+                */
+               if (domain->type == LTTNG_DOMAIN_JUL) {
+                       if (strncmp(attr->name, DEFAULT_JUL_CHANNEL_NAME,
+                                       LTTNG_SYMBOL_NAME_LEN)) {
+                               ret = LTTNG_ERR_INVALID_CHANNEL_NAME;
+                               goto error;
+                       }
+               } else if (domain->type == LTTNG_DOMAIN_LOG4J) {
+                       if (strncmp(attr->name, DEFAULT_LOG4J_CHANNEL_NAME,
+                                       LTTNG_SYMBOL_NAME_LEN)) {
+                               ret = LTTNG_ERR_INVALID_CHANNEL_NAME;
+                               goto error;
+                       }
+               } else if (domain->type == LTTNG_DOMAIN_PYTHON) {
+                       if (strncmp(attr->name, DEFAULT_PYTHON_CHANNEL_NAME,
+                                       LTTNG_SYMBOL_NAME_LEN)) {
+                               ret = LTTNG_ERR_INVALID_CHANNEL_NAME;
+                               goto error;
+                       }
+               }
+
+               chan_ht = usess->domain_global.channels;
+
+               uchan = trace_ust_find_channel_by_name(chan_ht, attr->name);
+               if (uchan == NULL) {
+                       ret = channel_ust_create(usess, attr, domain->buf_type);
+                       if (attr->name[0] != '\0') {
+                               usess->has_non_default_channel = 1;
+                       }
+               } else {
+                       ret = channel_ust_enable(usess, uchan);
+               }
+               break;
+       }
+       default:
+               ret = LTTNG_ERR_UNKNOWN_DOMAIN;
+               goto error;
+       }
+
+error:
+       rcu_read_unlock();
+end:
+       return ret;
+}
+
+/*
+ * Command LTTNG_DISABLE_EVENT processed by the client thread.
+ */
+int cmd_disable_event(struct ltt_session *session,
+               enum lttng_domain_type domain, 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 (validate_event_name(event_name)) {
+               ret = LTTNG_ERR_INVALID_EVENT_NAME;
+               goto error;
+       }
+
+       /* Error out on unhandled search criteria */
+       if (event->loglevel_type || event->loglevel != -1 || event->enabled
+                       || event->pid || event->filter || event->exclusion) {
+               ret = LTTNG_ERR_UNK;
+               goto error;
+       }
+
+       rcu_read_lock();
+
+       switch (domain) {
+       case LTTNG_DOMAIN_KERNEL:
+       {
+               struct ltt_kernel_channel *kchan;
+               struct ltt_kernel_session *ksess;
+
+               ksess = session->kernel_session;
+
+               /*
+                * If a non-default channel has been created in the
+                * session, explicitely require that -c chan_name needs
+                * to be provided.
+                */
+               if (ksess->has_non_default_channel && channel_name[0] == '\0') {
+                       ret = LTTNG_ERR_NEED_CHANNEL_NAME;
+                       goto error_unlock;
+               }
+
+               kchan = trace_kernel_get_channel_by_name(channel_name, ksess);
+               if (kchan == NULL) {
+                       ret = LTTNG_ERR_KERN_CHAN_NOT_FOUND;
+                       goto error_unlock;
+               }
+
+               switch (event->type) {
+               case LTTNG_EVENT_ALL:
+               case LTTNG_EVENT_TRACEPOINT:
+               case LTTNG_EVENT_SYSCALL:
+               case LTTNG_EVENT_PROBE:
+               case LTTNG_EVENT_FUNCTION:
+               case LTTNG_EVENT_FUNCTION_ENTRY:/* fall-through */
+                       if (event_name[0] == '\0') {
+                               ret = event_kernel_disable_event(kchan,
+                                       NULL, event->type);
+                       } else {
+                               ret = event_kernel_disable_event(kchan,
+                                       event_name, event->type);
+                       }
+                       if (ret != LTTNG_OK) {
+                               goto error_unlock;
+                       }
+                       break;
+               default:
+                       ret = LTTNG_ERR_UNK;
+                       goto error_unlock;
+               }
+
+               kernel_wait_quiescent(kernel_tracer_fd);
+               break;
+       }
+       case LTTNG_DOMAIN_UST:
+       {
+               struct ltt_ust_channel *uchan;
+               struct ltt_ust_session *usess;
+
+               usess = session->ust_session;
+
+               if (validate_ust_event_name(event_name)) {
+                       ret = LTTNG_ERR_INVALID_EVENT_NAME;
+                       goto error_unlock;
+               }
+
+               /*
+                * If a non-default channel has been created in the
+                * session, explicitly 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_unlock;
+               }
+
+               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;
+                       goto error_unlock;
                }
 
-               ret = event_ust_disable_all_tracepoints(usess, domain, uchan);
-               if (ret != 0) {
-                       goto error;
+               switch (event->type) {
+               case LTTNG_EVENT_ALL:
+                       /*
+                        * An empty event name means that everything
+                        * should be disabled.
+                        */
+                       if (event->name[0] == '\0') {
+                               ret = event_ust_disable_all_tracepoints(usess, uchan);
+                       } else {
+                               ret = event_ust_disable_tracepoint(usess, uchan,
+                                               event_name);
+                       }
+                       if (ret != LTTNG_OK) {
+                               goto error_unlock;
+                       }
+                       break;
+               default:
+                       ret = LTTNG_ERR_UNK;
+                       goto error_unlock;
+               }
+
+               DBG3("Disable UST event %s in channel %s completed", event_name,
+                               channel_name);
+               break;
+       }
+       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_unlock;
                }
 
-               DBG3("Disable all UST events in channel %s completed", channel_name);
+               agt = trace_ust_find_agent(usess, domain);
+               if (!agt) {
+                       ret = -LTTNG_ERR_UST_EVENT_NOT_FOUND;
+                       goto error_unlock;
+               }
+               /*
+                * An empty event name means that everything
+                * should be disabled.
+                */
+               if (event->name[0] == '\0') {
+                       ret = event_agent_disable_all(usess, agt);
+               } else {
+                       ret = event_agent_disable(usess, agt, event_name);
+               }
+               if (ret != LTTNG_OK) {
+                       goto error_unlock;
+               }
 
                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;
+               goto error_unlock;
        }
 
        ret = LTTNG_OK;
 
+error_unlock:
+       rcu_read_unlock();
 error:
        return ret;
 }
@@ -938,11 +1356,16 @@ error:
 /*
  * Command LTTNG_ADD_CONTEXT processed by the client thread.
  */
-int cmd_add_context(struct ltt_session *session, int domain,
-               char *channel_name, char *event_name, struct lttng_event_context *ctx,
-               int kwpipe)
+int cmd_add_context(struct ltt_session *session, enum lttng_domain_type domain,
+               char *channel_name, struct lttng_event_context *ctx, int kwpipe)
 {
-       int ret;
+       int ret, chan_kern_created = 0, chan_ust_created = 0;
+       char *app_ctx_provider_name = NULL, *app_ctx_name = NULL;
+
+       if (ctx->ctx == LTTNG_EVENT_CONTEXT_APP_CONTEXT) {
+               app_ctx_provider_name = ctx->u.app_ctx.provider_name;
+               app_ctx_name = ctx->u.app_ctx.ctx_name;
+       }
 
        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
@@ -954,125 +1377,231 @@ int cmd_add_context(struct ltt_session *session, int domain,
                        if (ret != LTTNG_OK) {
                                goto error;
                        }
+                       chan_kern_created = 1;
                }
-
                /* Add kernel context to kernel tracer */
-               ret = context_kernel_add(session->kernel_session, ctx,
-                               event_name, channel_name);
+               ret = context_kernel_add(session->kernel_session, ctx, channel_name);
                if (ret != LTTNG_OK) {
                        goto error;
                }
                break;
+       case LTTNG_DOMAIN_JUL:
+       case LTTNG_DOMAIN_LOG4J:
+       {
+               /*
+                * Validate channel name.
+                * If no channel name is given and the domain is JUL or LOG4J,
+                * set it to the appropriate domain-specific channel name. If
+                * a name is provided but does not match the expexted channel
+                * name, return an error.
+                */
+               if (domain == LTTNG_DOMAIN_JUL && *channel_name &&
+                               strcmp(channel_name,
+                               DEFAULT_JUL_CHANNEL_NAME)) {
+                       ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+                       goto error;
+               } else if (domain == LTTNG_DOMAIN_LOG4J && *channel_name &&
+                               strcmp(channel_name,
+                               DEFAULT_LOG4J_CHANNEL_NAME)) {
+                       ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+                       goto error;
+               }
+               /* break is _not_ missing here. */
+       }
        case LTTNG_DOMAIN_UST:
        {
                struct ltt_ust_session *usess = session->ust_session;
+               unsigned int chan_count;
+
                assert(usess);
 
-               unsigned int chan_count =
-                       lttng_ht_get_count(usess->domain_global.channels);
+               chan_count = lttng_ht_get_count(usess->domain_global.channels);
                if (chan_count == 0) {
                        struct lttng_channel *attr;
                        /* Create default channel */
-                       attr = channel_new_default_attr(domain);
+                       attr = channel_new_default_attr(domain, usess->buffer_type);
                        if (attr == NULL) {
                                ret = LTTNG_ERR_FATAL;
                                goto error;
                        }
 
-                       ret = channel_ust_create(usess, domain, attr);
+                       ret = channel_ust_create(usess, attr, usess->buffer_type);
                        if (ret != LTTNG_OK) {
                                free(attr);
                                goto error;
                        }
                        free(attr);
+                       chan_ust_created = 1;
                }
 
-
-               ret = context_ust_add(usess, domain, ctx, event_name, channel_name);
+               ret = context_ust_add(usess, domain, ctx, channel_name);
+               free(app_ctx_provider_name);
+               free(app_ctx_name);
+               app_ctx_name = NULL;
+               app_ctx_provider_name = NULL;
                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;
        }
 
        ret = LTTNG_OK;
+       goto end;
 
 error:
+       if (chan_kern_created) {
+               struct ltt_kernel_channel *kchan =
+                       trace_kernel_get_channel_by_name(DEFAULT_CHANNEL_NAME,
+                                       session->kernel_session);
+               /* Created previously, this should NOT fail. */
+               assert(kchan);
+               kernel_destroy_channel(kchan);
+       }
+
+       if (chan_ust_created) {
+               struct ltt_ust_channel *uchan =
+                       trace_ust_find_channel_by_name(
+                                       session->ust_session->domain_global.channels,
+                                       DEFAULT_CHANNEL_NAME);
+               /* Created previously, this should NOT fail. */
+               assert(uchan);
+               /* Remove from the channel list of the session. */
+               trace_ust_delete_channel(session->ust_session->domain_global.channels,
+                               uchan);
+               trace_ust_destroy_channel(uchan);
+       }
+end:
+       free(app_ctx_provider_name);
+       free(app_ctx_name);
        return ret;
 }
 
