Fix: split UST per UID/PID default values
[lttng-tools.git] / src / bin / lttng-sessiond / ust-app.c
index 225d3f86a81a3837b4acbf9ed23c5d3cf01a9416..5710226fc4504cb609eefa0b31ac4c989e15276a 100644 (file)
@@ -17,6 +17,7 @@
 
 #define _GNU_SOURCE
 #include <errno.h>
+#include <inttypes.h>
 #include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <urcu/compiler.h>
 #include <lttng/ust-error.h>
+#include <signal.h>
 
 #include <common/common.h>
 #include <common/sessiond-comm/sessiond-comm.h>
 
+#include "buffer-registry.h"
 #include "fd-limit.h"
 #include "health.h"
 #include "ust-app.h"
@@ -38,6 +41,7 @@
 
 /* Next available channel key. */
 static unsigned long next_channel_key;
+static unsigned long next_session_id;
 
 /*
  * Return the atomically incremented value of next_channel_key.
@@ -48,38 +52,24 @@ static inline unsigned long get_next_channel_key(void)
 }
 
 /*
- * Return the consumer socket from the given consumer output with the right
- * bitness. On error, returns NULL.
- *
- * The caller MUST acquire a rcu read side lock and keep it until the socket
- * object reference is not needed anymore.
+ * Return the atomically incremented value of next_session_id.
  */
-static struct consumer_socket *find_consumer_socket_by_bitness(int bits,
-               struct consumer_output *consumer)
+static inline unsigned long get_next_session_id(void)
 {
-       int consumer_fd;
-       struct consumer_socket *socket = NULL;
-
-       switch (bits) {
-       case 64:
-               consumer_fd = uatomic_read(&ust_consumerd64_fd);
-               break;
-       case 32:
-               consumer_fd = uatomic_read(&ust_consumerd32_fd);
-               break;
-       default:
-               assert(0);
-               goto end;
-       }
-
-       socket = consumer_find_socket(consumer_fd, consumer);
-       if (!socket) {
-               ERR("Consumer socket fd %d not found in consumer obj %p",
-                               consumer_fd, consumer);
-       }
+       return uatomic_add_return(&next_session_id, 1);
+}
 
-end:
-       return socket;
+static void copy_channel_attr_to_ustctl(
+               struct ustctl_consumer_channel_attr *attr,
+               struct lttng_ust_channel_attr *uattr)
+{
+       /* Copy event attributes since the layout is different. */
+       attr->subbuf_size = uattr->subbuf_size;
+       attr->num_subbuf = uattr->num_subbuf;
+       attr->overwrite = uattr->overwrite;
+       attr->switch_timer_interval = uattr->switch_timer_interval;
+       attr->read_timer_interval = uattr->read_timer_interval;
+       attr->output = uattr->output;
 }
 
 /*
@@ -190,6 +180,48 @@ static void close_notify_sock_rcu(struct rcu_head *head)
        free(obj);
 }
 
+/*
+ * Return the session registry according to the buffer type of the given
+ * session.
+ *
+ * A registry per UID object MUST exists before calling this function or else
+ * it assert() if not found. RCU read side lock must be acquired.
+ */
+static struct ust_registry_session *get_session_registry(
+               struct ust_app_session *ua_sess)
+{
+       struct ust_registry_session *registry = NULL;
+
+       assert(ua_sess);
+
+       switch (ua_sess->buffer_type) {
+       case LTTNG_BUFFER_PER_PID:
+       {
+               struct buffer_reg_pid *reg_pid = buffer_reg_pid_find(ua_sess->id);
+               if (!reg_pid) {
+                       goto error;
+               }
+               registry = reg_pid->registry->reg.ust;
+               break;
+       }
+       case LTTNG_BUFFER_PER_UID:
+       {
+               struct buffer_reg_uid *reg_uid = buffer_reg_uid_find(
+                               ua_sess->tracing_id, ua_sess->bits_per_long, ua_sess->uid);
+               if (!reg_uid) {
+                       goto error;
+               }
+               registry = reg_uid->registry->reg.ust;
+               break;
+       }
+       default:
+               assert(0);
+       };
+
+error:
+       return registry;
+}
+
 /*
  * Delete ust context safely. RCU read lock must be held before calling
  * this function.
@@ -237,13 +269,13 @@ void delete_ust_app_event(int sock, struct ust_app_event *ua_event)
 }
 
 /*
- * Delete ust app stream safely. RCU read lock must be held before calling
- * this function.
+ * Release ust data object of the given stream.
+ *
+ * Return 0 on success or else a negative value.
  */
-static
-void delete_ust_app_stream(int sock, struct ust_app_stream *stream)
+static int release_ust_app_stream(int sock, struct ust_app_stream *stream)
 {
-       int ret;
+       int ret = 0;
 
        assert(stream);
 
@@ -256,9 +288,40 @@ void delete_ust_app_stream(int sock, struct ust_app_stream *stream)
                lttng_fd_put(LTTNG_FD_APPS, 2);
                free(stream->obj);
        }
+
+       return ret;
+}
+
+/*
+ * Delete ust app stream safely. RCU read lock must be held before calling
+ * this function.
+ */
+static
+void delete_ust_app_stream(int sock, struct ust_app_stream *stream)
+{
+       assert(stream);
+
+       (void) release_ust_app_stream(sock, stream);
        free(stream);
 }
 
+/*
+ * We need to execute ht_destroy outside of RCU read-side critical
+ * section, so we postpone its execution using call_rcu. It is simpler
+ * than to change the semantic of the many callers of
+ * delete_ust_app_channel().
+ */
+static
+void delete_ust_app_channel_rcu(struct rcu_head *head)
+{
+       struct ust_app_channel *ua_chan =
+               caa_container_of(head, struct ust_app_channel, rcu_head);
+
+       lttng_ht_destroy(ua_chan->ctx);
+       lttng_ht_destroy(ua_chan->events);
+       free(ua_chan);
+}
+
 /*
  * Delete ust app channel safely. RCU read lock must be held before calling
  * this function.
@@ -272,6 +335,7 @@ void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan,
        struct ust_app_event *ua_event;
        struct ust_app_ctx *ua_ctx;
        struct ust_app_stream *stream, *stmp;
+       struct ust_registry_session *registry;
 
        assert(ua_chan);
 
@@ -289,7 +353,6 @@ void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan,
                assert(!ret);
                delete_ust_app_ctx(sock, ua_ctx);
        }
-       lttng_ht_destroy(ua_chan->ctx);
 
        /* Wipe events */
        cds_lfht_for_each_entry(ua_chan->events->ht, &iter.iter, ua_event,
@@ -298,10 +361,12 @@ void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan,
                assert(!ret);
                delete_ust_app_event(sock, ua_event);
        }
-       lttng_ht_destroy(ua_chan->events);
 
-       /* Wipe and free registry. */
-       ust_registry_channel_destroy(&ua_chan->session->registry, &ua_chan->registry);
+       /* Wipe and free registry from session registry. */
+       registry = get_session_registry(ua_chan->session);
+       if (registry) {
+               ust_registry_channel_del_free(registry, ua_chan->key);
+       }
 
        if (ua_chan->obj != NULL) {
                /* Remove channel from application UST object descriptor. */
@@ -312,41 +377,111 @@ void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan,
                        ERR("UST app sock %d release channel obj failed with ret %d",
                                        sock, ret);
                }
-               lttng_fd_put(LTTNG_FD_APPS, 2);
+               lttng_fd_put(LTTNG_FD_APPS, 1);
                free(ua_chan->obj);
        }
-       free(ua_chan);
+       call_rcu(&ua_chan->rcu_head, delete_ust_app_channel_rcu);
 }
 
