Docs: add comment to cmd_add_context()
[lttng-tools.git] / src / bin / lttng-sessiond / cmd.c
index 812c850faa73b9b4efb34b5030c6f46dd22c00d2..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
@@ -15,7 +16,7 @@
  * 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>
@@ -26,6 +27,7 @@
 #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"
@@ -35,6 +37,8 @@
 #include "kernel-consumer.h"
 #include "lttng-sessiond.h"
 #include "utils.h"
+#include "syscall.h"
+#include "agent.h"
 
 #include "cmd.h"
 
 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
  * session consumer is on the network.
@@ -128,8 +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;
@@ -166,6 +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:
@@ -183,25 +199,27 @@ static void list_lttng_channels(int domain, struct ltt_session *session,
 }
 
 /*
- * Create a list of JUL domain events.
+ * Create a list of agent domain events.
  *
  * Return number of events in list on success or else a negative value.
  */
-static int list_lttng_jul_events(struct jul_domain *dom,
+static int list_lttng_agent_events(struct agent *agt,
                struct lttng_event **events)
 {
        int i = 0, ret = 0;
        unsigned int nb_event = 0;
-       struct jul_event *event;
+       struct agent_event *event;
        struct lttng_event *tmp_events;
        struct lttng_ht_iter iter;
 
-       assert(dom);
+       assert(agt);
        assert(events);
 
-       DBG3("Listing JUL events");
+       DBG3("Listing agent events");
 
-       nb_event = lttng_ht_get_count(dom->events);
+       rcu_read_lock();
+       nb_event = lttng_ht_get_count(agt->events);
+       rcu_read_unlock();
        if (nb_event == 0) {
                ret = nb_event;
                goto error;
@@ -209,16 +227,18 @@ static int list_lttng_jul_events(struct jul_domain *dom,
 
        tmp_events = zmalloc(nb_event * sizeof(*tmp_events));
        if (!tmp_events) {
-               PERROR("zmalloc JUL events session");
+               PERROR("zmalloc agent events session");
                ret = -LTTNG_ERR_FATAL;
                goto error;
        }
 
        rcu_read_lock();
-       cds_lfht_for_each_entry(dom->events->ht, &iter.iter, event, node.node) {
+       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();
@@ -258,8 +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;
@@ -274,6 +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;
@@ -341,7 +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));
@@ -355,6 +380,8 @@ 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:
@@ -388,7 +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:
@@ -401,7 +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;
@@ -458,6 +498,7 @@ static int add_uri_to_consumer(struct consumer_output *consumer,
                         * 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;
                }
 
@@ -597,8 +638,9 @@ error:
 /*
  * Connect to the relayd using URI and send the socket to the right consumer.
  */
-static int send_consumer_relayd_socket(int domain, unsigned int session_id,
-               struct lttng_uri *relayd_uri, struct consumer_output *consumer,
+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)
 {
@@ -668,9 +710,10 @@ error:
  * helper function to facilitate sending the information to the consumer for a
  * session.
  */
-static int send_consumer_relayd_sockets(int domain, unsigned int session_id,
-               struct consumer_output *consumer, struct consumer_socket *sock,
-               char *session_name, char *hostname, int session_live_timer)
+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;
 
@@ -822,7 +865,7 @@ static int start_kernel_session(struct ltt_kernel_session *ksess, int wpipe)
        /* Quiescent wait after starting trace */
        kernel_wait_quiescent(kernel_tracer_fd);
 
-       ksess->started = 1;
+       ksess->active = 1;
 
        ret = LTTNG_OK;
 
@@ -833,8 +876,8 @@ 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;
@@ -874,11 +917,108 @@ int cmd_disable_channel(struct ltt_session *session, int domain,
                }
                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_TRACK_PID processed by the client thread.
+ *
+ * Called with session lock held.
+ */
+int cmd_track_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_session *ksess;
+
+               ksess = session->kernel_session;
+
+               ret = kernel_track_pid(ksess, pid);
+               if (ret != LTTNG_OK) {
+                       goto error;
+               }
+
+               kernel_wait_quiescent(kernel_tracer_fd);
+               break;
+       }
+       case LTTNG_DOMAIN_UST:
+       {
+               struct ltt_ust_session *usess;
+
+               usess = session->ust_session;
+
+               ret = trace_ust_track_pid(usess, pid);
+               if (ret != LTTNG_OK) {
+                       goto error;
+               }
+               break;
+       }
+       default:
+               ret = LTTNG_ERR_UNKNOWN_DOMAIN;
+               goto error;
+       }
+
+       ret = LTTNG_OK;
+
+error:
+       rcu_read_unlock();
+       return ret;
+}
+
+/*
+ * Command LTTNG_UNTRACK_PID processed by the client thread.
+ *
+ * Called with session lock held.
+ */
+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_session *ksess;
+
+               ksess = session->kernel_session;
+
+               ret = kernel_untrack_pid(ksess, pid);
+               if (ret != LTTNG_OK) {
+                       goto error;
+               }
+
+               kernel_wait_quiescent(kernel_tracer_fd);
+               break;
+       }
+       case LTTNG_DOMAIN_UST:
+       {
+               struct ltt_ust_session *usess;
+
+               usess = session->ust_session;
+
+               ret = trace_ust_untrack_pid(usess, pid);
+               if (ret != LTTNG_OK) {
+                       goto error;
+               }
+               break;
+       }
        default:
                ret = LTTNG_ERR_UNKNOWN_DOMAIN;
                goto error;
@@ -902,11 +1042,21 @@ int cmd_enable_channel(struct ltt_session *session,
        int ret;
        struct ltt_ust_session *usess = session->ust_session;
        struct lttng_ht *chan_ht;
+       size_t len;
 