-/*
- * Command LTTNG_SET_FILTER processed by the client thread.
- */
-int cmd_set_filter(struct ltt_session *session, int domain,
-               char *channel_name, char *event_name,
-               struct lttng_filter_bytecode *bytecode)
+static int validate_event_name(const char *name)
 {
-       int ret;
-
-       switch (domain) {
-       case LTTNG_DOMAIN_KERNEL:
-               ret = LTTNG_ERR_FATAL;
-               break;
-       case LTTNG_DOMAIN_UST:
-       {
-               struct ltt_ust_session *usess = session->ust_session;
+       int ret = 0;
+       const char *c = name;
+       const char *event_name_end = c + LTTNG_SYMBOL_NAME_LEN;
+       bool null_terminated = false;
 
-               ret = filter_ust_set(usess, domain, bytecode, event_name, channel_name);
-               if (ret != LTTNG_OK) {
-                       goto error;
+       /*
+        * Make sure that unescaped wildcards are only used as the last
+        * character of the event name.
+        */
+       while (c < event_name_end) {
+               switch (*c) {
+               case '\0':
+                       null_terminated = true;
+                       goto end;
+               case '\\':
+                       c++;
+                       break;
+               case '*':
+                       if ((c + 1) < event_name_end && *(c + 1)) {
+                               /* Wildcard is not the last character */
+                               ret = LTTNG_ERR_INVALID_EVENT_NAME;
+                               goto end;
+                       }
+               default:
+                       break;
                }
-               break;
+               c++;
        }
-#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;
+end:
+       if (!ret && !null_terminated) {
+               ret = LTTNG_ERR_INVALID_EVENT_NAME;
        }
-
-       ret = LTTNG_OK;
-
-error:
        return ret;
+}
 
+static inline bool name_starts_with(const char *name, const char *prefix)
+{
+       const size_t max_cmp_len = min(strlen(prefix), LTTNG_SYMBOL_NAME_LEN);
+
+       return !strncmp(name, prefix, max_cmp_len);
 }
 
+/* Perform userspace-specific event name validation */
+static int validate_ust_event_name(const char *name)
+{
+       int ret = 0;
+
+       if (!name) {
+               ret = -1;
+               goto end;
+       }
+
+       /*
+        * Check name against all internal UST event component namespaces used
+        * by the agents.
+        */
+       if (name_starts_with(name, DEFAULT_JUL_EVENT_COMPONENT) ||
+               name_starts_with(name, DEFAULT_LOG4J_EVENT_COMPONENT) ||
+               name_starts_with(name, DEFAULT_PYTHON_EVENT_COMPONENT)) {
+               ret = -1;
+       }
+
+end:
+       return ret;
+}
 
 /*
- * Command LTTNG_ENABLE_EVENT processed by the client thread.
+ * Internal version of cmd_enable_event() with a supplemental
+ * "internal_event" flag which is used to enable internal events which should
+ * be hidden from clients. Such events are used in the agent implementation to
+ * enable the events through which all "agent" events are funeled.
  */
-int cmd_enable_event(struct ltt_session *session, int domain,
-               char *channel_name, struct lttng_event *event, int wpipe)
+static int _cmd_enable_event(struct ltt_session *session,
+               struct lttng_domain *domain,
+               char *channel_name, struct lttng_event *event,
+               char *filter_expression,
+               struct lttng_filter_bytecode *filter,
+               struct lttng_event_exclusion *exclusion,
+               int wpipe, bool internal_event)
 {
-       int ret;
+       int ret, channel_created = 0;
        struct lttng_channel *attr;
 
        assert(session);
        assert(event);
        assert(channel_name);
 
-       switch (domain) {
+       /* If we have a filter, we must have its filter expression */
+       assert(!(!!filter_expression ^ !!filter));
+
+       DBG("Enable event command for event \'%s\'", event->name);
+
+       rcu_read_lock();
+
+       ret = validate_event_name(event->name);
+       if (ret) {
+               goto error;
+       }
+
+       switch (domain->type) {
        case LTTNG_DOMAIN_KERNEL:
        {
                struct ltt_kernel_channel *kchan;
 
+               /*
+                * If a non-default channel has been created in the
+                * session, explicitely require that -c chan_name needs
+                * to be provided.
+                */
+               if (session->kernel_session->has_non_default_channel
+                               && channel_name[0] == '\0') {
+                       ret = LTTNG_ERR_NEED_CHANNEL_NAME;
+                       goto error;
+               }
+
                kchan = trace_kernel_get_channel_by_name(channel_name,
                                session->kernel_session);
                if (kchan == NULL) {
-                       attr = channel_new_default_attr(domain);
+                       attr = channel_new_default_attr(LTTNG_DOMAIN_KERNEL,
+                                       LTTNG_BUFFER_GLOBAL);
                        if (attr == NULL) {
                                ret = LTTNG_ERR_FATAL;
                                goto error;
@@ -1085,6 +1614,8 @@ int cmd_enable_event(struct ltt_session *session, int domain,
                                goto error;
                        }
                        free(attr);
+
+                       channel_created = 1;
                }
 
                /* Get the newly created kernel channel pointer */
@@ -1096,9 +1627,88 @@ int cmd_enable_event(struct ltt_session *session, int domain,
                        goto error;
                }
 
-               ret = event_kernel_enable_tracepoint(session->kernel_session, kchan,
-                               event);
-               if (ret != LTTNG_OK) {
+               switch (event->type) {
+               case LTTNG_EVENT_ALL:
+               {
+                       char *filter_expression_a = NULL;
+                       struct lttng_filter_bytecode *filter_a = NULL;
+
+                       /*
+                        * We need to duplicate filter_expression and filter,
+                        * because ownership is passed to first enable
+                        * event.
+                        */
+                       if (filter_expression) {
+                               filter_expression_a = strdup(filter_expression);
+                               if (!filter_expression_a) {
+                                       ret = LTTNG_ERR_FATAL;
+                                       goto error;
+                               }
+                       }
+                       if (filter) {
+                               filter_a = zmalloc(sizeof(*filter_a) + filter->len);
+                               if (!filter_a) {
+                                       free(filter_expression_a);
+                                       ret = LTTNG_ERR_FATAL;
+                                       goto error;
+                               }
+                               memcpy(filter_a, filter, sizeof(*filter_a) + filter->len);
+                       }
+                       event->type = LTTNG_EVENT_TRACEPOINT;   /* Hack */
+                       ret = event_kernel_enable_event(kchan, event,
+                               filter_expression, filter);
+                       /* We have passed ownership */
+                       filter_expression = NULL;
+                       filter = NULL;
+                       if (ret != LTTNG_OK) {
+                               if (channel_created) {
+                                       /* Let's not leak a useless channel. */
+                                       kernel_destroy_channel(kchan);
+                               }
+                               free(filter_expression_a);
+                               free(filter_a);
+                               goto error;
+                       }
+                       event->type = LTTNG_EVENT_SYSCALL;      /* Hack */
+                       ret = event_kernel_enable_event(kchan, event,
+                               filter_expression_a, filter_a);
+                       /* We have passed ownership */
+                       filter_expression_a = NULL;
+                       filter_a = NULL;
+                       if (ret != LTTNG_OK) {
+                               goto error;
+                       }
+                       break;
+               }
+               case LTTNG_EVENT_PROBE:
+               case LTTNG_EVENT_FUNCTION:
+               case LTTNG_EVENT_FUNCTION_ENTRY:
+               case LTTNG_EVENT_TRACEPOINT:
+                       ret = event_kernel_enable_event(kchan, event,
+                               filter_expression, filter);
+                       /* We have passed ownership */
+                       filter_expression = NULL;
+                       filter = NULL;
+                       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_event(kchan, event,
+                               filter_expression, filter);
+                       /* We have passed ownership */
+                       filter_expression = NULL;
+                       filter = NULL;
+                       if (ret != LTTNG_OK) {
+                               goto error;
+                       }
+                       break;
+               default:
+                       ret = LTTNG_ERR_UNK;
                        goto error;
                }
 
@@ -1112,12 +1722,23 @@ int cmd_enable_event(struct ltt_session *session, int domain,
 
                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(domain);
+                       attr = channel_new_default_attr(LTTNG_DOMAIN_UST,
+                                       usess->buffer_type);
                        if (attr == NULL) {
                                ret = LTTNG_ERR_FATAL;
                                goto error;
@@ -1137,162 +1758,157 @@ int cmd_enable_event(struct ltt_session *session, int domain,
                        assert(uchan);
                }
 
+               if (uchan->domain != LTTNG_DOMAIN_UST && !internal_event) {
+                       /*
+                        * Don't allow users to add UST events to channels which
+                        * are assigned to a userspace subdomain (JUL, Log4J,
+                        * Python, etc.).
+                        */
+                       ret = LTTNG_ERR_INVALID_CHANNEL_DOMAIN;
+                       goto error;
+               }
+
+               if (!internal_event) {
+                       /*
+                        * Ensure the event name is not reserved for internal
+                        * use.
+                        */
+                       ret = validate_ust_event_name(event->name);
+                       if (ret) {
+                               WARN("Userspace event name %s failed validation.",
+                                               event->name ?
+                                               event->name : "NULL");
+                               ret = LTTNG_ERR_INVALID_EVENT_NAME;
+                               goto error;
+                       }
+               }
+
                /* At this point, the session and channel exist on the tracer */
-               ret = event_ust_enable_tracepoint(usess, domain, uchan, event);
-               if (ret != LTTNG_OK) {
+               ret = event_ust_enable_tracepoint(usess, uchan, event,
+                               filter_expression, filter, exclusion,
+                               internal_event);
+               /* We have passed ownership */
+               filter_expression = NULL;
+               filter = NULL;
+               exclusion = NULL;
+               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;
-       }
-
-       ret = LTTNG_OK;
-
-error:
-       return ret;
-}
-
-/*
- * Command LTTNG_ENABLE_ALL_EVENT processed by the client thread.
- */
-int cmd_enable_event_all(struct ltt_session *session, int domain,
-               char *channel_name, int event_type, int wpipe)
-{
-       int ret;
-       struct lttng_channel *attr;
-
-       assert(session);
-       assert(channel_name);
-
-       switch (domain) {
-       case LTTNG_DOMAIN_KERNEL:
+       case LTTNG_DOMAIN_LOG4J:
+       case LTTNG_DOMAIN_JUL:
+       case LTTNG_DOMAIN_PYTHON:
        {
-               struct ltt_kernel_channel *kchan;
-
-               assert(session->kernel_session);
+               const char *default_event_name, *default_chan_name;
+               struct agent *agt;
+               struct lttng_event uevent;
+               struct lttng_domain tmp_dom;
+               struct ltt_ust_session *usess = session->ust_session;
 