 /*
- * For a given application and session, push metadata to consumer. The session
- * lock MUST be acquired here before calling this.
+ * Push metadata to consumer socket. The socket lock MUST be acquired.
  *
- * Return 0 on success else a negative error.
+ * On success, return the len of metadata pushed or else a negative value.
  */
-static int push_metadata(struct ust_app *app, struct ust_app_session *ua_sess)
+ssize_t ust_app_push_metadata(struct ust_registry_session *registry,
+               struct consumer_socket *socket, int send_zero_data)
 {
        int ret;
        char *metadata_str = NULL;
        size_t len, offset;
-       struct consumer_socket *socket;
+       ssize_t ret_val;
 
-       assert(app);
-       assert(ua_sess);
+       assert(registry);
+       assert(socket);
+       /* Should never be 0 which is the initial state. */
+       assert(registry->metadata_key);
 
-       if (!ua_sess->consumer || !ua_sess->metadata) {
-               /* No consumer means no stream associated so just return gracefully. */
-               ret = 0;
+       pthread_mutex_lock(&registry->lock);
+
+       offset = registry->metadata_len_sent;
+       len = registry->metadata_len - registry->metadata_len_sent;
+       if (len == 0) {
+               DBG3("No metadata to push for metadata key %" PRIu64,
+                               registry->metadata_key);
+               ret_val = len;
+               if (send_zero_data) {
+                       DBG("No metadata to push");
+                       goto push_data;
+               }
                goto end;
        }
 
+       /* Allocate only what we have to send. */
+       metadata_str = zmalloc(len);
+       if (!metadata_str) {
+               PERROR("zmalloc ust app metadata string");
+               ret_val = -ENOMEM;
+               goto error;
+       }
+       /* Copy what we haven't send out. */
+       memcpy(metadata_str, registry->metadata + offset, len);
+       registry->metadata_len_sent += len;
+
+push_data:
+       pthread_mutex_unlock(&registry->lock);
+       ret = consumer_push_metadata(socket, registry->metadata_key,
+                       metadata_str, len, offset);
+       if (ret < 0) {
+               ret_val = ret;
+               goto error_push;
+       }
+
+       free(metadata_str);
+       return len;
+
+end:
+error:
+       pthread_mutex_unlock(&registry->lock);
+error_push:
+       free(metadata_str);
+       return ret_val;
+}
+
+/*
+ * For a given application and session, push metadata to consumer. The session
+ * lock MUST be acquired here before calling this.
+ * Either sock or consumer is required : if sock is NULL, the default
+ * socket to send the metadata is retrieved from consumer, if sock
+ * is not NULL we use it to send the metadata.
+ *
+ * Return 0 on success else a negative error.
+ */
+static int push_metadata(struct ust_registry_session *registry,
+               struct consumer_output *consumer)
+{
+       int ret_val;
+       ssize_t ret;
+       struct consumer_socket *socket;
+
+       assert(registry);
+       assert(consumer);
+
        rcu_read_lock();
 
+       /*
+        * Means that no metadata was assigned to the session. This can happens if
+        * no start has been done previously.
+        */
+       if (!registry->metadata_key) {
+               ret_val = 0;
+               goto error_rcu_unlock;
+       }
+
        /* Get consumer socket to use to push the metadata.*/
-       socket = find_consumer_socket_by_bitness(app->bits_per_long,
-                       ua_sess->consumer);
+       socket = consumer_find_socket_by_bitness(registry->bits_per_long,
+                       consumer);
        if (!socket) {
-               ret = -1;
+               ret_val = -1;
                goto error_rcu_unlock;
        }
 
@@ -361,54 +496,19 @@ static int push_metadata(struct ust_app *app, struct ust_app_session *ua_sess)
         * ability to reorder the metadata it receives.
         */
        pthread_mutex_lock(socket->lock);
-       pthread_mutex_lock(&ua_sess->registry.lock);
-
-       offset = ua_sess->registry.metadata_len_sent;
-       len = ua_sess->registry.metadata_len - ua_sess->registry.metadata_len_sent;
-       if (len == 0) {
-               DBG3("No metadata to push for session id %d", ua_sess->id);
-               ret = 0;
-               goto error_reg_unlock;
-       }
-       assert(len > 0);
-
-       /* Allocate only what we have to send. */
-       metadata_str = zmalloc(len);
-       if (!metadata_str) {
-               PERROR("zmalloc ust app metadata string");
-               ret = -ENOMEM;
-               goto error_reg_unlock;
-       }
-       /* Copy what we haven't send out. */
-       memcpy(metadata_str, ua_sess->registry.metadata + offset, len);
-
-       pthread_mutex_unlock(&ua_sess->registry.lock);
-
-       ret = ust_consumer_push_metadata(socket, ua_sess, metadata_str, len,
-                       offset);
+       ret = ust_app_push_metadata(registry, socket, 0);
+       pthread_mutex_unlock(socket->lock);
        if (ret < 0) {
-               pthread_mutex_unlock(socket->lock);
+               ret_val = ret;
                goto error_rcu_unlock;
        }
 
-       /* Update len sent of the registry. */
-       pthread_mutex_lock(&ua_sess->registry.lock);
-       ua_sess->registry.metadata_len_sent += len;
-       pthread_mutex_unlock(&ua_sess->registry.lock);
-       pthread_mutex_unlock(socket->lock);
-
        rcu_read_unlock();
-       free(metadata_str);
        return 0;
 
-error_reg_unlock:
-       pthread_mutex_unlock(&ua_sess->registry.lock);
-       pthread_mutex_unlock(socket->lock);
 error_rcu_unlock:
        rcu_read_unlock();
-       free(metadata_str);
-end:
-       return ret;
+       return ret_val;
 }
 
 /*
@@ -419,45 +519,59 @@ end:
  *
  * Return 0 on success else a negative value.
  */
-static int close_metadata(struct ust_app *app, struct ust_app_session *ua_sess)
+static int close_metadata(struct ust_registry_session *registry,
+               struct consumer_output *consumer)
 {
        int ret;
        struct consumer_socket *socket;
 
-       assert(app);
-       assert(ua_sess);
+       assert(registry);
+       assert(consumer);
 
-       /* Ignore if no metadata. Valid since it can be called on unregister. */
-       if (!ua_sess->metadata) {
+       rcu_read_lock();
+
+       if (!registry->metadata_key || registry->metadata_closed) {
                ret = 0;
                goto error;
        }
 
-       rcu_read_lock();
-
        /* Get consumer socket to use to push the metadata.*/
-       socket = find_consumer_socket_by_bitness(app->bits_per_long,
-                       ua_sess->consumer);
+       socket = consumer_find_socket_by_bitness(registry->bits_per_long,
+                       consumer);
        if (!socket) {
                ret = -1;
-               goto error_rcu_unlock;
+               goto error;
        }
 
-       ret = ust_consumer_close_metadata(socket, ua_sess->metadata);
+       ret = consumer_close_metadata(socket, registry->metadata_key);
        if (ret < 0) {
-               goto error_rcu_unlock;
+               goto error;
        }
 