        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();
@@ -915,7 +1065,7 @@ int cmd_enable_channel(struct ltt_session *session,
         * 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->started) {
+       if (session->has_been_started) {
                ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
                goto error;
        }
@@ -930,6 +1080,16 @@ int cmd_enable_channel(struct ltt_session *session,
                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:
        {
@@ -938,15 +1098,6 @@ int cmd_enable_channel(struct ltt_session *session,
                kchan = trace_kernel_get_channel_by_name(attr->name,
                                session->kernel_session);
                if (kchan == NULL) {
-                       /*
-                        * Don't try to create a channel if the session
-                        * has been started at some point in time
-                        * before. The tracer does not allow it.
-                        */
-                       if (session->started) {
-                               ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
-                               goto error;
-                       }
                        ret = channel_kernel_create(session->kernel_session, attr, wpipe);
                        if (attr->name[0] != '\0') {
                                session->kernel_session->has_non_default_channel = 1;
@@ -963,22 +1114,44 @@ int cmd_enable_channel(struct ltt_session *session,
                break;
        }
        case LTTNG_DOMAIN_UST:
+       case LTTNG_DOMAIN_JUL:
+       case LTTNG_DOMAIN_LOG4J:
+       case LTTNG_DOMAIN_PYTHON:
        {
                struct ltt_ust_channel *uchan;
 
+               /*
+                * 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) {
-                       /*
-                        * Don't try to create a channel if the session
-                        * has been started at some point in time
-                        * before. The tracer does not allow it.
-                        */
-                       if (session->started) {
-                               ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
-                               goto error;
-                       }
                        ret = channel_ust_create(usess, attr, domain->buf_type);
                        if (attr->name[0] != '\0') {
                                usess->has_non_default_channel = 1;
@@ -995,17 +1168,34 @@ int cmd_enable_channel(struct ltt_session *session,
 
 error:
        rcu_read_unlock();
+end:
        return ret;
 }
 
-
 /*
  * Command LTTNG_DISABLE_EVENT processed by the client thread.
  */
-int cmd_disable_event(struct ltt_session *session, int domain,
-               char *channel_name, char *event_name)
+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();
 
@@ -1024,18 +1214,36 @@ int cmd_disable_event(struct ltt_session *session, int domain,
                 */
                if (ksess->has_non_default_channel && channel_name[0] == '\0') {
                        ret = LTTNG_ERR_NEED_CHANNEL_NAME;
-                       goto error;
+                       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;
+                       goto error_unlock;
                }
 
-               ret = event_kernel_disable_tracepoint(kchan, event_name);
-               if (ret != LTTNG_OK) {
-                       goto error;
+               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);
@@ -1048,174 +1256,116 @@ int cmd_disable_event(struct ltt_session *session, int domain,
 
                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, explicitely require that -c chan_name needs
+                * 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;
+                       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_tracepoint(usess, uchan, event_name);
-               if (ret != LTTNG_OK) {
-                       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);
 
-               ret = event_jul_disable(usess, event_name);
-               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;
-
-error:
-       rcu_read_unlock();
-       return ret;
-}
-
-/*
- * Command LTTNG_DISABLE_ALL_EVENT processed by the client thread.
- */
-int cmd_disable_event_all(struct ltt_session *session, int domain,
-               char *channel_name)
-{
-       int ret;
-
-       rcu_read_lock();
-
-       switch (domain) {
-       case LTTNG_DOMAIN_KERNEL:
-       {
-               struct ltt_kernel_session *ksess;
-               struct ltt_kernel_channel *kchan;
-
-               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;
-               }
-
-               kchan = trace_kernel_get_channel_by_name(channel_name, ksess);
-               if (kchan == NULL) {
-                       ret = LTTNG_ERR_KERN_CHAN_NOT_FOUND;
-                       goto error;
+               switch (event->type) {
+               case LTTNG_EVENT_ALL:
+                       break;
+               default:
+                       ret = LTTNG_ERR_UNK;
+                       goto error_unlock;
                }
 