-               kchan = trace_kernel_get_channel_by_name(channel_name,
-                               session->kernel_session);
-               if (kchan == NULL) {
-                       /* Create default channel */
-                       attr = channel_new_default_attr(domain);
-                       if (attr == NULL) {
-                               ret = LTTNG_ERR_FATAL;
-                               goto error;
-                       }
-                       strncpy(attr->name, channel_name, sizeof(attr->name));
+               assert(usess);
 
-                       ret = cmd_enable_channel(session, domain, attr, wpipe);
-                       if (ret != LTTNG_OK) {
-                               free(attr);
+               agt = trace_ust_find_agent(usess, domain->type);
+               if (!agt) {
+                       agt = agent_create(domain->type);
+                       if (!agt) {
+                               ret = LTTNG_ERR_NOMEM;
                                goto error;
                        }
-                       free(attr);
+                       agent_add(agt, usess->agents);
+               }
 
-                       /* Get the newly created kernel channel pointer */
-                       kchan = trace_kernel_get_channel_by_name(channel_name,
-                                       session->kernel_session);
-                       assert(kchan);
+               /* Create the default tracepoint. */
+               memset(&uevent, 0, sizeof(uevent));
+               uevent.type = LTTNG_EVENT_TRACEPOINT;
+               uevent.loglevel_type = LTTNG_EVENT_LOGLEVEL_ALL;
+               default_event_name = event_get_default_agent_ust_name(
+                               domain->type);
+               if (!default_event_name) {
+                       ret = LTTNG_ERR_FATAL;
+                       goto error;
                }
+               strncpy(uevent.name, default_event_name, sizeof(uevent.name));
+               uevent.name[sizeof(uevent.name) - 1] = '\0';
 
-               switch (event_type) {
-               case LTTNG_EVENT_SYSCALL:
-                       ret = event_kernel_enable_all_syscalls(session->kernel_session,
-                                       kchan, kernel_tracer_fd);
+               /*
+                * The domain type is changed because we are about to enable the
+                * default channel and event for the JUL domain that are hardcoded.
+                * This happens in the UST domain.
+                */
+               memcpy(&tmp_dom, domain, sizeof(tmp_dom));
+               tmp_dom.type = LTTNG_DOMAIN_UST;
+
+               switch (domain->type) {
+               case LTTNG_DOMAIN_LOG4J:
+                       default_chan_name = DEFAULT_LOG4J_CHANNEL_NAME;
                        break;
-               case LTTNG_EVENT_TRACEPOINT:
-                       /*
-                        * This call enables all LTTNG_KERNEL_TRACEPOINTS and
-                        * events already registered to the channel.
-                        */
-                       ret = event_kernel_enable_all_tracepoints(session->kernel_session,
-                                       kchan, kernel_tracer_fd);
+               case LTTNG_DOMAIN_JUL:
+                       default_chan_name = DEFAULT_JUL_CHANNEL_NAME;
                        break;
-               case LTTNG_EVENT_ALL:
-                       /* Enable syscalls and tracepoints */
-                       ret = event_kernel_enable_all(session->kernel_session,
-                                       kchan, kernel_tracer_fd);
+               case LTTNG_DOMAIN_PYTHON:
+                       default_chan_name = DEFAULT_PYTHON_CHANNEL_NAME;
                        break;
                default:
-                       ret = LTTNG_ERR_KERN_ENABLE_FAIL;
-                       goto error;
+                       /* The switch/case we are in makes this impossible */
+                       assert(0);
                }
 
-               /* Manage return value */
-               if (ret != LTTNG_OK) {
-                       goto error;
-               }
+               {
+                       char *filter_expression_copy = NULL;
+                       struct lttng_filter_bytecode *filter_copy = NULL;
 
-               kernel_wait_quiescent(kernel_tracer_fd);
-               break;
-       }
-       case LTTNG_DOMAIN_UST:
-       {
-               struct ltt_ust_channel *uchan;
-               struct ltt_ust_session *usess = session->ust_session;
+                       if (filter) {
+                               const size_t filter_size = sizeof(
+                                               struct lttng_filter_bytecode)
+                                               + filter->len;
 
-               assert(usess);
+                               filter_copy = zmalloc(filter_size);
+                               if (!filter_copy) {
+                                       ret = LTTNG_ERR_NOMEM;
+                                       goto error;
+                               }
+                               memcpy(filter_copy, filter, filter_size);
 
-               /* 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(domain);
-                       if (attr == NULL) {
-                               ret = LTTNG_ERR_FATAL;
-                               goto error;
-                       }
-                       strncpy(attr->name, channel_name, sizeof(attr->name));
+                               filter_expression_copy =
+                                               strdup(filter_expression);
+                               if (!filter_expression) {
+                                       ret = LTTNG_ERR_NOMEM;
+                               }
 
-                       ret = cmd_enable_channel(session, domain, attr, wpipe);
-                       if (ret != LTTNG_OK) {
-                               free(attr);
-                               goto error;
+                               if (!filter_expression_copy || !filter_copy) {
+                                       free(filter_expression_copy);
+                                       free(filter_copy);
+                                       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);
+                       ret = cmd_enable_event_internal(session, &tmp_dom,
+                                       (char *) default_chan_name,
+                                       &uevent, filter_expression_copy,
+                                       filter_copy, NULL, wpipe);
                }
 
-               /* 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, domain, uchan);
-                       if (ret != LTTNG_OK) {
-                               goto error;
-                       }
-                       break;
-               default:
-                       ret = LTTNG_ERR_UST_ENABLE_FAIL;
+               if (ret != LTTNG_OK && ret != LTTNG_ERR_UST_EVENT_ENABLED) {
                        goto error;
                }
 
-               /* Manage return value */
+               /* 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_expression);
+               } else {
+                       ret = event_agent_enable(usess, agt, event, filter,
+                                       filter_expression);
+               }
+               filter = NULL;
+               filter_expression = NULL;
                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;
@@ -1301,14 +1917,50 @@ int cmd_enable_event_all(struct ltt_session *session, int domain,
        ret = LTTNG_OK;
 
 error:
+       free(filter_expression);
+       free(filter);
+       free(exclusion);
+       rcu_read_unlock();
        return ret;
 }
 
+/*
+ * 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,
+               char *filter_expression,
+               struct lttng_filter_bytecode *filter,
+               struct lttng_event_exclusion *exclusion,
+               int wpipe)
+{
+       return _cmd_enable_event(session, domain, channel_name, event,
+                       filter_expression, filter, exclusion, wpipe, false);
+}
+
+/*
+ * Enable an event which is internal to LTTng. An internal should
+ * never be made visible to clients and are immune to checks such as
+ * reserved names.
+ */
+static int cmd_enable_event_internal(struct ltt_session *session,
+               struct lttng_domain *domain,
+               char *channel_name, struct lttng_event *event,
+               char *filter_expression,
+               struct lttng_filter_bytecode *filter,
+               struct lttng_event_exclusion *exclusion,
+               int wpipe)
+{
+       return _cmd_enable_event(session, domain, channel_name, event,
+                       filter_expression, filter, exclusion, wpipe, true);
+}
 
 /*
  * Command LTTNG_LIST_TRACEPOINTS processed by the client thread.
  */
-ssize_t cmd_list_tracepoints(int domain, struct lttng_event **events)
+ssize_t cmd_list_tracepoints(enum lttng_domain_type domain,
+               struct lttng_event **events)
 {
        int ret;
        ssize_t nb_events = 0;
@@ -1328,6 +1980,15 @@ ssize_t cmd_list_tracepoints(int domain, struct lttng_event **events)
                        goto error;
                }
                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;
+                       goto error;
+               }
+               break;
        default:
                ret = LTTNG_ERR_UND;
                goto error;
@@ -1343,7 +2004,7 @@ error:
 /*
  * Command LTTNG_LIST_TRACEPOINT_FIELDS processed by the client thread.
  */
-ssize_t cmd_list_tracepoint_fields(int domain,
+ssize_t cmd_list_tracepoint_fields(enum lttng_domain_type domain,
                struct lttng_event_field **fields)
 {
        int ret;
@@ -1370,15 +2031,73 @@ error:
        return -ret;
 }
 
+ssize_t cmd_list_syscalls(struct lttng_event **events)
+{
+       return syscall_table_list(events);
+}
+
+/*
+ * Command LTTNG_LIST_TRACKER_PIDS processed by the client thread.
+ *
+ * Called with session lock held.
+ */
+ssize_t cmd_list_tracker_pids(struct ltt_session *session,
+               enum lttng_domain_type domain, int32_t **pids)
+{
+       int ret;
+       ssize_t nr_pids = 0;
+
+       switch (domain) {
+       case LTTNG_DOMAIN_KERNEL:
+       {
+               struct ltt_kernel_session *ksess;
+
+               ksess = session->kernel_session;
+               nr_pids = kernel_list_tracker_pids(ksess, pids);
+               if (nr_pids < 0) {
+                       ret = LTTNG_ERR_KERN_LIST_FAIL;
+                       goto error;
+               }
+               break;
+       }
+       case LTTNG_DOMAIN_UST:
+       {
+               struct ltt_ust_session *usess;
+
+               usess = session->ust_session;
+               nr_pids = trace_ust_list_tracker_pids(usess, pids);
+               if (nr_pids < 0) {
+                       ret = LTTNG_ERR_UST_LIST_FAIL;
+                       goto error;
+               }
+               break;
+       }
+       case LTTNG_DOMAIN_LOG4J:
+       case LTTNG_DOMAIN_JUL:
+       case LTTNG_DOMAIN_PYTHON:
+       default:
+               ret = LTTNG_ERR_UND;
+               goto error;
+       }
+
+       return nr_pids;
+
+error:
+       /* Return negative value to differentiate return code */
+       return -ret;
+}
+
 /*
  * Command LTTNG_START_TRACE processed by the client thread.
+ *
+ * Called with session mutex held.
  */
 int cmd_start_trace(struct ltt_session *session)
 {
        int ret;
+       unsigned long nb_chan = 0;
        struct ltt_kernel_session *ksession;
        struct ltt_ust_session *usess;
-       struct ltt_kernel_channel *kchan;
 
        assert(session);
 