-error_rcu_unlock:
-       /* Destroy metadata on our side since we must not use it anymore. */
-       delete_ust_app_channel(-1, ua_sess->metadata, app);
-       ua_sess->metadata = NULL;
+       /* Metadata successfully closed. Flag the registry. */
+       registry->metadata_closed = 1;
 
-       rcu_read_unlock();
 error:
+       rcu_read_unlock();
        return ret;
 }
 
+/*
+ * We need to execute ht_destroy outside of RCU read-side critical
+ * section, so we postpone its execution using call_rcu. It is simpler
+ * than to change the semantic of the many callers of
+ * delete_ust_app_session().
+ */
+static
+void delete_ust_app_session_rcu(struct rcu_head *head)
+{
+       struct ust_app_session *ua_sess =
+               caa_container_of(head, struct ust_app_session, rcu_head);
+
+       lttng_ht_destroy(ua_sess->channels);
+       free(ua_sess);
+}
+
 /*
  * Delete ust app session safely. RCU read lock must be held before calling
  * this function.
@@ -469,15 +583,23 @@ void delete_ust_app_session(int sock, struct ust_app_session *ua_sess,
        int ret;
        struct lttng_ht_iter iter;
        struct ust_app_channel *ua_chan;
+       struct ust_registry_session *registry;
 
        assert(ua_sess);
 
-       if (ua_sess->metadata) {
+       registry = get_session_registry(ua_sess);
+       if (registry) {
                /* Push metadata for application before freeing the application. */
-               (void) push_metadata(app, ua_sess);
+               (void) push_metadata(registry, ua_sess->consumer);
 
-               /* And ask to close it for this session. */
-               (void) close_metadata(app, ua_sess);
+               /*
+                * Don't ask to close metadata for global per UID buffers. Close
+                * metadata only on destroy trace session in this case.
+                */
+               if (ua_sess->buffer_type != LTTNG_BUFFER_PER_UID) {
+                       /* And ask to close it for this session registry. */
+                       (void) close_metadata(registry, ua_sess->consumer);
+               }
        }
 
        cds_lfht_for_each_entry(ua_sess->channels->ht, &iter.iter, ua_chan,
@@ -486,9 +608,15 @@ void delete_ust_app_session(int sock, struct ust_app_session *ua_sess,
                assert(!ret);
                delete_ust_app_channel(sock, ua_chan, app);
        }
-       lttng_ht_destroy(ua_sess->channels);
 
-       ust_registry_session_destroy(&ua_sess->registry);
+       /* In case of per PID, the registry is kept in the session. */
+       if (ua_sess->buffer_type == LTTNG_BUFFER_PER_PID) {
+               struct buffer_reg_pid *reg_pid = buffer_reg_pid_find(ua_sess->id);
+               if (reg_pid) {
+                       buffer_reg_pid_remove(reg_pid);
+                       buffer_reg_pid_destroy(reg_pid);
+               }
+       }
 
        if (ua_sess->handle != -1) {
                ret = ustctl_release_handle(sock, ua_sess->handle);
@@ -497,12 +625,14 @@ void delete_ust_app_session(int sock, struct ust_app_session *ua_sess,
                                        sock, ret);
                }
        }
-       free(ua_sess);
+       call_rcu(&ua_sess->rcu_head, delete_ust_app_session_rcu);
 }
 
 /*
  * Delete a traceable application structure from the global list. Never call
  * this function outside of a call_rcu call.
+ *
+ * RCU read side lock should _NOT_ be held when calling this function.
  */
 static
 void delete_ust_app(struct ust_app *app)
@@ -510,21 +640,22 @@ void delete_ust_app(struct ust_app *app)
        int ret, sock;
        struct ust_app_session *ua_sess, *tmp_ua_sess;
 
-       rcu_read_lock();
-
        /* Delete ust app sessions info */
        sock = app->sock;
        app->sock = -1;
 
-       lttng_ht_destroy(app->sessions);
-
        /* Wipe sessions */
        cds_list_for_each_entry_safe(ua_sess, tmp_ua_sess, &app->teardown_head,
                        teardown_node) {
                /* Free every object in the session and the session. */
+               rcu_read_lock();
                delete_ust_app_session(sock, ua_sess, app);
+               rcu_read_unlock();
        }
 
+       lttng_ht_destroy(app->sessions);
+       lttng_ht_destroy(app->ust_objd);
+
        /*
         * Wait until we have deleted the application from the sock hash table
         * before closing this socket, otherwise an application could re-use the
@@ -546,8 +677,6 @@ void delete_ust_app(struct ust_app *app)
 
        DBG2("UST app pid %d deleted", app->pid);
        free(app);
-
-       rcu_read_unlock();
 }
 
 /*
@@ -610,21 +739,9 @@ struct ust_app_session *alloc_ust_app_session(struct ust_app *app)
        ua_sess->handle = -1;
        ua_sess->channels = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
        pthread_mutex_init(&ua_sess->lock, NULL);
-       if (ust_registry_session_init(&ua_sess->registry, app,
-                       app->bits_per_long,
-                       app->uint8_t_alignment,
-                       app->uint16_t_alignment,
-                       app->uint32_t_alignment,
-                       app->uint64_t_alignment,
-                       app->long_alignment,
-                       app->byte_order)) {
-               goto error;
-       }
 
        return ua_sess;
 
-error:
-       free(ua_sess);
 error_free:
        return NULL;
 }
@@ -652,6 +769,7 @@ struct ust_app_channel *alloc_ust_app_channel(char *name,
 
        ua_chan->enabled = 1;
        ua_chan->handle = -1;
+       ua_chan->session = ua_sess;
        ua_chan->key = get_next_channel_key();
        ua_chan->ctx = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
        ua_chan->events = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
@@ -659,9 +777,6 @@ struct ust_app_channel *alloc_ust_app_channel(char *name,
 
        CDS_INIT_LIST_HEAD(&ua_chan->streams.head);
 
-       /* Initialize UST registry. */
-       ust_registry_channel_init(&ua_sess->registry, &ua_chan->registry);
-
        /* Copy attributes */
        if (attr) {
                /* Translate from lttng_ust_channel to ustctl_consumer_channel_attr. */
@@ -1060,69 +1175,24 @@ error:
 }
 
 /*
- * Create the specified channel onto the UST tracer for a UST session. This
- * MUST be called with UST app session lock held.
+ * Send channel and stream buffer to application.
  *
  * Return 0 on success. On error, a negative value is returned.
  */
-static int create_ust_channel(struct ust_app *app,
-               struct ust_app_session *ua_sess, struct ust_app_channel *ua_chan,
-               struct consumer_output *consumer)
+static int send_channel_pid_to_ust(struct ust_app *app,
+               struct ust_app_session *ua_sess, struct ust_app_channel *ua_chan)
 {
        int ret;
-       unsigned int nb_fd = 0;
-       struct consumer_socket *socket;
        struct ust_app_stream *stream, *stmp;
 
        assert(app);
        assert(ua_sess);
        assert(ua_chan);
-       assert(consumer);
-
-       rcu_read_lock();
-       health_code_update();
-
-       /* Get the right consumer socket for the application. */
-       socket = find_consumer_socket_by_bitness(app->bits_per_long, consumer);
-       if (!socket) {
-               ret = -1;
-               goto error;
-       }
-
-       health_code_update();
-
-       /*
-        * Ask consumer to create channel. The consumer will return the number of
-        * stream we have to expect.
-        */
-       ret = ust_consumer_ask_channel(ua_sess, ua_chan, consumer, socket);
-       if (ret < 0) {
-               goto error;
-       }
-
-       /*
-        * Compute the number of fd needed before receiving them. It must be 2 per
-        * stream (2 being the default value here).
-        */
-       nb_fd = DEFAULT_UST_STREAM_FD_NUM * ua_chan->expected_stream_count;
-
-       /* Reserve the amount of file descriptor we need. */
-       ret = lttng_fd_get(LTTNG_FD_APPS, nb_fd);
-       if (ret < 0) {
-               ERR("Exhausted number of available FD upon create channel");
-               goto error_fd_get;
-       }
 
        health_code_update();
 