-               ret = event_kernel_disable_all(kchan);
-               if (ret != LTTNG_OK) {
-                       goto error;
+               agt = trace_ust_find_agent(usess, domain);
+               if (!agt) {
+                       ret = -LTTNG_ERR_UST_EVENT_NOT_FOUND;
+                       goto error_unlock;
                }
-
-               kernel_wait_quiescent(kernel_tracer_fd);
-               break;
-       }
-       case LTTNG_DOMAIN_UST:
-       {
-               struct ltt_ust_session *usess;
-               struct ltt_ust_channel *uchan;
-
-               usess = session->ust_session;
-
                /*
-                * If a non-default channel has been created in the
-                * session, explicitely require that -c chan_name needs
-                * to be provided.
+                * An empty event name means that everything
+                * should be disabled.
                 */
-               if (usess->has_non_default_channel && channel_name[0] == '\0') {
-                       ret = LTTNG_ERR_NEED_CHANNEL_NAME;
-                       goto error;
-               }
-
-               uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
-                               channel_name);
-               if (uchan == NULL) {
-                       ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
-                       goto error;
-               }
-
-               ret = event_ust_disable_all_tracepoints(usess, uchan);
-               if (ret != 0) {
-                       goto error;
+               if (event->name[0] == '\0') {
+                       ret = event_agent_disable_all(usess, agt);
+               } else {
+                       ret = event_agent_disable(usess, agt, event_name);
                }
-
-               DBG3("Disable all UST events in channel %s completed", channel_name);
-
-               break;
-       }
-       case LTTNG_DOMAIN_JUL:
-       {
-               struct ltt_ust_session *usess = session->ust_session;
-
-               assert(usess);
-
-               ret = event_jul_disable_all(usess);
                if (ret != LTTNG_OK) {
-                       goto error;
+                       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:
+error_unlock:
        rcu_read_unlock();
+error:
        return ret;
 }
 
 /*
  * Command LTTNG_ADD_CONTEXT processed by the client thread.
  */
-int cmd_add_context(struct ltt_session *session, int domain,
+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, 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:
@@ -1235,6 +1385,29 @@ int cmd_add_context(struct ltt_session *session, int domain,
                        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;
@@ -1262,22 +1435,22 @@ int cmd_add_context(struct ltt_session *session, int domain,
                }
 
                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;
        }
 
-       return LTTNG_OK;
+       ret = LTTNG_OK;
+       goto end;
 
 error:
        if (chan_kern_created) {
@@ -1301,17 +1474,93 @@ error:
                                uchan);
                trace_ust_destroy_channel(uchan);
        }
+end:
+       free(app_ctx_provider_name);
+       free(app_ctx_name);
+       return ret;
+}
+
+static int validate_event_name(const char *name)
+{
+       int ret = 0;
+       const char *c = name;
+       const char *event_name_end = c + LTTNG_SYMBOL_NAME_LEN;
+       bool null_terminated = false;
+
+       /*
+        * 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;
+               }
+               c++;
+       }
+end:
+       if (!ret && !null_terminated) {
+               ret = LTTNG_ERR_INVALID_EVENT_NAME;
+       }
+       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, struct lttng_domain *domain,
+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)
+               int wpipe, bool internal_event)
 {
        int ret, channel_created = 0;
        struct lttng_channel *attr;
@@ -1320,8 +1569,18 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
        assert(event);
        assert(channel_name);
 
+       /* 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:
        {
@@ -1368,216 +1627,88 @@ int cmd_enable_event(struct ltt_session *session, struct lttng_domain *domain,
                        goto error;
                }
 
-               ret = event_kernel_enable_tracepoint(kchan, event);
-               if (ret != LTTNG_OK) {
-                       if (channel_created) {
-                               /* Let's not leak a useless channel. */
-                               kernel_destroy_channel(kchan);
-                       }
-                       goto error;
-               }
-
-               kernel_wait_quiescent(kernel_tracer_fd);
-               break;
-       }
-       case LTTNG_DOMAIN_UST:
-       {
-               struct ltt_ust_channel *uchan;
-               struct ltt_ust_session *usess = session->ust_session;
-
-               assert(usess);
-
-               /*
-                * If a non-default channel has been created in the
-                * session, explicitely require that -c chan_name needs
-                * to be provided.
-                */
-               if (usess->has_non_default_channel && channel_name[0] == '\0') {
-                       ret = LTTNG_ERR_NEED_CHANNEL_NAME;
-                       goto error;
-               }
+               switch (event->type) {
+               case LTTNG_EVENT_ALL:
+               {
+                       char *filter_expression_a = NULL;
+                       struct lttng_filter_bytecode *filter_a = NULL;
 