@@ -1386,75 +2105,42 @@ int cmd_start_trace(struct ltt_session *session)
        ksession = session->kernel_session;
        usess = session->ust_session;
 
-       if (session->enabled) {
-               /* Already started. */
+       /* Is the session already started? */
+       if (session->active) {
                ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
                goto error;
        }
 
-       session->enabled = 1;
-
-       ret = setup_relayd(session);
-       if (ret != LTTNG_OK) {
-               ERR("Error setting up relayd for session %s", session->name);
+       /*
+        * Starting a session without channel is useless since after that it's not
+        * possible to enable channel thus inform the client.
+        */
+       if (usess && usess->domain_global.channels) {
+               nb_chan += lttng_ht_get_count(usess->domain_global.channels);
+       }
+       if (ksession) {
+               nb_chan += ksession->channel_count;
+       }
+       if (!nb_chan) {
+               ret = LTTNG_ERR_NO_CHANNEL;
                goto error;
        }
 
        /* Kernel tracing */
        if (ksession != NULL) {
-               /* Open kernel metadata */
-               if (ksession->metadata == NULL) {
-                       ret = kernel_open_metadata(ksession);
-                       if (ret < 0) {
-                               ret = LTTNG_ERR_KERN_META_FAIL;
-                               goto error;
-                       }
-               }
-
-               /* Open kernel metadata stream */
-               if (ksession->metadata_stream_fd < 0) {
-                       ret = kernel_open_metadata_stream(ksession);
-                       if (ret < 0) {
-                               ERR("Kernel create metadata stream failed");
-                               ret = LTTNG_ERR_KERN_STREAM_FAIL;
-                               goto error;
-                       }
-               }
-
-               /* For each channel */
-               cds_list_for_each_entry(kchan, &ksession->channel_list.head, list) {
-                       if (kchan->stream_count == 0) {
-                               ret = kernel_open_channel_stream(kchan);
-                               if (ret < 0) {
-                                       ret = LTTNG_ERR_KERN_STREAM_FAIL;
-                                       goto error;
-                               }
-                               /* Update the stream global counter */
-                               ksession->stream_count_global += ret;
-                       }
-               }
-
-               /* Setup kernel consumer socket and send fds to it */
-               ret = init_kernel_tracing(ksession);
-               if (ret < 0) {
-                       ret = LTTNG_ERR_KERN_START_FAIL;
-                       goto error;
-               }
-
-               /* This start the kernel tracing */
-               ret = kernel_start_session(ksession);
-               if (ret < 0) {
-                       ret = LTTNG_ERR_KERN_START_FAIL;
+               ret = start_kernel_session(ksession, kernel_tracer_fd);
+               if (ret != LTTNG_OK) {
                        goto error;
                }
-
-               /* Quiescent wait after starting trace */
-               kernel_wait_quiescent(kernel_tracer_fd);
        }
 
        /* Flag session that trace should start automatically */
        if (usess) {
-               usess->start_trace = 1;
+               /*
+                * Even though the start trace might fail, flag this session active so
+                * other application coming in are started by default.
+                */
+               usess->active = 1;
 
                ret = ust_app_start_trace_all(usess);
                if (ret < 0) {
@@ -1463,6 +2149,10 @@ int cmd_start_trace(struct ltt_session *session)
                }
        }
 
+       /* Flag this after a successful start. */
+       session->has_been_started = 1;
+       session->active = 1;
+
        ret = LTTNG_OK;
 
 error:
@@ -1485,15 +2175,14 @@ int cmd_stop_trace(struct ltt_session *session)
        ksession = session->kernel_session;
        usess = session->ust_session;
 
-       if (!session->enabled) {
+       /* Session is not active. Skip everythong and inform the client. */
+       if (!session->active) {
                ret = LTTNG_ERR_TRACE_ALREADY_STOPPED;
                goto error;
        }
 
-       session->enabled = 0;
-
        /* Kernel tracer */
-       if (ksession) {
+       if (ksession && ksession->active) {
                DBG("Stop kernel tracing");
 
                /* Flush metadata if exist */
@@ -1519,10 +2208,16 @@ int cmd_stop_trace(struct ltt_session *session)
                }
 
                kernel_wait_quiescent(kernel_tracer_fd);
+
+               ksession->active = 0;
        }
 
-       if (usess) {
-               usess->start_trace = 0;
+       if (usess && usess->active) {
+               /*
+                * Even though the stop trace might fail, flag this session inactive so
+                * other application coming in are not started by default.
+                */
+               usess->active = 0;
 
                ret = ust_app_stop_trace_all(usess);
                if (ret < 0) {
@@ -1531,6 +2226,8 @@ int cmd_stop_trace(struct ltt_session *session)
                }
        }
 
+       /* Flag inactive after a successful stop. */
+       session->active = 0;
        ret = LTTNG_OK;
 
 error:
@@ -1540,115 +2237,69 @@ error:
 /*
  * Command LTTNG_SET_CONSUMER_URI processed by the client thread.
  */
-int cmd_set_consumer_uri(int domain, struct ltt_session *session,
-               size_t nb_uri, struct lttng_uri *uris)
+int cmd_set_consumer_uri(struct ltt_session *session, size_t nb_uri,
+               struct lttng_uri *uris)
 {
        int ret, i;
        struct ltt_kernel_session *ksess = session->kernel_session;
        struct ltt_ust_session *usess = session->ust_session;
-       struct consumer_output *consumer = NULL;
 
        assert(session);
        assert(uris);
        assert(nb_uri > 0);
 
-       /* Can't enable consumer after session started. */
-       if (session->enabled) {
+       /* Can't set consumer URI if the session is active. */
+       if (session->active) {
                ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
                goto error;
        }
 
-       /*
-        * This case switch makes sure the domain session has a temporary consumer
-        * so the URL can be set.
-        */
-       switch (domain) {
-       case 0:
-               /* Code flow error. A session MUST always have a consumer object */
-               assert(session->consumer);
-               /*
-                * The URL will be added to the tracing session consumer instead of a
-                * specific domain consumer.
-                */
-               consumer = session->consumer;
-               break;
-       case LTTNG_DOMAIN_KERNEL:
-               /* Code flow error if we don't have a kernel session here. */
-               assert(ksess);
-
-               /* Create consumer output if none exists */
-               consumer = ksess->tmp_consumer;
-               if (consumer == NULL) {
-                       consumer = consumer_copy_output(ksess->consumer);
-                       if (consumer == NULL) {
-                               ret = LTTNG_ERR_FATAL;
-                               goto error;
-                       }
-                       /* Trash the consumer subdir, we are about to set a new one. */
-                       memset(consumer->subdir, 0, sizeof(consumer->subdir));
-                       ksess->tmp_consumer = consumer;
+       /* Set the "global" consumer URIs */
+       for (i = 0; i < nb_uri; i++) {
+               ret = add_uri_to_consumer(session->consumer,
+                               &uris[i], 0, session->name);
+               if (ret != LTTNG_OK) {
+                       goto error;
                }
+       }
 
-               break;
-       case LTTNG_DOMAIN_UST:
-               /* Code flow error if we don't have a kernel session here. */
-               assert(usess);
-
-               /* Create consumer output if none exists */
-               consumer = usess->tmp_consumer;
-               if (consumer == NULL) {
-                       consumer = consumer_copy_output(usess->consumer);
-                       if (consumer == NULL) {
-                               ret = LTTNG_ERR_FATAL;
+       /* Set UST session URIs */
+       if (session->ust_session) {
+               for (i = 0; i < nb_uri; i++) {
+                       ret = add_uri_to_consumer(
+                                       session->ust_session->consumer,
+                                       &uris[i], LTTNG_DOMAIN_UST,
+                                       session->name);
+                       if (ret != LTTNG_OK) {
                                goto error;
                        }
-                       /* Trash the consumer subdir, we are about to set a new one. */
-                       memset(consumer->subdir, 0, sizeof(consumer->subdir));
-                       usess->tmp_consumer = consumer;
                }
-
-               break;
        }
 
-       for (i = 0; i < nb_uri; i++) {
-               struct consumer_socket *socket;
-               struct lttng_ht_iter iter;
-
-               ret = add_uri_to_consumer(consumer, &uris[i], domain, session->name);
-               if (ret < 0) {
-                       goto error;
-               }
-
-               /*
-                * Don't send relayd socket if URI is NOT remote or if the relayd
-                * socket for the session was already sent.
-                */
-               if (uris[i].dtype == LTTNG_DST_PATH ||
-                               (uris[i].stype == LTTNG_STREAM_CONTROL &&
-                               consumer->dst.net.control_sock_sent) ||
-                               (uris[i].stype == LTTNG_STREAM_DATA &&
-                               consumer->dst.net.data_sock_sent)) {
-                       continue;
-               }
-
-               /* Try to send relayd URI to the consumer if exist. */
-               rcu_read_lock();
-               cds_lfht_for_each_entry(consumer->socks->ht, &iter.iter,
-                               socket, node.node) {
-
-                       /* A socket in the HT should never have a negative fd */
-                       assert(socket->fd >= 0);
-
-                       pthread_mutex_lock(socket->lock);
-                       ret = send_consumer_relayd_socket(domain, session, &uris[i],
-                                       consumer, socket->fd);
-                       pthread_mutex_unlock(socket->lock);
+       /* Set kernel session URIs */
+       if (session->kernel_session) {
+               for (i = 0; i < nb_uri; i++) {
+                       ret = add_uri_to_consumer(
+                                       session->kernel_session->consumer,
+                                       &uris[i], LTTNG_DOMAIN_KERNEL,
+                                       session->name);
                        if (ret != LTTNG_OK) {
-                               rcu_read_unlock();
                                goto error;
                        }
                }
-               rcu_read_unlock();
+       }
+
+       /*
+        * Make sure to set the session in output mode after we set URI since a
+        * session can be created without URL (thus flagged in no output mode).
+        */
+       session->output_traces = 1;
+       if (ksess) {
+               ksess->output_traces = 1;
+       }
+
+       if (usess) {
+               usess->output_traces = 1;
        }
 
        /* All good! */
@@ -1662,13 +2313,13 @@ error:
  * Command LTTNG_CREATE_SESSION processed by the client thread.
  */
 int cmd_create_session_uri(char *name, struct lttng_uri *uris,
-               size_t nb_uri, lttng_sock_cred *creds)
+               size_t nb_uri, lttng_sock_cred *creds, unsigned int live_timer)
 {
        int ret;
-       char *path = NULL;
        struct ltt_session *session;
 
        assert(name);
+       assert(creds);
 