-       /*
-        * Now get the channel from the consumer. This call wil populate the stream
-        * list of that channel and set the ust object.
-        */
-       ret = ust_consumer_get_channel(socket, ua_chan);
-       if (ret < 0) {
-               goto error_destroy;
-       }
+       DBG("UST app sending channel %s to UST app sock %d", ua_chan->name,
+                       app->sock);
 
        /* Send channel to the application. */
        ret = ust_consumer_send_channel_to_ust(app, ua_sess, ua_chan);
@@ -1142,43 +1212,13 @@ static int create_ust_channel(struct ust_app *app,
                cds_list_del(&stream->list);
                delete_ust_app_stream(-1, stream);
        }
-
        /* Flag the channel that it is sent to the application. */
        ua_chan->is_sent = 1;
-       /* Assign session to channel. */
-       ua_chan->session = ua_sess;
-       /* Initialize ust objd object using the received handle and add it. */
-       lttng_ht_node_init_ulong(&ua_chan->ust_objd_node, ua_chan->handle);
-       lttng_ht_add_unique_ulong(app->ust_objd, &ua_chan->ust_objd_node);
 
+error:
        health_code_update();
-
-       /* If channel is not enabled, disable it on the tracer */
-       if (!ua_chan->enabled) {
-               ret = disable_ust_channel(app, ua_sess, ua_chan);
-               if (ret < 0) {
-                       goto error;
-               }
-       }
-
-       rcu_read_unlock();
-       return 0;
-
-error_destroy:
-       lttng_fd_put(LTTNG_FD_APPS, nb_fd);
-error_fd_get:
-       /*
-        * Initiate a destroy channel on the consumer since we had an error
-        * handling it on our side. The return value is of no importance since we
-        * already have a ret value set by the previous error that we need to
-        * return.
-        */
-       (void) ust_consumer_destroy_channel(socket, ua_chan);
-error:
-       health_code_update();
-       rcu_read_unlock();
-       return ret;
-}
+       return ret;
+}
 
 /*
  * Create the specified event onto the UST tracer for a UST session.
@@ -1288,6 +1328,9 @@ static void shadow_copy_channel(struct ust_app_channel *ua_chan,
        strncpy(ua_chan->name, uchan->name, sizeof(ua_chan->name));
        ua_chan->name[sizeof(ua_chan->name) - 1] = '\0';
 
+       ua_chan->tracefile_size = uchan->tracefile_size;
+       ua_chan->tracefile_count = uchan->tracefile_count;
+
        /* Copy event attributes since the layout is different. */
        ua_chan->attr.subbuf_size = uchan->attr.subbuf_size;
        ua_chan->attr.num_subbuf = uchan->attr.num_subbuf;
@@ -1301,6 +1344,7 @@ static void shadow_copy_channel(struct ust_app_channel *ua_chan,
         */
 
        ua_chan->enabled = uchan->enabled;
+       ua_chan->tracing_channel_id = uchan->id;
 
        cds_lfht_for_each_entry(uchan->ctx->ht, &iter.iter, uctx, node.node) {
                ua_ctx = alloc_ust_app_ctx(&uctx->ctx);
@@ -1353,20 +1397,37 @@ static void shadow_copy_session(struct ust_app_session *ua_sess,
 
        DBG2("Shadow copy of session handle %d", ua_sess->handle);
 
-       ua_sess->id = usess->id;
-       ua_sess->uid = usess->uid;
-       ua_sess->gid = usess->gid;
-
-       ret = snprintf(ua_sess->path, PATH_MAX, "%s-%d-%s/", app->name, app->pid,
-                       datetime);
+       ua_sess->tracing_id = usess->id;
+       ua_sess->id = get_next_session_id();
+       ua_sess->uid = app->uid;
+       ua_sess->gid = app->gid;
+       ua_sess->euid = usess->uid;
+       ua_sess->egid = usess->gid;
+       ua_sess->buffer_type = usess->buffer_type;
+       ua_sess->bits_per_long = app->bits_per_long;
+       /* There is only one consumer object per session possible. */
+       ua_sess->consumer = usess->consumer;
+
+       switch (ua_sess->buffer_type) {
+       case LTTNG_BUFFER_PER_PID:
+               ret = snprintf(ua_sess->path, sizeof(ua_sess->path),
+                               DEFAULT_UST_TRACE_PID_PATH "/%s-%d-%s", app->name, app->pid,
+                               datetime);
+               break;
+       case LTTNG_BUFFER_PER_UID:
+               ret = snprintf(ua_sess->path, sizeof(ua_sess->path),
+                               DEFAULT_UST_TRACE_UID_PATH, ua_sess->uid, app->bits_per_long);
+               break;
+       default:
+               assert(0);
+               goto error;
+       }
        if (ret < 0) {
                PERROR("asprintf UST shadow copy session");
-               /* TODO: We cannot return an error from here.. */
                assert(0);
+               goto error;
        }
 
-       /* TODO: support all UST domain */
-
        /* Iterate over all channels in global domain. */
        cds_lfht_for_each_entry(usess->domain_global.channels->ht, &iter.iter,
                        uchan, node.node) {
@@ -1396,6 +1457,9 @@ static void shadow_copy_session(struct ust_app_session *ua_sess,
 
                lttng_ht_add_unique_str(ua_sess->channels, &ua_chan->node);
        }
+
+error:
+       return;
 }
 