-               /* Get channel from global UST domain */
-               uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
-                               channel_name);
-               if (uchan == NULL) {
-                       /* Create default channel */
-                       attr = channel_new_default_attr(LTTNG_DOMAIN_UST,
-                                       usess->buffer_type);
-                       if (attr == NULL) {
-                               ret = LTTNG_ERR_FATAL;
+                       /*
+                        * 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;
                        }
-                       strncpy(attr->name, channel_name, sizeof(attr->name));
-
-                       ret = cmd_enable_channel(session, domain, attr, wpipe);
+                       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) {
-                               free(attr);
                                goto error;
                        }
-                       free(attr);
-
-                       /* Get the newly created channel reference back */
-                       uchan = trace_ust_find_channel_by_name(
-                                       usess->domain_global.channels, channel_name);
-                       assert(uchan);
-               }
-
-               /* At this point, the session and channel exist on the tracer */
-               ret = event_ust_enable_tracepoint(usess, uchan, event, filter, exclusion);
-               if (ret != LTTNG_OK) {
-                       goto error;
-               }
-               break;
-       }
-       case LTTNG_DOMAIN_JUL:
-       {
-               struct lttng_event uevent;
-               struct lttng_domain tmp_dom;
-               struct ltt_ust_session *usess = session->ust_session;
-
-               assert(usess);
-
-               /* Create the default JUL tracepoint. */
-               memset(&uevent, 0, sizeof(uevent));
-               uevent.type = LTTNG_EVENT_TRACEPOINT;
-               uevent.loglevel_type = LTTNG_EVENT_LOGLEVEL_ALL;
-               if (is_root) {
-                       strncpy(uevent.name, DEFAULT_SYS_JUL_EVENT_NAME,
-                                       sizeof(uevent.name));
-               } else {
-                       strncpy(uevent.name, DEFAULT_USER_JUL_EVENT_NAME,
-                                       sizeof(uevent.name));
-               }
-               uevent.name[sizeof(uevent.name) - 1] = '\0';
-
-               /*
-                * 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;
-
-               ret = cmd_enable_event(session, &tmp_dom, DEFAULT_JUL_CHANNEL_NAME,
-                               &uevent, NULL, NULL, wpipe);
-               if (ret != LTTNG_OK && ret != LTTNG_ERR_UST_EVENT_ENABLED) {
-                       goto error;
-               }
-
-               /* The wild card * means that everything should be enabled. */
-               if (strncmp(event->name, "*", 1) == 0 && strlen(event->name) == 1) {
-                       ret = event_jul_enable_all(usess, event);
-               } else {
-                       ret = event_jul_enable(usess, event);
-               }
-               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;
-
-error:
-       rcu_read_unlock();
-       return ret;
-}
-
-/*
- * Command LTTNG_ENABLE_ALL_EVENT processed by the client thread.
- */
-int cmd_enable_event_all(struct ltt_session *session,
-               struct lttng_domain *domain, char *channel_name, int event_type,
-               struct lttng_filter_bytecode *filter, int wpipe)
-{
-       int ret;
-       struct lttng_channel *attr;
-
-       assert(session);
-       assert(channel_name);
-
-       rcu_read_lock();
-
-       switch (domain->type) {
-       case LTTNG_DOMAIN_KERNEL:
-       {
-               struct ltt_kernel_channel *kchan;
-
-               assert(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 (session->kernel_session->has_non_default_channel
-                               && channel_name[0] == '\0') {
-                       ret = LTTNG_ERR_NEED_CHANNEL_NAME;
-                       goto error;
+                       break;
                }
-
-               kchan = trace_kernel_get_channel_by_name(channel_name,
-                               session->kernel_session);
-               if (kchan == NULL) {
-                       /* Create default channel */
-                       attr = channel_new_default_attr(LTTNG_DOMAIN_KERNEL,
-                                       LTTNG_BUFFER_GLOBAL);
-                       if (attr == NULL) {
-                               ret = LTTNG_ERR_FATAL;
+               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;
                        }
-                       strncpy(attr->name, channel_name, sizeof(attr->name));
-
-                       ret = cmd_enable_channel(session, domain, attr, wpipe);
+                       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) {
-                               free(attr);
                                goto error;
                        }
-                       free(attr);
-
-                       /* Get the newly created kernel channel pointer */
-                       kchan = trace_kernel_get_channel_by_name(channel_name,
-                                       session->kernel_session);
-                       assert(kchan);
-               }
-
-               switch (event_type) {
-               case LTTNG_EVENT_SYSCALL:
-                       ret = event_kernel_enable_all_syscalls(kchan, kernel_tracer_fd);
-                       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(kchan, kernel_tracer_fd);
-                       break;
-               case LTTNG_EVENT_ALL:
-                       /* Enable syscalls and tracepoints */
-                       ret = event_kernel_enable_all(kchan, kernel_tracer_fd);
                        break;
                default:
-                       ret = LTTNG_ERR_KERN_ENABLE_FAIL;
-                       goto error;
-               }
-
-               /* Manage return value */
-               if (ret != LTTNG_OK) {
-                       /*
-                        * On error, cmd_enable_channel call will take care of destroying
-                        * the created channel if it was needed.
-                        */
+                       ret = LTTNG_ERR_UNK;
                        goto error;
                }
 