        /*
         * Verify if the session already exist
@@ -1684,7 +2335,7 @@ int cmd_create_session_uri(char *name, struct lttng_uri *uris,
        }
 
        /* Create tracing session in the registry */
-       ret = session_create(name, path, LTTNG_SOCK_GET_UID_CRED(creds),
+       ret = session_create(name, LTTNG_SOCK_GET_UID_CRED(creds),
                        LTTNG_SOCK_GET_GID_CRED(creds));
        if (ret != LTTNG_OK) {
                goto session_error;
@@ -1700,6 +2351,7 @@ int cmd_create_session_uri(char *name, struct lttng_uri *uris,
        session = session_find_by_name(name);
        assert(session);
 
+       session->live_timer = live_timer;
        /* Create default consumer output for the session not yet created. */
        session->consumer = consumer_create_output(CONSUMER_DST_LOCAL);
        if (session->consumer == NULL) {
@@ -1707,30 +2359,19 @@ int cmd_create_session_uri(char *name, struct lttng_uri *uris,
                goto consumer_error;
        }
 
-       /*
-        * This means that the lttng_create_session call was called with the _path_
-        * argument set to NULL.
-        */
-       if (uris == NULL) {
-               /*
-                * At this point, we'll skip the consumer URI setup and create a
-                * session with a NULL path which will flag the session to NOT spawn a
-                * consumer.
-                */
-               DBG("Create session %s with NO uri, skipping consumer setup", name);
-               goto end;
-       }
-
-       session->start_consumer = 1;
-
-       ret = cmd_set_consumer_uri(0, session, nb_uri, uris);
-       if (ret != LTTNG_OK) {
-               goto consumer_error;
+       if (uris) {
+               ret = cmd_set_consumer_uri(session, nb_uri, uris);
+               if (ret != LTTNG_OK) {
+                       goto consumer_error;
+               }
+               session->output_traces = 1;
+       } else {
+               session->output_traces = 0;
+               DBG2("Session %s created with no output", session->name);
        }
 
        session->consumer->enabled = 1;
 
-end:
        return LTTNG_OK;
 
 consumer_error:
@@ -1740,8 +2381,76 @@ find_error:
        return ret;
 }
 
+/*
+ * Command LTTNG_CREATE_SESSION_SNAPSHOT processed by the client thread.
+ */
+int cmd_create_session_snapshot(char *name, struct lttng_uri *uris,
+               size_t nb_uri, lttng_sock_cred *creds)
+{
+       int ret;
+       struct ltt_session *session;
+       struct snapshot_output *new_output = NULL;
+
+       assert(name);
+       assert(creds);
+
+       /*
+        * Create session in no output mode with URIs set to NULL. The uris we've
+        * received are for a default snapshot output if one.
+        */
+       ret = cmd_create_session_uri(name, NULL, 0, creds, 0);
+       if (ret != LTTNG_OK) {
+               goto error;
+       }
+
+       /* Get the newly created session pointer back. This should NEVER fail. */
+       session = session_find_by_name(name);
+       assert(session);
+
+       /* Flag session for snapshot mode. */
+       session->snapshot_mode = 1;
+
+       /* Skip snapshot output creation if no URI is given. */
+       if (nb_uri == 0) {
+               goto end;
+       }
+
+       new_output = snapshot_output_alloc();
+       if (!new_output) {
+               ret = LTTNG_ERR_NOMEM;
+               goto error_snapshot_alloc;
+       }
+
+       ret = snapshot_output_init_with_uri(DEFAULT_SNAPSHOT_MAX_SIZE, NULL,
+                       uris, nb_uri, session->consumer, new_output, &session->snapshot);
+       if (ret < 0) {
+               if (ret == -ENOMEM) {
+                       ret = LTTNG_ERR_NOMEM;
+               } else {
+                       ret = LTTNG_ERR_INVALID;
+               }
+               goto error_snapshot;
+       }
+
+       rcu_read_lock();
+       snapshot_add_output(&session->snapshot, new_output);
+       rcu_read_unlock();
+
+end:
+       return LTTNG_OK;
+
+error_snapshot:
+       snapshot_output_destroy(new_output);
+error_snapshot_alloc:
+       session_destroy(session);
+error:
+       return ret;
+}
+
 /*
  * Command LTTNG_DESTROY_SESSION processed by the client thread.
+ *
+ * Called with session lock held.
  */
 int cmd_destroy_session(struct ltt_session *session, int wpipe)
 {
@@ -1790,7 +2499,8 @@ int cmd_destroy_session(struct ltt_session *session, int wpipe)
 /*
  * Command LTTNG_CALIBRATE processed by the client thread.
  */
-int cmd_calibrate(int domain, struct lttng_calibrate *calibrate)
+int cmd_calibrate(enum lttng_domain_type domain,
+               struct lttng_calibrate *calibrate)
 {
        int ret;
 
@@ -1799,7 +2509,14 @@ int cmd_calibrate(int domain, struct lttng_calibrate *calibrate)
        {
                struct lttng_kernel_calibrate kcalibrate;
 
-               kcalibrate.type = calibrate->type;
+               switch (calibrate->type) {
+               case LTTNG_CALIBRATE_FUNCTION:
+               default:
+                       /* Default and only possible calibrate option. */
+                       kcalibrate.type = LTTNG_KERNEL_CALIBRATE_KRETPROBE;
+                       break;
+               }
+
                ret = kernel_calibrate(kernel_tracer_fd, &kcalibrate);
                if (ret < 0) {
                        ret = LTTNG_ERR_KERN_ENABLE_FAIL;
@@ -1811,7 +2528,14 @@ int cmd_calibrate(int domain, struct lttng_calibrate *calibrate)
        {
                struct lttng_ust_calibrate ucalibrate;
 
-               ucalibrate.type = calibrate->type;
+               switch (calibrate->type) {
+               case LTTNG_CALIBRATE_FUNCTION:
+               default:
+                       /* Default and only possible calibrate option. */
+                       ucalibrate.type = LTTNG_UST_CALIBRATE_TRACEPOINT;
+                       break;
+               }
+
                ret = ust_app_calibrate_glb(&ucalibrate);
                if (ret < 0) {
                        ret = LTTNG_ERR_UST_CALIBRATE_FAIL;
@@ -1833,11 +2557,12 @@ error:
 /*
  * Command LTTNG_REGISTER_CONSUMER processed by the client thread.
  */
-int cmd_register_consumer(struct ltt_session *session, int domain,
-               const char *sock_path, struct consumer_data *cdata)
+int cmd_register_consumer(struct ltt_session *session,
+               enum lttng_domain_type domain, const char *sock_path,
+               struct consumer_data *cdata)
 {
        int ret, sock;
-       struct consumer_socket *socket;
+       struct consumer_socket *socket = NULL;
 
        assert(session);
        assert(cdata);
@@ -1861,11 +2586,16 @@ int cmd_register_consumer(struct ltt_session *session, int domain,
                        ret = LTTNG_ERR_CONNECT_FAIL;
                        goto error;
                }
+               cdata->cmd_sock = sock;
 
-               socket = consumer_allocate_socket(sock);
+               socket = consumer_allocate_socket(&cdata->cmd_sock);
                if (socket == NULL) {
+                       ret = close(sock);
+                       if (ret < 0) {
+                               PERROR("close register consumer");
+                       }
+                       cdata->cmd_sock = -1;
                        ret = LTTNG_ERR_FATAL;
-                       close(sock);
                        goto error;
                }
 
@@ -1894,9 +2624,12 @@ int cmd_register_consumer(struct ltt_session *session, int domain,
                goto error;
        }
 
-       ret = LTTNG_OK;
+       return LTTNG_OK;
 
 error:
+       if (socket) {
+               consumer_destroy_socket(socket);
+       }
        return ret;
 }
 
@@ -1908,6 +2641,8 @@ ssize_t cmd_list_domains(struct ltt_session *session,
 {
        int ret, index = 0;
        ssize_t nb_dom = 0;
+       struct agent *agt;
+       struct lttng_ht_iter iter;
 
        if (session->kernel_session != NULL) {
                DBG3("Listing domains found kernel domain");
@@ -1917,6 +2652,19 @@ ssize_t cmd_list_domains(struct ltt_session *session,
        if (session->ust_session != NULL) {
                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));
@@ -1927,14 +2675,30 @@ ssize_t cmd_list_domains(struct ltt_session *session,
 
        if (session->kernel_session != NULL) {
                (*domains)[index].type = LTTNG_DOMAIN_KERNEL;
+
+               /* Kernel session buffer type is always GLOBAL */
+               (*domains)[index].buf_type = LTTNG_BUFFER_GLOBAL;
+
                index++;
        }
 
        if (session->ust_session != NULL) {
                (*domains)[index].type = LTTNG_DOMAIN_UST;
+               (*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) {
+                               (*domains)[index].type = agt->domain;
+                               (*domains)[index].buf_type = session->ust_session->buffer_type;
+                               index++;
+                       }
+               }
+               rcu_read_unlock();
+       }
+end:
        return nb_dom;
 
 error:
@@ -1946,8 +2710,8 @@ error:
 /*
  * Command LTTNG_LIST_CHANNELS processed by the client thread.
  */
-ssize_t cmd_list_channels(int domain, struct ltt_session *session,
-               struct lttng_channel **channels)
+ssize_t cmd_list_channels(enum lttng_domain_type domain,
+               struct ltt_session *session, struct lttng_channel **channels)
 {
        int ret;
        ssize_t nb_chan = 0;
@@ -1964,16 +2728,18 @@ 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;
        }
@@ -1986,10 +2752,6 @@ 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;
@@ -2002,8 +2764,9 @@ error:
 /*
  * Command LTTNG_LIST_EVENTS processed by the client thread.
  */
-ssize_t cmd_list_events(int domain, struct ltt_session *session,
-               char *channel_name, struct lttng_event **events)
+ssize_t cmd_list_events(enum lttng_domain_type domain,
+               struct ltt_session *session, char *channel_name,
+               struct lttng_event **events)
 {
        int ret = 0;
        ssize_t nb_event = 0;
@@ -2023,6 +2786,25 @@ ssize_t cmd_list_events(int domain, struct ltt_session *session,
                }
                break;
        }
+       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) {
+                               if (agt->domain == domain) {
+                                       nb_event = list_lttng_agent_events(
+                                                       agt, events);
+                                       break;
+                               }
+                       }
+                       rcu_read_unlock();
+               }
+               break;
        default:
                ret = LTTNG_ERR_UND;
                goto error;
@@ -2071,9 +2853,9 @@ void cmd_list_lttng_sessions(struct lttng_session *sessions, uid_t uid,
                                (ksess && ksess->consumer->type == CONSUMER_DST_NET) ||
                                (usess && usess->consumer->type == CONSUMER_DST_NET)) {
                        ret = build_network_session_path(sessions[i].path,
-                                       sizeof(session[i].path), session);
+                                       sizeof(sessions[i].path), session);
                } else {
-                       ret = snprintf(sessions[i].path, sizeof(session[i].path), "%s",
+                       ret = snprintf(sessions[i].path, sizeof(sessions[i].path), "%s",
                                        session->consumer->dst.trace_path);
                }
                if (ret < 0) {
@@ -2083,322 +2865,740 @@ void cmd_list_lttng_sessions(struct lttng_session *sessions, uid_t uid,
 
                strncpy(sessions[i].name, session->name, NAME_MAX);
                sessions[i].name[NAME_MAX - 1] = '\0';
-               sessions[i].enabled = session->enabled;
+               sessions[i].enabled = session->active;
+               sessions[i].snapshot_mode = session->snapshot_mode;
+               sessions[i].live_timer_interval = session->live_timer;
                i++;
        }
 }
 