 /*
@@ -1431,6 +1495,119 @@ error:
        return NULL;
 }
 
+/*
+ * Setup buffer registry per PID for the given session and application. If none
+ * is found, a new one is created, added to the global registry and
+ * initialized. If regp is valid, it's set with the newly created object.
+ *
+ * Return 0 on success or else a negative value.
+ */
+static int setup_buffer_reg_pid(struct ust_app_session *ua_sess,
+               struct ust_app *app, struct buffer_reg_pid **regp)
+{
+       int ret = 0;
+       struct buffer_reg_pid *reg_pid;
+
+       assert(ua_sess);
+       assert(app);
+
+       rcu_read_lock();
+
+       reg_pid = buffer_reg_pid_find(ua_sess->id);
+       if (!reg_pid) {
+               /*
+                * This is the create channel path meaning that if there is NO
+                * registry available, we have to create one for this session.
+                */
+               ret = buffer_reg_pid_create(ua_sess->id, &reg_pid);
+               if (ret < 0) {
+                       goto error;
+               }
+               buffer_reg_pid_add(reg_pid);
+       } else {
+               goto end;
+       }
+
+       /* Initialize registry. */
+       ret = ust_registry_session_init(&reg_pid->registry->reg.ust, app,
+                       app->bits_per_long, app->uint8_t_alignment,
+                       app->uint16_t_alignment, app->uint32_t_alignment,
+                       app->uint64_t_alignment, app->long_alignment,
+                       app->byte_order, app->version.major,
+                       app->version.minor);
+       if (ret < 0) {
+               goto error;
+       }
+
+       DBG3("UST app buffer registry per PID created successfully");
+
+end:
+       if (regp) {
+               *regp = reg_pid;
+       }
+error:
+       rcu_read_unlock();
+       return ret;
+}
+
+/*
+ * Setup buffer registry per UID for the given session and application. If none
+ * is found, a new one is created, added to the global registry and
+ * initialized. If regp is valid, it's set with the newly created object.
+ *
+ * Return 0 on success or else a negative value.
+ */
+static int setup_buffer_reg_uid(struct ltt_ust_session *usess,
+               struct ust_app *app, struct buffer_reg_uid **regp)
+{
+       int ret = 0;
+       struct buffer_reg_uid *reg_uid;
+
+       assert(usess);
+       assert(app);
+
+       rcu_read_lock();
+
+       reg_uid = buffer_reg_uid_find(usess->id, app->bits_per_long, app->uid);
+       if (!reg_uid) {
+               /*
+                * This is the create channel path meaning that if there is NO
+                * registry available, we have to create one for this session.
+                */
+               ret = buffer_reg_uid_create(usess->id, app->bits_per_long, app->uid,
+                               LTTNG_DOMAIN_UST, &reg_uid);
+               if (ret < 0) {
+                       goto error;
+               }
+               buffer_reg_uid_add(reg_uid);
+       } else {
+               goto end;
+       }
+
+       /* Initialize registry. */
+       ret = ust_registry_session_init(&reg_uid->registry->reg.ust, NULL,
+                       app->bits_per_long, app->uint8_t_alignment,
+                       app->uint16_t_alignment, app->uint32_t_alignment,
+                       app->uint64_t_alignment, app->long_alignment,
+                       app->byte_order, app->version.major,
+                       app->version.minor);
+       if (ret < 0) {
+               goto error;
+       }
+       /* Add node to teardown list of the session. */
+       cds_list_add(&reg_uid->lnode, &usess->buffer_reg_uid_list);
+
+       DBG3("UST app buffer registry per UID created successfully");
+
+end:
+       if (regp) {
+               *regp = reg_uid;
+       }
+error:
+       rcu_read_unlock();
+       return ret;
+}
+
 /*
  * Create a session on the tracer side for the given app.
  *
@@ -1469,6 +1646,27 @@ static int create_ust_app_session(struct ltt_ust_session *usess,
                created = 1;
        }
 
+       switch (usess->buffer_type) {
+       case LTTNG_BUFFER_PER_PID:
+               /* Init local registry. */
+               ret = setup_buffer_reg_pid(ua_sess, app, NULL);
+               if (ret < 0) {
+                       goto error;
+               }
+               break;
+       case LTTNG_BUFFER_PER_UID:
+               /* Look for a global registry. If none exists, create one. */
+               ret = setup_buffer_reg_uid(usess, app, NULL);
+               if (ret < 0) {
+                       goto error;
+               }
+               break;
+       default:
+               assert(0);
+               ret = -EINVAL;
+               goto error;
+       }
+
        health_code_update();
 
        if (ua_sess->handle == -1) {
@@ -1494,20 +1692,13 @@ static int create_ust_app_session(struct ltt_ust_session *usess,
                ua_sess->handle = ret;
 
                /* Add ust app session to app's HT */
-               lttng_ht_node_init_ulong(&ua_sess->node, (unsigned long) ua_sess->id);
+               lttng_ht_node_init_ulong(&ua_sess->node,
+                               (unsigned long) ua_sess->tracing_id);
                lttng_ht_add_unique_ulong(app->sessions, &ua_sess->node);
 
                DBG2("UST app session created successfully with handle %d", ret);
        }
 
-       /*
-        * Assign consumer if not already set. For one application, there is only
-        * one possible consumer has of now.
-        */
-       if (!ua_sess->consumer) {
-               ua_sess->consumer = usess->consumer;
-       }
-
        *ua_sess_ptr = ua_sess;
        if (is_created) {
                *is_created = created;
@@ -1524,7 +1715,7 @@ error:
 /*
  * Create a context for the channel on the tracer.
  *
- * Called with UST app session lock held.
+ * Called with UST app session lock held and a RCU read side lock.
  */
 static
 int create_ust_app_channel_context(struct ust_app_session *ua_sess,
@@ -1538,24 +1729,538 @@ int create_ust_app_channel_context(struct ust_app_session *ua_sess,
 
        DBG2("UST app adding context to channel %s", ua_chan->name);
 