@@ -1627,46 +1758,77 @@ int cmd_enable_event_all(struct ltt_session *session,
                        assert(uchan);
                }
 
-               /* At this point, the session and channel exist on the tracer */
+               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;
+               }
 
-               switch (event_type) {
-               case LTTNG_EVENT_ALL:
-               case LTTNG_EVENT_TRACEPOINT:
-                       ret = event_ust_enable_all_tracepoints(usess, uchan, filter);
-                       if (ret != LTTNG_OK) {
+               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;
                        }
-                       break;
-               default:
-                       ret = LTTNG_ERR_UST_ENABLE_FAIL;
-                       goto error;
                }
 
-               /* Manage return value */
-               if (ret != LTTNG_OK) {
+               /* At this point, the session and channel exist on the tracer */
+               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;
        }
+       case LTTNG_DOMAIN_LOG4J:
        case LTTNG_DOMAIN_JUL:
+       case LTTNG_DOMAIN_PYTHON:
        {
-               struct lttng_event uevent, event;
+               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;
 
                assert(usess);
 
-               /* Create the default JUL tracepoint. */
+               agt = trace_ust_find_agent(usess, domain->type);
+               if (!agt) {
+                       agt = agent_create(domain->type);
+                       if (!agt) {
+                               ret = LTTNG_ERR_NOMEM;
+                               goto error;
+                       }
+                       agent_add(agt, usess->agents);
+               }
+
+               /* Create the default tracepoint. */
+               memset(&uevent, 0, sizeof(uevent));
                uevent.type = LTTNG_EVENT_TRACEPOINT;
                uevent.loglevel_type = LTTNG_EVENT_LOGLEVEL_ALL;
-               if (is_root) {
-                       strncpy(uevent.name, DEFAULT_SYS_JUL_EVENT_NAME,
-                                       sizeof(uevent.name));
-               } else {
-                       strncpy(uevent.name, DEFAULT_USER_JUL_EVENT_NAME,
-                                       sizeof(uevent.name));
+               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';
 
                /*
@@ -1677,29 +1839,76 @@ int cmd_enable_event_all(struct ltt_session *session,
                memcpy(&tmp_dom, domain, sizeof(tmp_dom));
                tmp_dom.type = LTTNG_DOMAIN_UST;
 
-               ret = cmd_enable_event(session, &tmp_dom, DEFAULT_JUL_CHANNEL_NAME,
-                               &uevent, NULL, NULL, wpipe);
+               switch (domain->type) {
+               case LTTNG_DOMAIN_LOG4J:
+                       default_chan_name = DEFAULT_LOG4J_CHANNEL_NAME;
+                       break;
+               case LTTNG_DOMAIN_JUL:
+                       default_chan_name = DEFAULT_JUL_CHANNEL_NAME;
+                       break;
+               case LTTNG_DOMAIN_PYTHON:
+                       default_chan_name = DEFAULT_PYTHON_CHANNEL_NAME;
+                       break;
+               default:
+                       /* The switch/case we are in makes this impossible */
+                       assert(0);
+               }
+
+               {
+                       char *filter_expression_copy = NULL;
+                       struct lttng_filter_bytecode *filter_copy = NULL;
+
+                       if (filter) {
+                               const size_t filter_size = sizeof(
+                                               struct lttng_filter_bytecode)
+                                               + filter->len;
+
+                               filter_copy = zmalloc(filter_size);
+                               if (!filter_copy) {
+                                       ret = LTTNG_ERR_NOMEM;
+                                       goto error;
+                               }
+                               memcpy(filter_copy, filter, filter_size);
+
+                               filter_expression_copy =
+                                               strdup(filter_expression);
+                               if (!filter_expression) {
+                                       ret = LTTNG_ERR_NOMEM;
+                               }
+
+                               if (!filter_expression_copy || !filter_copy) {
+                                       free(filter_expression_copy);
+                                       free(filter_copy);
+                                       goto error;
+                               }
+                       }
+
+                       ret = cmd_enable_event_internal(session, &tmp_dom,
+                                       (char *) default_chan_name,
+                                       &uevent, filter_expression_copy,
+                                       filter_copy, NULL, wpipe);
+               }
+
                if (ret != LTTNG_OK && ret != LTTNG_ERR_UST_EVENT_ENABLED) {
                        goto error;
                }
 