 /*
- * Command LTTNG_DISABLE_CONSUMER processed by the client thread.
+ * Command LTTNG_DATA_PENDING returning 0 if the data is NOT pending meaning
+ * ready for trace analysis (or any kind of reader) or else 1 for pending data.
  */
-int cmd_disable_consumer(int domain, struct ltt_session *session)
+int cmd_data_pending(struct ltt_session *session)
 {
        int ret;
        struct ltt_kernel_session *ksess = session->kernel_session;
        struct ltt_ust_session *usess = session->ust_session;
-       struct consumer_output *consumer;
 
        assert(session);
 
-       if (session->enabled) {
-               /* Can't disable consumer on an already started session */
-               ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
+       /* Session MUST be stopped to ask for data availability. */
+       if (session->active) {
+               ret = LTTNG_ERR_SESSION_STARTED;
                goto error;
+       } else {
+               /*
+                * If stopped, just make sure we've started before else the above call
+                * will always send that there is data pending.
+                *
+                * The consumer assumes that when the data pending command is received,
+                * the trace has been started before or else no output data is written
+                * by the streams which is a condition for data pending. So, this is
+                * *VERY* important that we don't ask the consumer before a start
+                * trace.
+                */
+               if (!session->has_been_started) {
+                       ret = 0;
+                       goto error;
+               }
        }
 
-       if (!session->start_consumer) {
-               ret = LTTNG_ERR_NO_CONSUMER;
-               goto error;
+       if (ksess && ksess->consumer) {
+               ret = consumer_is_data_pending(ksess->id, ksess->consumer);
+               if (ret == 1) {
+                       /* Data is still being extracted for the kernel. */
+                       goto error;
+               }
        }
 
-       switch (domain) {
-       case 0:
-               DBG("Disable tracing session %s consumer", session->name);
-               consumer = session->consumer;
-               break;
-       case LTTNG_DOMAIN_KERNEL:
-               /* Code flow error if we don't have a kernel session here. */
-               assert(ksess);
+       if (usess && usess->consumer) {
+               ret = consumer_is_data_pending(usess->id, usess->consumer);
+               if (ret == 1) {
+                       /* Data is still being extracted for the kernel. */
+                       goto error;
+               }
+       }
+
+       /* Data is ready to be read by a viewer */
+       ret = 0;
 
-               DBG("Disabling kernel consumer");
-               consumer = ksess->consumer;
+error:
+       return ret;
+}
 
-               break;
-       case LTTNG_DOMAIN_UST:
-               /* Code flow error if we don't have a UST session here. */
-               assert(usess);
+/*
+ * Command LTTNG_SNAPSHOT_ADD_OUTPUT from the lttng ctl library.
+ *
+ * Return LTTNG_OK on success or else a LTTNG_ERR code.
+ */
+int cmd_snapshot_add_output(struct ltt_session *session,
+               struct lttng_snapshot_output *output, uint32_t *id)
+{
+       int ret;
+       struct snapshot_output *new_output;
 
-               DBG("Disabling UST consumer");
-               consumer = usess->consumer;
+       assert(session);
+       assert(output);
 
-               break;
-       default:
-               ret = LTTNG_ERR_UNKNOWN_DOMAIN;
+       DBG("Cmd snapshot add output for session %s", session->name);
+
+       /*
+        * Permission denied to create an output if the session is not
+        * set in no output mode.
+        */
+       if (session->output_traces) {
+               ret = LTTNG_ERR_EPERM;
                goto error;
        }
 
-       if (consumer) {
-               consumer->enabled = 0;
-               /* Success at this point */
-               ret = LTTNG_OK;
-       } else {
-               ret = LTTNG_ERR_NO_CONSUMER;
+       /* Only one output is allowed until we have the "tee" feature. */
+       if (session->snapshot.nb_output == 1) {
+               ret = LTTNG_ERR_SNAPSHOT_OUTPUT_EXIST;
+               goto error;
+       }
+
+       new_output = snapshot_output_alloc();
+       if (!new_output) {
+               ret = LTTNG_ERR_NOMEM;
+               goto error;
+       }
+
+       ret = snapshot_output_init(output->max_size, output->name,
+                       output->ctrl_url, output->data_url, session->consumer, new_output,
+                       &session->snapshot);
+       if (ret < 0) {
+               if (ret == -ENOMEM) {
+                       ret = LTTNG_ERR_NOMEM;
+               } else {
+                       ret = LTTNG_ERR_INVALID;
+               }
+               goto free_error;
        }
 
+       rcu_read_lock();
+       snapshot_add_output(&session->snapshot, new_output);
+       if (id) {
+               *id = new_output->id;
+       }
+       rcu_read_unlock();
+
+       return LTTNG_OK;
+
+free_error:
+       snapshot_output_destroy(new_output);
 error:
        return ret;
 }
 
 /*
- * Command LTTNG_ENABLE_CONSUMER processed by the client thread.
+ * Command LTTNG_SNAPSHOT_DEL_OUTPUT from lib lttng ctl.
+ *
+ * Return LTTNG_OK on success or else a LTTNG_ERR code.
  */
-int cmd_enable_consumer(int domain, struct ltt_session *session)
+int cmd_snapshot_del_output(struct ltt_session *session,
+               struct lttng_snapshot_output *output)
 {
        int ret;
-       struct ltt_kernel_session *ksess = session->kernel_session;
-       struct ltt_ust_session *usess = session->ust_session;
-       struct consumer_output *consumer = NULL;
+       struct snapshot_output *sout = NULL;
 
        assert(session);
+       assert(output);
 
-       /* Can't enable consumer after session started. */
-       if (session->enabled) {
-               ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
+       rcu_read_lock();
+
+       /*
+        * Permission denied to create an output if the session is not
+        * set in no output mode.
+        */
+       if (session->output_traces) {
+               ret = LTTNG_ERR_EPERM;
                goto error;
        }
 
-       switch (domain) {
-       case 0:
-               assert(session->consumer);
-               consumer = session->consumer;
-               break;
-       case LTTNG_DOMAIN_KERNEL:
-               /* Code flow error if we don't have a kernel session here. */
-               assert(ksess);
+       if (output->id) {
+               DBG("Cmd snapshot del output id %" PRIu32 " for session %s", output->id,
+                               session->name);
+               sout = snapshot_find_output_by_id(output->id, &session->snapshot);
+       } else if (*output->name != '\0') {
+               DBG("Cmd snapshot del output name %s for session %s", output->name,
+                               session->name);
+               sout = snapshot_find_output_by_name(output->name, &session->snapshot);
+       }
+       if (!sout) {
+               ret = LTTNG_ERR_INVALID;
+               goto error;
+       }
 
-               /*
-                * Check if we have already sent fds to the consumer. In that case,
-                * the enable-consumer command can't be used because a start trace
-                * had previously occured.
-                */
-               if (ksess->consumer_fds_sent) {
-                       ret = LTTNG_ERR_ENABLE_CONSUMER_FAIL;
-                       goto error;
-               }
+       snapshot_delete_output(&session->snapshot, sout);
+       snapshot_output_destroy(sout);
+       ret = LTTNG_OK;
 
-               consumer = ksess->tmp_consumer;
-               if (consumer == NULL) {
-                       ret = LTTNG_OK;
-                       /* No temp. consumer output exists. Using the current one. */
-                       DBG3("No temporary consumer. Using default");
-                       consumer = ksess->consumer;
-                       goto error;
-               }
+error:
+       rcu_read_unlock();
+       return ret;
+}
+
+/*
+ * Command LTTNG_SNAPSHOT_LIST_OUTPUT from lib lttng ctl.
+ *
+ * If no output is available, outputs is untouched and 0 is returned.
+ *
+ * Return the size of the newly allocated outputs or a negative LTTNG_ERR code.
+ */
+ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
+               struct lttng_snapshot_output **outputs)
+{
+       int ret, idx = 0;
+       struct lttng_snapshot_output *list = NULL;
+       struct lttng_ht_iter iter;
+       struct snapshot_output *output;
+
+       assert(session);
+       assert(outputs);
+
+       DBG("Cmd snapshot list outputs for session %s", session->name);
+
+       /*
+        * Permission denied to create an output if the session is not
+        * set in no output mode.
+        */
+       if (session->output_traces) {
+               ret = -LTTNG_ERR_EPERM;
+               goto error;
+       }
 
-               switch (consumer->type) {
-               case CONSUMER_DST_LOCAL:
-                       DBG2("Consumer output is local. Creating directory(ies)");
+       if (session->snapshot.nb_output == 0) {
+               ret = 0;
+               goto error;
+       }
+
+       list = zmalloc(session->snapshot.nb_output * sizeof(*list));
+       if (!list) {
+               ret = -LTTNG_ERR_NOMEM;
+               goto error;
+       }
 