-       lttng_ht_lookup(ua_chan->ctx, (void *)((unsigned long)uctx->ctx), &iter);
-       node = lttng_ht_iter_get_node_ulong(&iter);
-       if (node != NULL) {
-               ret = -EEXIST;
-               goto error;
-       }
+       lttng_ht_lookup(ua_chan->ctx, (void *)((unsigned long)uctx->ctx), &iter);
+       node = lttng_ht_iter_get_node_ulong(&iter);
+       if (node != NULL) {
+               ret = -EEXIST;
+               goto error;
+       }
+
+       ua_ctx = alloc_ust_app_ctx(uctx);
+       if (ua_ctx == NULL) {
+               /* malloc failed */
+               ret = -1;
+               goto error;
+       }
+
+       lttng_ht_node_init_ulong(&ua_ctx->node, (unsigned long) ua_ctx->ctx.ctx);
+       lttng_ht_add_unique_ulong(ua_chan->ctx, &ua_ctx->node);
+
+       ret = create_ust_channel_context(ua_chan, ua_ctx, app);
+       if (ret < 0) {
+               goto error;
+       }
+
+error:
+       return ret;
+}
+
+/*
+ * Enable on the tracer side a ust app event for the session and channel.
+ *
+ * Called with UST app session lock held.
+ */
+static
+int enable_ust_app_event(struct ust_app_session *ua_sess,
+               struct ust_app_event *ua_event, struct ust_app *app)
+{
+       int ret;
+
+       ret = enable_ust_event(app, ua_sess, ua_event);
+       if (ret < 0) {
+               goto error;
+       }
+
+       ua_event->enabled = 1;
+
+error:
+       return ret;
+}
+
+/*
+ * Disable on the tracer side a ust app event for the session and channel.
+ */
+static int disable_ust_app_event(struct ust_app_session *ua_sess,
+               struct ust_app_event *ua_event, struct ust_app *app)
+{
+       int ret;
+
+       ret = disable_ust_event(app, ua_sess, ua_event);
+       if (ret < 0) {
+               goto error;
+       }
+
+       ua_event->enabled = 0;
+
+error:
+       return ret;
+}
+
+/*
+ * Lookup ust app channel for session and disable it on the tracer side.
+ */
+static
+int disable_ust_app_channel(struct ust_app_session *ua_sess,
+               struct ust_app_channel *ua_chan, struct ust_app *app)
+{
+       int ret;
+
+       ret = disable_ust_channel(app, ua_sess, ua_chan);
+       if (ret < 0) {
+               goto error;
+       }
+
+       ua_chan->enabled = 0;
+
+error:
+       return ret;
+}
+
+/*
+ * Lookup ust app channel for session and enable it on the tracer side. This
+ * MUST be called with a RCU read side lock acquired.
+ */
+static int enable_ust_app_channel(struct ust_app_session *ua_sess,
+               struct ltt_ust_channel *uchan, struct ust_app *app)
+{
+       int ret = 0;
+       struct lttng_ht_iter iter;
+       struct lttng_ht_node_str *ua_chan_node;
+       struct ust_app_channel *ua_chan;
+
+       lttng_ht_lookup(ua_sess->channels, (void *)uchan->name, &iter);
+       ua_chan_node = lttng_ht_iter_get_node_str(&iter);
+       if (ua_chan_node == NULL) {
+               DBG2("Unable to find channel %s in ust session id %u",
+                               uchan->name, ua_sess->tracing_id);
+               goto error;
+       }
+
+       ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
+
+       ret = enable_ust_channel(app, ua_sess, ua_chan);
+       if (ret < 0) {
+               goto error;
+       }
+
+error:
+       return ret;
+}
+
+/*
+ * Ask the consumer to create a channel and get it if successful.
+ *
+ * Return 0 on success or else a negative value.
+ */
+static int do_consumer_create_channel(struct ltt_ust_session *usess,
+               struct ust_app_session *ua_sess, struct ust_app_channel *ua_chan,
+               int bitness, struct ust_registry_session *registry)
+{
+       int ret;
+       unsigned int nb_fd = 0;
+       struct consumer_socket *socket;
+
+       assert(usess);
+       assert(ua_sess);
+       assert(ua_chan);
+       assert(registry);
+
+       rcu_read_lock();
+       health_code_update();
+
+       /* Get the right consumer socket for the application. */
+       socket = consumer_find_socket_by_bitness(bitness, usess->consumer);
+       if (!socket) {
+               ret = -EINVAL;
+               goto error;
+       }
+
+       health_code_update();
+
+       /* Need one fd for the channel. */
+       ret = lttng_fd_get(LTTNG_FD_APPS, 1);
+       if (ret < 0) {
+               ERR("Exhausted number of available FD upon create channel");
+               goto error;
+       }
+
+       /*
+        * Ask consumer to create channel. The consumer will return the number of
+        * stream we have to expect.
+        */
+       ret = ust_consumer_ask_channel(ua_sess, ua_chan, usess->consumer, socket,
+                       registry);
+       if (ret < 0) {
+               goto error_ask;
+       }
+
+       /*
+        * Compute the number of fd needed before receiving them. It must be 2 per
+        * stream (2 being the default value here).
+        */
+       nb_fd = DEFAULT_UST_STREAM_FD_NUM * ua_chan->expected_stream_count;
+
+       /* Reserve the amount of file descriptor we need. */
+       ret = lttng_fd_get(LTTNG_FD_APPS, nb_fd);
+       if (ret < 0) {
+               ERR("Exhausted number of available FD upon create channel");
+               goto error_fd_get_stream;
+       }
+
+       health_code_update();
+
+       /*
+        * Now get the channel from the consumer. This call wil populate the stream
+        * list of that channel and set the ust objects.
+        */
+       ret = ust_consumer_get_channel(socket, ua_chan);
+       if (ret < 0) {
+               goto error_destroy;
+       }
+
+       rcu_read_unlock();
+       return 0;
+
+error_destroy:
+       lttng_fd_put(LTTNG_FD_APPS, nb_fd);
+error_fd_get_stream:
+       /*
+        * Initiate a destroy channel on the consumer since we had an error
+        * handling it on our side. The return value is of no importance since we
+        * already have a ret value set by the previous error that we need to
+        * return.
+        */
+       (void) ust_consumer_destroy_channel(socket, ua_chan);
+error_ask:
+       lttng_fd_put(LTTNG_FD_APPS, 1);
+error:
+       health_code_update();
+       rcu_read_unlock();
+       return ret;
+}
+
+/*
+ * Duplicate the ust data object of the ust app stream and save it in the
+ * buffer registry stream.
+ *
+ * Return 0 on success or else a negative value.
+ */
+static int duplicate_stream_object(struct buffer_reg_stream *reg_stream,
+               struct ust_app_stream *stream)
+{
+       int ret;
+
+       assert(reg_stream);
+       assert(stream);
+
+       /* Reserve the amount of file descriptor we need. */
+       ret = lttng_fd_get(LTTNG_FD_APPS, 2);
+       if (ret < 0) {
+               ERR("Exhausted number of available FD upon duplicate stream");
+               goto error;
+       }
+
+       /* Duplicate object for stream once the original is in the registry. */
+       ret = ustctl_duplicate_ust_object_data(&stream->obj,
+                       reg_stream->obj.ust);
+       if (ret < 0) {
+               ERR("Duplicate stream obj from %p to %p failed with ret %d",
+                               reg_stream->obj.ust, stream->obj, ret);
+               lttng_fd_put(LTTNG_FD_APPS, 2);
+               goto error;
+       }
+       stream->handle = stream->obj->handle;
+
+error:
+       return ret;
+}
+
+/*
+ * Duplicate the ust data object of the ust app. channel and save it in the
+ * buffer registry channel.
+ *
+ * Return 0 on success or else a negative value.
+ */
+static int duplicate_channel_object(struct buffer_reg_channel *reg_chan,
+               struct ust_app_channel *ua_chan)
+{
+       int ret;
+
+       assert(reg_chan);
+       assert(ua_chan);
+
+       /* Need two fds for the channel. */
+       ret = lttng_fd_get(LTTNG_FD_APPS, 1);
+       if (ret < 0) {
+               ERR("Exhausted number of available FD upon duplicate channel");
+               goto error_fd_get;
+       }
+
+       /* Duplicate object for stream once the original is in the registry. */
+       ret = ustctl_duplicate_ust_object_data(&ua_chan->obj, reg_chan->obj.ust);
+       if (ret < 0) {
+               ERR("Duplicate channel obj from %p to %p failed with ret: %d",
+                               reg_chan->obj.ust, ua_chan->obj, ret);
+               goto error;
+       }
+       ua_chan->handle = ua_chan->obj->handle;
+
+       return 0;
+
+error:
+       lttng_fd_put(LTTNG_FD_APPS, 1);
+error_fd_get:
+       return ret;
+}
+
+/*
+ * For a given channel buffer registry, setup all streams of the given ust
+ * application channel.
+ *
+ * Return 0 on success or else a negative value.
+ */
+static int setup_buffer_reg_streams(struct buffer_reg_channel *reg_chan,
+               struct ust_app_channel *ua_chan)
+{
+       int ret = 0;
+       struct ust_app_stream *stream, *stmp;
+
+       assert(reg_chan);
+       assert(ua_chan);
+
+       DBG2("UST app setup buffer registry stream");
+
+       /* Send all streams to application. */
+       cds_list_for_each_entry_safe(stream, stmp, &ua_chan->streams.head, list) {
+               struct buffer_reg_stream *reg_stream;
+
+               ret = buffer_reg_stream_create(&reg_stream);
+               if (ret < 0) {
+                       goto error;
+               }
+
+               /*
+                * Keep original pointer and nullify it in the stream so the delete
+                * stream call does not release the object.
+                */
+               reg_stream->obj.ust = stream->obj;
+               stream->obj = NULL;
+               buffer_reg_stream_add(reg_stream, reg_chan);
+
+               /* We don't need the streams anymore. */
+               cds_list_del(&stream->list);
+               delete_ust_app_stream(-1, stream);
+       }
+
+error:
+       return ret;
+}
+
+/*
+ * Create a buffer registry channel for the given session registry and
+ * application channel object. If regp pointer is valid, it's set with the
+ * created object. Important, the created object is NOT added to the session
+ * registry hash table.
+ *
+ * Return 0 on success else a negative value.
+ */
+static int create_buffer_reg_channel(struct buffer_reg_session *reg_sess,
+               struct ust_app_channel *ua_chan, struct buffer_reg_channel **regp)
+{
+       int ret;
+       struct buffer_reg_channel *reg_chan = NULL;
+
+       assert(reg_sess);
+       assert(ua_chan);
+
+       DBG2("UST app creating buffer registry channel for %s", ua_chan->name);
+
+       /* Create buffer registry channel. */
+       ret = buffer_reg_channel_create(ua_chan->tracing_channel_id, &reg_chan);
+       if (ret < 0) {
+               goto error_create;
+       }
+       assert(reg_chan);
+       reg_chan->consumer_key = ua_chan->key;
+
+       /* Create and add a channel registry to session. */
+       ret = ust_registry_channel_add(reg_sess->reg.ust,
+                       ua_chan->tracing_channel_id);
+       if (ret < 0) {
+               goto error;
+       }
+       buffer_reg_channel_add(reg_sess, reg_chan);
+
+       if (regp) {
+               *regp = reg_chan;
+       }
+
+       return 0;
+
+error:
+       /* Safe because the registry channel object was not added to any HT. */
+       buffer_reg_channel_destroy(reg_chan, LTTNG_DOMAIN_UST);
+error_create:
+       return ret;
+}
+
+/*
+ * Setup buffer registry channel for the given session registry and application
+ * channel object. If regp pointer is valid, it's set with the created object.
+ *
+ * Return 0 on success else a negative value.
+ */
+static int setup_buffer_reg_channel(struct buffer_reg_session *reg_sess,
+               struct ust_app_channel *ua_chan, struct buffer_reg_channel *reg_chan)
+{
+       int ret;
+
+       assert(reg_sess);
+       assert(reg_chan);
+       assert(ua_chan);
+       assert(ua_chan->obj);
+
+       DBG2("UST app setup buffer registry channel for %s", ua_chan->name);
+
+       /* Setup all streams for the registry. */
+       ret = setup_buffer_reg_streams(reg_chan, ua_chan);
+       if (ret < 0) {
+               goto error;
+       }
+
+       reg_chan->obj.ust = ua_chan->obj;
+       ua_chan->obj = NULL;
+
+       return 0;
+
+error:
+       buffer_reg_channel_remove(reg_sess, reg_chan);
+       buffer_reg_channel_destroy(reg_chan, LTTNG_DOMAIN_UST);
+       return ret;
+}
+
+/*
+ * Send buffer registry channel to the application.
+ *
+ * Return 0 on success else a negative value.
+ */
+static int send_channel_uid_to_ust(struct buffer_reg_channel *reg_chan,
+               struct ust_app *app, struct ust_app_session *ua_sess,
+               struct ust_app_channel *ua_chan)
+{
+       int ret;
+       struct buffer_reg_stream *reg_stream;
+
+       assert(reg_chan);
+       assert(app);
+       assert(ua_sess);
+       assert(ua_chan);
+
+       DBG("UST app sending buffer registry channel to ust sock %d", app->sock);
+
+       ret = duplicate_channel_object(reg_chan, ua_chan);
+       if (ret < 0) {
+               goto error;
+       }
+
+       /* Send channel to the application. */
+       ret = ust_consumer_send_channel_to_ust(app, ua_sess, ua_chan);
+       if (ret < 0) {
+               goto error;
+       }
+
+       health_code_update();
+
+       /* Send all streams to application. */
+       pthread_mutex_lock(&reg_chan->stream_list_lock);
+       cds_list_for_each_entry(reg_stream, &reg_chan->streams, lnode) {
+               struct ust_app_stream stream;
+
+               ret = duplicate_stream_object(reg_stream, &stream);
+               if (ret < 0) {
+                       goto error_stream_unlock;
+               }
+
+               ret = ust_consumer_send_stream_to_ust(app, ua_chan, &stream);
+               if (ret < 0) {
+                       (void) release_ust_app_stream(-1, &stream);
+                       goto error_stream_unlock;
+               }
+
+               /*
+                * The return value is not important here. This function will output an
+                * error if needed.
+                */
+               (void) release_ust_app_stream(-1, &stream);
+       }
+       ua_chan->is_sent = 1;
+
+error_stream_unlock:
+       pthread_mutex_unlock(&reg_chan->stream_list_lock);
+error:
+       return ret;
+}
+
+/*
+ * Create and send to the application the created buffers with per UID buffers.
+ *
+ * Return 0 on success else a negative value.
+ */
+static int create_channel_per_uid(struct ust_app *app,
+               struct ltt_ust_session *usess, struct ust_app_session *ua_sess,
+               struct ust_app_channel *ua_chan)
+{
+       int ret;
+       struct buffer_reg_uid *reg_uid;
+       struct buffer_reg_channel *reg_chan;
+
+       assert(app);
+       assert(usess);
+       assert(ua_sess);
+       assert(ua_chan);
+
+       DBG("UST app creating channel %s with per UID buffers", ua_chan->name);
+
+       reg_uid = buffer_reg_uid_find(usess->id, app->bits_per_long, app->uid);
+       /*
+        * The session creation handles the creation of this global registry
+        * object. If none can be find, there is a code flow problem or a
+        * teardown race.
+        */
+       assert(reg_uid);
+
+       reg_chan = buffer_reg_channel_find(ua_chan->tracing_channel_id,
+                       reg_uid);
+       if (!reg_chan) {
+               /* Create the buffer registry channel object. */
+               ret = create_buffer_reg_channel(reg_uid->registry, ua_chan, &reg_chan);
+               if (ret < 0) {
+                       goto error;
+               }
+               assert(reg_chan);
+
+               /*
+                * Create the buffers on the consumer side. This call populates the
+                * ust app channel object with all streams and data object.
+                */
+               ret = do_consumer_create_channel(usess, ua_sess, ua_chan,
+                               app->bits_per_long, reg_uid->registry->reg.ust);
+               if (ret < 0) {
+                       goto error;
+               }
+
+               /*
+                * Setup the streams and add it to the session registry.
+                */
+               ret = setup_buffer_reg_channel(reg_uid->registry, ua_chan, reg_chan);
+               if (ret < 0) {
+                       goto error;
+               }
 