-               event.loglevel = LTTNG_LOGLEVEL_JUL_ALL;
-               event.loglevel_type = LTTNG_EVENT_LOGLEVEL_ALL;
-               strncpy(event.name, "*", sizeof(event.name));
-               event.name[sizeof(event.name) - 1] = '\0';
-
-               ret = event_jul_enable_all(usess, &event);
+               /* 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;
@@ -1708,15 +1917,50 @@ int cmd_enable_event_all(struct ltt_session *session,
        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;
@@ -1736,8 +1980,10 @@ ssize_t cmd_list_tracepoints(int domain, struct lttng_event **events)
                        goto error;
                }
                break;
+       case LTTNG_DOMAIN_LOG4J:
        case LTTNG_DOMAIN_JUL:
-               nb_events = jul_list_events(events);
+       case LTTNG_DOMAIN_PYTHON:
+               nb_events = agent_list_events(events, domain);
                if (nb_events < 0) {
                        ret = LTTNG_ERR_UST_LIST_FAIL;
                        goto error;
@@ -1758,7 +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;
@@ -1785,8 +2031,66 @@ 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)
 {
@@ -1801,8 +2105,8 @@ 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;
        }
@@ -1822,8 +2126,6 @@ int cmd_start_trace(struct ltt_session *session)
                goto error;
        }
 
-       session->enabled = 1;
-
        /* Kernel tracing */
        if (ksession != NULL) {
                ret = start_kernel_session(ksession, kernel_tracer_fd);
@@ -1834,7 +2136,11 @@ int cmd_start_trace(struct ltt_session *session)
 
        /* 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) {
@@ -1843,7 +2149,9 @@ int cmd_start_trace(struct ltt_session *session)
                }
        }
 
-       session->started = 1;
+       /* Flag this after a successful start. */
+       session->has_been_started = 1;
+       session->active = 1;
 
        ret = LTTNG_OK;
 
@@ -1867,15 +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 && ksession->started) {
+       if (ksession && ksession->active) {
                DBG("Stop kernel tracing");
 
                /* Flush metadata if exist */
@@ -1902,11 +2209,15 @@ int cmd_stop_trace(struct ltt_session *session)
 
                kernel_wait_quiescent(kernel_tracer_fd);
 
-               ksession->started = 0;
+               ksession->active = 0;
        }
 
-       if (usess && usess->start_trace) {
-               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) {
@@ -1915,6 +2226,8 @@ int cmd_stop_trace(struct ltt_session *session)
                }
        }
 
+       /* Flag inactive after a successful stop. */
+       session->active = 0;
        ret = LTTNG_OK;
 
 error:
@@ -1924,59 +2237,71 @@ 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);
-               assert(ksess->consumer);
-               consumer = ksess->consumer;
-               break;
-       case LTTNG_DOMAIN_UST:
-               /* Code flow error if we don't have a kernel session here. */
-               assert(usess);
-               assert(usess->consumer);
-               consumer = usess->consumer;
-               break;
-       }
-
+       /* Set the "global" consumer URIs */
        for (i = 0; i < nb_uri; i++) {
-               ret = add_uri_to_consumer(consumer, &uris[i], domain, session->name);
+               ret = add_uri_to_consumer(session->consumer,
+                               &uris[i], 0, session->name);
                if (ret != LTTNG_OK) {
                        goto error;
                }
        }
 
+       /* 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;
+                       }
+               }
+       }
+
+       /* 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) {
+                               goto error;
+                       }
+               }
+       }
+
+       /*
+        * 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! */
        ret = LTTNG_OK;
 
@@ -2035,7 +2360,7 @@ int cmd_create_session_uri(char *name, struct lttng_uri *uris,
        }
 
        if (uris) {
-               ret = cmd_set_consumer_uri(0, session, nb_uri, uris);
+               ret = cmd_set_consumer_uri(session, nb_uri, uris);
                if (ret != LTTNG_OK) {
                        goto consumer_error;
                }
@@ -2073,7 +2398,7 @@ int cmd_create_session_snapshot(char *name, struct lttng_uri *uris,
         * 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, -1);
+       ret = cmd_create_session_uri(name, NULL, 0, creds, 0);
        if (ret != LTTNG_OK) {
                goto error;
        }
@@ -2124,6 +2449,8 @@ error:
 
 /*
  * Command LTTNG_DESTROY_SESSION processed by the client thread.
+ *
+ * Called with session lock held.
  */
 int cmd_destroy_session(struct ltt_session *session, int wpipe)
 {
@@ -2172,7 +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;
 
@@ -2229,8 +2557,9 @@ 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 = NULL;
@@ -2312,6 +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");
@@ -2322,9 +2653,18 @@ ssize_t cmd_list_domains(struct ltt_session *session,
                DBG3("Listing domains found UST global domain");
                nb_dom++;
 