-                       /* Create directory(ies) */
-                       ret = run_as_mkdir_recursive(consumer->dst.trace_path,
-                                       S_IRWXU | S_IRWXG, session->uid, session->gid);
+       /* 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);
+               list[idx].id = output->id;
+               list[idx].max_size = output->max_size;
+               strncpy(list[idx].name, output->name, sizeof(list[idx].name));
+               if (output->consumer->type == CONSUMER_DST_LOCAL) {
+                       strncpy(list[idx].ctrl_url, output->consumer->dst.trace_path,
+                                       sizeof(list[idx].ctrl_url));
+               } else {
+                       /* Control URI. */
+                       ret = uri_to_str_url(&output->consumer->dst.net.control,
+                                       list[idx].ctrl_url, sizeof(list[idx].ctrl_url));
                        if (ret < 0) {
-                               if (ret != -EEXIST) {
-                                       ERR("Trace directory creation error");
-                                       ret = LTTNG_ERR_FATAL;
-                                       goto error;
-                               }
-                       }
-                       break;
-               case CONSUMER_DST_NET:
-                       DBG2("Consumer output is network. Validating URIs");
-                       /* Validate if we have both control and data path set. */
-                       if (!consumer->dst.net.control_isset) {
-                               ret = LTTNG_ERR_URL_CTRL_MISS;
+                               ret = -LTTNG_ERR_NOMEM;
                                goto error;
                        }
 
-                       if (!consumer->dst.net.data_isset) {
-                               ret = LTTNG_ERR_URL_DATA_MISS;
+                       /* 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 error;
                        }
+               }
+               idx++;
+       }
 
-                       /* Check established network session state */
-                       if (session->net_handle == 0) {
-                               ret = LTTNG_ERR_ENABLE_CONSUMER_FAIL;
-                               ERR("Session network handle is not set on enable-consumer");
-                               goto error;
-                       }
+       *outputs = list;
+       list = NULL;
+       ret = session->snapshot.nb_output;
+error:
+       free(list);
+       rcu_read_unlock();
+       return ret;
+}
 
-                       break;
-               }
+/*
+ * Send relayd sockets from snapshot output to consumer. Ignore request if the
+ * snapshot output is *not* set with a remote destination.
+ *
+ * Return 0 on success or a LTTNG_ERR code.
+ */
+static int set_relayd_for_snapshot(struct consumer_output *consumer,
+               struct snapshot_output *snap_output, struct ltt_session *session)
+{
+       int ret = LTTNG_OK;
+       struct lttng_ht_iter iter;
+       struct consumer_socket *socket;
 
-               /*
-                * @session-lock
-                * This is race free for now since the session lock is acquired before
-                * ending up in this function. No other threads can access this kernel
-                * session without this lock hence freeing the consumer output object
-                * is valid.
-                */
-               rcu_read_lock();
-               /* Destroy current consumer. We are about to replace it */
-               consumer_destroy_output(ksess->consumer);
-               rcu_read_unlock();
-               ksess->consumer = consumer;
-               ksess->tmp_consumer = NULL;
+       assert(consumer);
+       assert(snap_output);
+       assert(session);
 
-               break;
-       case LTTNG_DOMAIN_UST:
-               /* Code flow error if we don't have a UST session here. */
-               assert(usess);
+       DBG2("Set relayd object from snapshot output");
 
-               /*
-                * Check if we have already sent fds to the consumer. In that case,
-                * the enable-consumer command can't be used because a start trace
-                * had previously occured.
-                */
-               if (usess->start_trace) {
-                       ret = LTTNG_ERR_ENABLE_CONSUMER_FAIL;
-                       goto error;
-               }
+       /* Ignore if snapshot consumer output is not network. */
+       if (snap_output->consumer->type != CONSUMER_DST_NET) {
+               goto error;
+       }
 
-               consumer = usess->tmp_consumer;
-               if (consumer == NULL) {
-                       ret = LTTNG_OK;
-                       /* No temp. consumer output exists. Using the current one. */
-                       DBG3("No temporary consumer. Using default");
-                       consumer = usess->consumer;
+       /*
+        * For each consumer socket, create and send the relayd object of the
+        * snapshot output.
+        */
+       rcu_read_lock();
+       cds_lfht_for_each_entry(snap_output->consumer->socks->ht, &iter.iter,
+                       socket, node.node) {
+               ret = send_consumer_relayd_sockets(0, session->id,
+                               snap_output->consumer, socket,
+                               session->name, session->hostname,
+                               session->live_timer);
+               if (ret != LTTNG_OK) {
+                       rcu_read_unlock();
                        goto error;
                }
+       }
+       rcu_read_unlock();
 
-               switch (consumer->type) {
-               case CONSUMER_DST_LOCAL:
-                       DBG2("Consumer output is local. Creating directory(ies)");
+error:
+       return ret;
+}
 
-                       /* Create directory(ies) */
-                       ret = run_as_mkdir_recursive(consumer->dst.trace_path,
-                                       S_IRWXU | S_IRWXG, session->uid, session->gid);
-                       if (ret < 0) {
-                               if (ret != -EEXIST) {
-                                       ERR("Trace directory creation error");
-                                       ret = LTTNG_ERR_FATAL;
-                                       goto error;
-                               }
-                       }
-                       break;
-               case CONSUMER_DST_NET:
-                       DBG2("Consumer output is network. Validating URIs");
-                       /* Validate if we have both control and data path set. */
-                       if (!consumer->dst.net.control_isset) {
-                               ret = LTTNG_ERR_URL_CTRL_MISS;
-                               goto error;
-                       }
+/*
+ * Record a kernel snapshot.
+ *
+ * Return LTTNG_OK on success or a LTTNG_ERR code.
+ */
+static int record_kernel_snapshot(struct ltt_kernel_session *ksess,
+               struct snapshot_output *output, struct ltt_session *session,
+               int wait, uint64_t nb_packets_per_stream)
+{
+       int ret;
 
-                       if (!consumer->dst.net.data_isset) {
-                               ret = LTTNG_ERR_URL_DATA_MISS;
-                               goto error;
-                       }
+       assert(ksess);
+       assert(output);
+       assert(session);
 
-                       /* Check established network session state */
-                       if (session->net_handle == 0) {
-                               ret = LTTNG_ERR_ENABLE_CONSUMER_FAIL;
-                               DBG2("Session network handle is not set on enable-consumer");
-                               goto error;
-                       }
+       /* Get the datetime for the snapshot output directory. */
+       ret = utils_get_current_time_str("%Y%m%d-%H%M%S", output->datetime,
+                       sizeof(output->datetime));
+       if (!ret) {
+               ret = LTTNG_ERR_INVALID;
+               goto error;
+       }
 
-                       if (consumer->net_seq_index == -1) {
-                               ret = LTTNG_ERR_ENABLE_CONSUMER_FAIL;
-                               DBG2("Network index is not set on the consumer");
-                               goto error;
-                       }
+       /*
+        * Copy kernel session sockets so we can communicate with the right
+        * consumer for the snapshot record command.
+        */
+       ret = consumer_copy_sockets(output->consumer, ksess->consumer);
+       if (ret < 0) {
+               ret = LTTNG_ERR_NOMEM;
+               goto error;
+       }
 
-                       break;
-               }
+       ret = set_relayd_for_snapshot(ksess->consumer, output, session);
+       if (ret != LTTNG_OK) {
+               goto error_snapshot;
+       }
 
-               /*
-                * @session-lock
-                * This is race free for now since the session lock is acquired before
-                * ending up in this function. No other threads can access this kernel
-                * session without this lock hence freeing the consumer output object
-                * is valid.
-                */
-               rcu_read_lock();
-               /* Destroy current consumer. We are about to replace it */
-               consumer_destroy_output(usess->consumer);
-               rcu_read_unlock();
-               usess->consumer = consumer;
-               usess->tmp_consumer = NULL;
+       ret = kernel_snapshot_record(ksess, output, wait, nb_packets_per_stream);
+       if (ret != LTTNG_OK) {
+               goto error_snapshot;
+       }
 
-               break;
+       ret = LTTNG_OK;
+       goto end;
+
+error_snapshot:
+       /* Clean up copied sockets so this output can use some other later on. */
+       consumer_destroy_output_sockets(output->consumer);
+error:
+end:
+       return ret;
+}
+
+/*
+ * Record a UST snapshot.
+ *
+ * Return 0 on success or a LTTNG_ERR error code.
+ */
+static int record_ust_snapshot(struct ltt_ust_session *usess,
+               struct snapshot_output *output, struct ltt_session *session,
+               int wait, uint64_t nb_packets_per_stream)
+{
+       int ret;
+
+       assert(usess);
+       assert(output);
+       assert(session);
+
+       /* Get the datetime for the snapshot output directory. */
+       ret = utils_get_current_time_str("%Y%m%d-%H%M%S", output->datetime,
+                       sizeof(output->datetime));
+       if (!ret) {
+               ret = LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       /*
+        * Copy UST session sockets so we can communicate with the right
+        * consumer for the snapshot record command.
+        */
+       ret = consumer_copy_sockets(output->consumer, usess->consumer);
+       if (ret < 0) {
+               ret = LTTNG_ERR_NOMEM;
+               goto error;
        }
 
-       session->start_consumer = 1;
+       ret = set_relayd_for_snapshot(usess->consumer, output, session);
+       if (ret != LTTNG_OK) {
+               goto error_snapshot;
+       }
 
-       /* Enable it */
-       if (consumer) {
-               consumer->enabled = 1;
-               /* Success at this point */
-               ret = LTTNG_OK;
-       } else {
-               /* Should not really happend... */
-               ret = LTTNG_ERR_NO_CONSUMER;
+       ret = ust_app_snapshot_record(usess, output, wait, nb_packets_per_stream);
+       if (ret < 0) {
+               switch (-ret) {
+               case EINVAL:
+                       ret = LTTNG_ERR_INVALID;
+                       break;
+               case ENODATA:
+                       ret = LTTNG_ERR_SNAPSHOT_NODATA;
+                       break;
+               default:
+                       ret = LTTNG_ERR_SNAPSHOT_FAIL;
+                       break;
+               }
+               goto error_snapshot;
        }
 
+       ret = LTTNG_OK;
+
+error_snapshot:
+       /* Clean up copied sockets so this output can use some other later on. */
+       consumer_destroy_output_sockets(output->consumer);
 error:
        return ret;
 }
 