-       ua_ctx = alloc_ust_app_ctx(uctx);
-       if (ua_ctx == NULL) {
-               /* malloc failed */
-               ret = -1;
-               goto error;
        }
 
-       lttng_ht_node_init_ulong(&ua_ctx->node, (unsigned long) ua_ctx->ctx.ctx);
-       lttng_ht_add_unique_ulong(ua_chan->ctx, &ua_ctx->node);
-
-       ret = create_ust_channel_context(ua_chan, ua_ctx, app);
+       /* Send buffers to the application. */
+       ret = send_channel_uid_to_ust(reg_chan, app, ua_sess, ua_chan);
        if (ret < 0) {
                goto error;
        }
@@ -1565,90 +2270,104 @@ error:
 }
 
 /*
- * Enable on the tracer side a ust app event for the session and channel.
+ * Create and send to the application the created buffers with per PID buffers.
  *
- * Called with UST app session lock held.
+ * Return 0 on success else a negative value.
  */
-static
-int enable_ust_app_event(struct ust_app_session *ua_sess,
-               struct ust_app_event *ua_event, struct ust_app *app)
+static int create_channel_per_pid(struct ust_app *app,
+               struct ltt_ust_session *usess, struct ust_app_session *ua_sess,
+               struct ust_app_channel *ua_chan)
 {
        int ret;
+       struct ust_registry_session *registry;
 