-               if (session->ust_session->domain_jul.being_used) {
-                       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));
@@ -2335,6 +2675,10 @@ 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++;
        }
 
@@ -2343,13 +2687,18 @@ ssize_t cmd_list_domains(struct ltt_session *session,
                (*domains)[index].buf_type = session->ust_session->buffer_type;
                index++;
 
-               if (session->ust_session->domain_jul.being_used) {
-                       (*domains)[index].type = LTTNG_DOMAIN_JUL;
-                       (*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:
@@ -2361,8 +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;
@@ -2379,16 +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;
        }
@@ -2401,10 +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;
@@ -2417,8 +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;
@@ -2438,10 +2786,23 @@ 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) {
-                       nb_event = list_lttng_jul_events(
-                                       &session->ust_session->domain_jul, events);
+                       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:
@@ -2504,7 +2865,7 @@ 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++;
@@ -2524,9 +2885,24 @@ int cmd_data_pending(struct ltt_session *session)
        assert(session);
 
        /* Session MUST be stopped to ask for data availability. */
-       if (session->enabled) {
+       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 (ksess && ksess->consumer) {
@@ -2675,7 +3051,7 @@ ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
                struct lttng_snapshot_output **outputs)
 {
        int ret, idx = 0;
-       struct lttng_snapshot_output *list;
+       struct lttng_snapshot_output *list = NULL;
        struct lttng_ht_iter iter;
        struct snapshot_output *output;
 
@@ -2689,7 +3065,7 @@ ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
         * set in no output mode.
         */
        if (session->output_traces) {
-               ret = LTTNG_ERR_EPERM;
+               ret = -LTTNG_ERR_EPERM;
                goto error;
        }
 
@@ -2700,11 +3076,12 @@ ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
 
        list = zmalloc(session->snapshot.nb_output * sizeof(*list));
        if (!list) {
-               ret = LTTNG_ERR_NOMEM;
+               ret = -LTTNG_ERR_NOMEM;
                goto error;
        }
 
        /* Copy list from session to the new list object. */
+       rcu_read_lock();
        cds_lfht_for_each_entry(session->snapshot.output_ht->ht, &iter.iter,
                        output, node.node) {
                assert(output->consumer);
@@ -2719,28 +3096,28 @@ ssize_t cmd_snapshot_list_outputs(struct ltt_session *session,
                        ret = uri_to_str_url(&output->consumer->dst.net.control,
                                        list[idx].ctrl_url, sizeof(list[idx].ctrl_url));
                        if (ret < 0) {
-                               ret = LTTNG_ERR_NOMEM;
-                               goto free_error;
+                               ret = -LTTNG_ERR_NOMEM;
+                               goto error;
                        }
 
                        /* Data URI. */
                        ret = uri_to_str_url(&output->consumer->dst.net.data,
                                        list[idx].data_url, sizeof(list[idx].data_url));
                        if (ret < 0) {
-                               ret = LTTNG_ERR_NOMEM;
-                               goto free_error;
+                               ret = -LTTNG_ERR_NOMEM;
+                               goto error;
                        }
                }
                idx++;
        }
 
        *outputs = list;
-       return session->snapshot.nb_output;
-
-free_error:
-       free(list);
+       list = NULL;
+       ret = session->snapshot.nb_output;
 error:
-       return -ret;
+       free(list);
+       rcu_read_unlock();
+       return ret;
 }
 
 /*
@@ -2796,7 +3173,7 @@ error:
  */
 static int record_kernel_snapshot(struct ltt_kernel_session *ksess,
                struct snapshot_output *output, struct ltt_session *session,
-               int wait, int nb_streams)
+               int wait, uint64_t nb_packets_per_stream)
 {
        int ret;
 
@@ -2827,17 +3204,19 @@ static int record_kernel_snapshot(struct ltt_kernel_session *ksess,
                goto error_snapshot;
        }
 
-       ret = kernel_snapshot_record(ksess, output, wait, nb_streams);
+       ret = kernel_snapshot_record(ksess, output, wait, nb_packets_per_stream);
        if (ret != LTTNG_OK) {
                goto error_snapshot;
        }
 
        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;
 }
 
@@ -2848,7 +3227,7 @@ error:
  */
 static int record_ust_snapshot(struct ltt_ust_session *usess,
                struct snapshot_output *output, struct ltt_session *session,
-               int wait, int nb_streams)
+               int wait, uint64_t nb_packets_per_stream)
 {
        int ret;
 
@@ -2879,7 +3258,7 @@ static int record_ust_snapshot(struct ltt_ust_session *usess,
                goto error_snapshot;
        }
 
-       ret = ust_app_snapshot_record(usess, output, wait, nb_streams);
+       ret = ust_app_snapshot_record(usess, output, wait, nb_packets_per_stream);
        if (ret < 0) {
                switch (-ret) {
                case EINVAL:
@@ -2904,27 +3283,90 @@ error:
        return ret;
 }
 