+static
+uint64_t get_session_size_one_more_packet_per_stream(struct ltt_session *session,
+       uint64_t cur_nr_packets)
+{
+       uint64_t tot_size = 0;
+
+       if (session->kernel_session) {
+               struct ltt_kernel_channel *chan;
+               struct ltt_kernel_session *ksess = session->kernel_session;
+
+               cds_list_for_each_entry(chan, &ksess->channel_list.head, list) {
+                       if (cur_nr_packets >= chan->channel->attr.num_subbuf) {
+                               /*
+                                * Don't take channel into account if we
+                                * already grab all its packets.
+                                */
+                               continue;
+                       }
+                       tot_size += chan->channel->attr.subbuf_size
+                               * chan->stream_count;
+               }
+       }
+
+       if (session->ust_session) {
+               struct ltt_ust_session *usess = session->ust_session;
+
+               tot_size += ust_app_get_size_one_more_packet_per_stream(usess,
+                               cur_nr_packets);
+       }
+
+       return tot_size;
+}
+
 /*
- * Command LTTNG_DATA_PENDING returning 0 if the data is NOT pending meaning
- * ready for trace analysis (or anykind of reader) or else 1 for pending data.
+ * Calculate the number of packets we can grab from each stream that
+ * fits within the overall snapshot max size.
+ *
+ * Returns -1 on error, 0 means infinite number of packets, else > 0 is
+ * the number of packets per stream.
+ *
+ * TODO: this approach is not perfect: we consider the worse case
+ * (packet filling the sub-buffers) as an upper bound, but we could do
+ * better if we do this calculation while we actually grab the packet
+ * content: we would know how much padding we don't actually store into
+ * the file.
+ *
+ * This algorithm is currently bounded by the number of packets per
+ * stream.
+ *
+ * Since we call this algorithm before actually grabbing the data, it's
+ * an approximation: for instance, applications could appear/disappear
+ * in between this call and actually grabbing data.
  */
-int cmd_data_pending(struct ltt_session *session)
+static
+int64_t get_session_nb_packets_per_stream(struct ltt_session *session, uint64_t max_size)
 {
-       int ret;
-       struct ltt_kernel_session *ksess = session->kernel_session;
-       struct ltt_ust_session *usess = session->ust_session;
+       int64_t size_left;
+       uint64_t cur_nb_packets = 0;
+
+       if (!max_size) {
+               return 0;       /* Infinite */
+       }
+
+       size_left = max_size;
+       for (;;) {
+               uint64_t one_more_packet_tot_size;
+
+               one_more_packet_tot_size = get_session_size_one_more_packet_per_stream(session,
+                                       cur_nb_packets);
+               if (!one_more_packet_tot_size) {
+                       /* We are already grabbing all packets. */
+                       break;
+               }
+               size_left -= one_more_packet_tot_size;
+               if (size_left < 0) {
+                       break;
+               }
+               cur_nb_packets++;
+       }
+       if (!cur_nb_packets) {
+               /* Not enough room to grab one packet of each stream, error. */
+               return -1;
+       }
+       return cur_nb_packets;
+}
+
+/*
+ * Command LTTNG_SNAPSHOT_RECORD from lib lttng ctl.
+ *
+ * The wait parameter is ignored so this call always wait for the snapshot to
+ * complete before returning.
+ *
+ * Return LTTNG_OK on success or else a LTTNG_ERR code.
+ */
+int cmd_snapshot_record(struct ltt_session *session,
+               struct lttng_snapshot_output *output, int wait)
+{
+       int ret = LTTNG_OK;
+       unsigned int use_tmp_output = 0;
+       struct snapshot_output tmp_output;
+       unsigned int snapshot_success = 0;
 
        assert(session);
+       assert(output);
 
-       /* Session MUST be stopped to ask for data availability. */
-       if (session->enabled) {
-               ret = LTTNG_ERR_SESSION_STARTED;
+       DBG("Cmd snapshot record for session %s", session->name);
+
+       /*
+        * Permission denied to create an output if the session is not
+        * set in no output mode.
+        */
+       if (session->output_traces) {
+               ret = LTTNG_ERR_EPERM;
                goto error;
        }
 
-       if (ksess && ksess->consumer) {
-               ret = consumer_is_data_pending(ksess->id, ksess->consumer);
-               if (ret == 1) {
-                       /* Data is still being extracted for the kernel. */
+       /* The session needs to be started at least once. */
+       if (!session->has_been_started) {
+               ret = LTTNG_ERR_START_SESSION_ONCE;
+               goto error;
+       }
+
+       /* Use temporary output for the session. */
+       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);
+               if (ret < 0) {
+                       if (ret == -ENOMEM) {
+                               ret = LTTNG_ERR_NOMEM;
+                       } else {
+                               ret = LTTNG_ERR_INVALID;
+                       }
                        goto error;
                }
+               /* Use the global session count for the temporary snapshot. */
+               tmp_output.nb_snapshot = session->snapshot.nb_snapshot;
+               use_tmp_output = 1;
        }
 
-       if (usess && usess->consumer) {
-               ret = consumer_is_data_pending(usess->id, usess->consumer);
-               if (ret == 1) {
-                       /* Data is still being extracted for the kernel. */
-                       goto error;
+       if (session->kernel_session) {
+               struct ltt_kernel_session *ksess = session->kernel_session;
+
+               if (use_tmp_output) {
+                       int64_t nb_packets_per_stream;
+
+                       nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+                                       tmp_output.max_size);
+                       if (nb_packets_per_stream < 0) {
+                               ret = LTTNG_ERR_MAX_SIZE_INVALID;
+                               goto error;
+                       }
+                       ret = record_kernel_snapshot(ksess, &tmp_output, session,
+                                       wait, nb_packets_per_stream);
+                       if (ret != LTTNG_OK) {
+                               goto error;
+                       }
+                       snapshot_success = 1;
+               } else {
+                       struct snapshot_output *sout;
+                       struct lttng_ht_iter iter;
+
+                       rcu_read_lock();
+                       cds_lfht_for_each_entry(session->snapshot.output_ht->ht,
+                                       &iter.iter, sout, node.node) {
+                               int64_t nb_packets_per_stream;
+
+                               /*
+                                * Make a local copy of the output and assign the possible
+                                * temporary value given by the caller.
+                                */
+                               memset(&tmp_output, 0, sizeof(tmp_output));
+                               memcpy(&tmp_output, sout, sizeof(tmp_output));
+
+                               if (output->max_size != (uint64_t) -1ULL) {
+                                       tmp_output.max_size = output->max_size;
+                               }
+
+                               nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+                                               tmp_output.max_size);
+                               if (nb_packets_per_stream < 0) {
+                                       ret = LTTNG_ERR_MAX_SIZE_INVALID;
+                                       goto error;
+                               }
+
+                               /* Use temporary name. */
+                               if (*output->name != '\0') {
+                                       strncpy(tmp_output.name, output->name,
+                                                       sizeof(tmp_output.name));
+                               }
+
+                               tmp_output.nb_snapshot = session->snapshot.nb_snapshot;
+
+                               ret = record_kernel_snapshot(ksess, &tmp_output,
+                                               session, wait, nb_packets_per_stream);
+                               if (ret != LTTNG_OK) {
+                                       rcu_read_unlock();
+                                       goto error;
+                               }
+                               snapshot_success = 1;
+                       }
+                       rcu_read_unlock();
                }
        }
 
-       /* Data is ready to be read by a viewer */
-       ret = 0;
+       if (session->ust_session) {
+               struct ltt_ust_session *usess = session->ust_session;
+
+               if (use_tmp_output) {
+                       int64_t nb_packets_per_stream;
+
+                       nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+                                       tmp_output.max_size);
+                       if (nb_packets_per_stream < 0) {
+                               ret = LTTNG_ERR_MAX_SIZE_INVALID;
+                               goto error;
+                       }
+                       ret = record_ust_snapshot(usess, &tmp_output, session,
+                                       wait, nb_packets_per_stream);
+                       if (ret != LTTNG_OK) {
+                               goto error;
+                       }
+                       snapshot_success = 1;
+               } else {
+                       struct snapshot_output *sout;
+                       struct lttng_ht_iter iter;
+
+                       rcu_read_lock();
+                       cds_lfht_for_each_entry(session->snapshot.output_ht->ht,
+                                       &iter.iter, sout, node.node) {
+                               int64_t nb_packets_per_stream;
+
+                               /*
+                                * Make a local copy of the output and assign the possible
+                                * temporary value given by the caller.
+                                */
+                               memset(&tmp_output, 0, sizeof(tmp_output));
+                               memcpy(&tmp_output, sout, sizeof(tmp_output));
+
+                               if (output->max_size != (uint64_t) -1ULL) {
+                                       tmp_output.max_size = output->max_size;
+                               }
+
+                               nb_packets_per_stream = get_session_nb_packets_per_stream(session,
+                                               tmp_output.max_size);
+                               if (nb_packets_per_stream < 0) {
+                                       ret = LTTNG_ERR_MAX_SIZE_INVALID;
+                                       rcu_read_unlock();
+                                       goto error;
+                               }
+
+                               /* Use temporary name. */
+                               if (*output->name != '\0') {
+                                       strncpy(tmp_output.name, output->name,
+                                                       sizeof(tmp_output.name));
+                               }
+
+                               tmp_output.nb_snapshot = session->snapshot.nb_snapshot;
+
+                               ret = record_ust_snapshot(usess, &tmp_output, session,
+                                               wait, nb_packets_per_stream);
+                               if (ret != LTTNG_OK) {
+                                       rcu_read_unlock();
+                                       goto error;
+                               }
+                               snapshot_success = 1;
+                       }
+                       rcu_read_unlock();
+               }
+       }
+
+       if (snapshot_success) {
+               session->snapshot.nb_snapshot++;
+       } else {
+               ret = LTTNG_ERR_SNAPSHOT_FAIL;
+       }
 
 error:
        return ret;
 }
 
+/*
+ * Command LTTNG_SET_SESSION_SHM_PATH processed by the client thread.
+ */
+int cmd_set_session_shm_path(struct ltt_session *session,
+               const char *shm_path)
+{
+       /* Safety net */
+       assert(session);
+
+       /*
+        * Can only set shm path before session is started.
+        */
+       if (session->has_been_started) {
+               return LTTNG_ERR_SESSION_STARTED;
+       }
+
+       strncpy(session->shm_path, shm_path,
+               sizeof(session->shm_path));
+       session->shm_path[sizeof(session->shm_path) - 1] = '\0';
+
+       return 0;
+}
+
 /*
  * Init command subsystem.
  */
 void cmd_init(void)
 {
        /*
-        * Set network sequence index to 1 for streams to match a relayd socket on
-        * the consumer side.
+        * Set network sequence index to 1 for streams to match a relayd
+        * socket on the consumer side.
         */
-       uatomic_set(&relayd_net_seq_idx, 1);
+       pthread_mutex_lock(&relayd_net_seq_idx_lock);
+       relayd_net_seq_idx = 1;
+       pthread_mutex_unlock(&relayd_net_seq_idx_lock);
 
        DBG("Command subsystem initialized");
 }
This page took 0.096632 seconds and 4 git commands to generate.