-/*
- * Returns the total number of streams for a session or a negative value
- * on error.
- */
-static unsigned int get_total_nb_stream(struct ltt_session *session)
+static
+uint64_t get_session_size_one_more_packet_per_stream(struct ltt_session *session,
+       uint64_t cur_nr_packets)
 {
-       unsigned int total_streams = 0;
+       uint64_t tot_size = 0;
 
        if (session->kernel_session) {
+               struct ltt_kernel_channel *chan;
                struct ltt_kernel_session *ksess = session->kernel_session;
 
-               total_streams += ksess->stream_count_global;
+               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;
 
-               total_streams += ust_app_get_nb_stream(usess);
+               tot_size += ust_app_get_size_one_more_packet_per_stream(usess,
+                               cur_nr_packets);
+       }
+
+       return tot_size;
+}
+
+/*
+ * 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.
+ */
+static
+int64_t get_session_nb_packets_per_stream(struct ltt_session *session, uint64_t max_size)
+{
+       int64_t size_left;
+       uint64_t cur_nb_packets = 0;
+
+       if (!max_size) {
+               return 0;       /* Infinite */
        }
 
-       return total_streams;
+       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;
 }
 
 /*
@@ -2941,9 +3383,10 @@ int cmd_snapshot_record(struct ltt_session *session,
        int ret = LTTNG_OK;
        unsigned int use_tmp_output = 0;
        struct snapshot_output tmp_output;
-       unsigned int nb_streams, snapshot_success = 0;
+       unsigned int snapshot_success = 0;
 
        assert(session);
+       assert(output);
 
        DBG("Cmd snapshot record for session %s", session->name);
 
@@ -2957,13 +3400,13 @@ int cmd_snapshot_record(struct ltt_session *session,
        }
 
        /* The session needs to be started at least once. */
-       if (!session->started) {
+       if (!session->has_been_started) {
                ret = LTTNG_ERR_START_SESSION_ONCE;
                goto error;
        }
 
        /* Use temporary output for the session. */
-       if (output && *output->ctrl_url != '\0') {
+       if (*output->ctrl_url != '\0') {
                ret = snapshot_output_init(output->max_size, output->name,
                                output->ctrl_url, output->data_url, session->consumer,
                                &tmp_output, NULL);
@@ -2980,18 +3423,20 @@ int cmd_snapshot_record(struct ltt_session *session,
                use_tmp_output = 1;
        }
 
-       /*
-        * Get the total number of stream of that session which is used by the
-        * maximum size of the snapshot feature.
-        */
-       nb_streams = get_total_nb_stream(session);
-
        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_streams);
+                                       wait, nb_packets_per_stream);
                        if (ret != LTTNG_OK) {
                                goto error;
                        }
@@ -3003,6 +3448,8 @@ int cmd_snapshot_record(struct ltt_session *session,
                        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.
@@ -3010,11 +3457,17 @@ int cmd_snapshot_record(struct ltt_session *session,
                                memset(&tmp_output, 0, sizeof(tmp_output));
                                memcpy(&tmp_output, sout, sizeof(tmp_output));
 
-                               /* Use temporary max size. */
                                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,
@@ -3024,7 +3477,7 @@ int cmd_snapshot_record(struct ltt_session *session,
                                tmp_output.nb_snapshot = session->snapshot.nb_snapshot;
 
                                ret = record_kernel_snapshot(ksess, &tmp_output,
-                                               session, wait, nb_streams);
+                                               session, wait, nb_packets_per_stream);
                                if (ret != LTTNG_OK) {
                                        rcu_read_unlock();
                                        goto error;
@@ -3039,8 +3492,16 @@ int cmd_snapshot_record(struct ltt_session *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_streams);
+                                       wait, nb_packets_per_stream);
                        if (ret != LTTNG_OK) {
                                goto error;
                        }
@@ -3052,6 +3513,8 @@ int cmd_snapshot_record(struct ltt_session *session,
                        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.
@@ -3059,11 +3522,18 @@ int cmd_snapshot_record(struct ltt_session *session,
                                memset(&tmp_output, 0, sizeof(tmp_output));
                                memcpy(&tmp_output, sout, sizeof(tmp_output));
 
-                               /* Use temporary max size. */
                                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,
@@ -3073,7 +3543,7 @@ int cmd_snapshot_record(struct ltt_session *session,
                                tmp_output.nb_snapshot = session->snapshot.nb_snapshot;
 
                                ret = record_ust_snapshot(usess, &tmp_output, session,
-                                               wait, nb_streams);
+                                               wait, nb_packets_per_stream);
                                if (ret != LTTNG_OK) {
                                        rcu_read_unlock();
                                        goto error;
@@ -3094,6 +3564,29 @@ 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.
  */
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