-       ret = enable_ust_event(app, ua_sess, ua_event);
-       if (ret < 0) {
-               goto error;
-       }
+       assert(app);
+       assert(usess);
+       assert(ua_sess);
+       assert(ua_chan);
 
-       ua_event->enabled = 1;
+       DBG("UST app creating channel %s with per PID buffers", ua_chan->name);
 
-error:
-       return ret;
-}
+       rcu_read_lock();
 
-/*
- * Disable on the tracer side a ust app event for the session and channel.
- */
-static int disable_ust_app_event(struct ust_app_session *ua_sess,
-               struct ust_app_event *ua_event, struct ust_app *app)
-{
-       int ret;
+       registry = get_session_registry(ua_sess);
+       assert(registry);
 
-       ret = disable_ust_event(app, ua_sess, ua_event);
+       /* Create and add a new channel registry to session. */
+       ret = ust_registry_channel_add(registry, ua_chan->key);
        if (ret < 0) {
                goto error;
        }
 
-       ua_event->enabled = 0;
-
-error:
-       return ret;
-}
-
-/*
- * Lookup ust app channel for session and disable it on the tracer side.
- */
-static
-int disable_ust_app_channel(struct ust_app_session *ua_sess,
-               struct ust_app_channel *ua_chan, struct ust_app *app)
-{
-       int ret;
-
-       ret = disable_ust_channel(app, ua_sess, ua_chan);
+       /* Create and get channel on the consumer side. */
+       ret = do_consumer_create_channel(usess, ua_sess, ua_chan,
+                       app->bits_per_long, registry);
        if (ret < 0) {
                goto error;
        }
 
-       ua_chan->enabled = 0;
+       ret = send_channel_pid_to_ust(app, ua_sess, ua_chan);
+       if (ret < 0) {
+               goto error;
+       }
 
 error:
+       rcu_read_unlock();
        return ret;
 }
 
 /*
- * Lookup ust app channel for session and enable it on the tracer side.
+ * From an already allocated ust app channel, create the channel buffers if
+ * need and send it to the application. This MUST be called with a RCU read
+ * side lock acquired.
+ *
+ * Return 0 on success or else a negative value.
  */
-static int enable_ust_app_channel(struct ust_app_session *ua_sess,
-               struct ltt_ust_channel *uchan, struct ust_app *app)
+static int do_create_channel(struct ust_app *app,
+               struct ltt_ust_session *usess, struct ust_app_session *ua_sess,
+               struct ust_app_channel *ua_chan)
 {
-       int ret = 0;
-       struct lttng_ht_iter iter;
-       struct lttng_ht_node_str *ua_chan_node;
-       struct ust_app_channel *ua_chan;
+       int ret;
 
-       lttng_ht_lookup(ua_sess->channels, (void *)uchan->name, &iter);
-       ua_chan_node = lttng_ht_iter_get_node_str(&iter);
-       if (ua_chan_node == NULL) {
-               DBG2("Unable to find channel %s in ust session id %u",
-                               uchan->name, ua_sess->id);
+       assert(app);
+       assert(usess);
+       assert(ua_sess);
+       assert(ua_chan);
+
+       /* Handle buffer type before sending the channel to the application. */
+       switch (usess->buffer_type) {
+       case LTTNG_BUFFER_PER_UID:
+       {
+               ret = create_channel_per_uid(app, usess, ua_sess, ua_chan);
+               if (ret < 0) {
+                       goto error;
+               }
+               break;
+       }
+       case LTTNG_BUFFER_PER_PID:
+       {
+               ret = create_channel_per_pid(app, usess, ua_sess, ua_chan);
+               if (ret < 0) {
+                       goto error;
+               }
+               break;
+       }
+       default:
+               assert(0);
+               ret = -EINVAL;
                goto error;
        }
 
-       ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
+       /* Initialize ust objd object using the received handle and add it. */
+       lttng_ht_node_init_ulong(&ua_chan->ust_objd_node, ua_chan->handle);
+       lttng_ht_add_unique_ulong(app->ust_objd, &ua_chan->ust_objd_node);
 
-       ret = enable_ust_channel(app, ua_sess, ua_chan);
-       if (ret < 0) {
-               goto error;
+       /* If channel is not enabled, disable it on the tracer */
+       if (!ua_chan->enabled) {
+               ret = disable_ust_channel(app, ua_sess, ua_chan);
+               if (ret < 0) {
+                       goto error;
+               }
        }
 
 error:
@@ -1659,11 +2378,13 @@ error:
  * Create UST app channel and create it on the tracer. Set ua_chanp of the
  * newly created channel if not NULL.
  *
- * Called with UST app session lock held.
+ * Called with UST app session lock and RCU read-side lock held.
+ *
+ * Return 0 on success or else a negative value.
  */
 static int create_ust_app_channel(struct ust_app_session *ua_sess,
                struct ltt_ust_channel *uchan, struct ust_app *app,
-               struct consumer_output *consumer, enum lttng_ust_chan_type type,
+               enum lttng_ust_chan_type type, struct ltt_ust_session *usess,
                struct ust_app_channel **ua_chanp)
 {
        int ret = 0;
@@ -1690,7 +2411,7 @@ static int create_ust_app_channel(struct ust_app_session *ua_sess,
        /* Set channel type. */
        ua_chan->attr.type = type;
 
-       ret = create_ust_channel(app, ua_sess, ua_chan, consumer);
+       ret = do_create_channel(app, usess, ua_sess, ua_chan);
        if (ret < 0) {
                goto error;
        }
@@ -1769,22 +2490,28 @@ error:
 /*
  * Create UST metadata and open it on the tracer side.
  *
- * Called with UST app session lock held.
+ * Called with UST app session lock held and RCU read side lock.
  */
 static int create_ust_app_metadata(struct ust_app_session *ua_sess,
-               struct ust_app *app, struct consumer_output *consumer)
+               struct ust_app *app, struct consumer_output *consumer,
+               struct ustctl_consumer_channel_attr *attr)
 {
        int ret = 0;
        struct ust_app_channel *metadata;
        struct consumer_socket *socket;
+       struct ust_registry_session *registry;
 
        assert(ua_sess);
        assert(app);
        assert(consumer);
 
-       if (ua_sess->metadata) {
-               /* Already exist. Return success. */
-               goto end;
+       registry = get_session_registry(ua_sess);
+       assert(registry);
+
+       /* Metadata already exists for this registry. */
+       if (registry->metadata_key) {
+               ret = 0;
+               goto error;
        }
 
        /* Allocate UST metadata */
@@ -1795,30 +2522,56 @@ static int create_ust_app_metadata(struct ust_app_session *ua_sess,
                goto error;
        }
 
-       /* Set default attributes for metadata. */
-       metadata->attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
-       metadata->attr.subbuf_size = default_get_metadata_subbuf_size();
-       metadata->attr.num_subbuf = DEFAULT_METADATA_SUBBUF_NUM;
-       metadata->attr.switch_timer_interval = DEFAULT_UST_CHANNEL_SWITCH_TIMER;
-       metadata->attr.read_timer_interval = DEFAULT_UST_CHANNEL_READ_TIMER;
-       metadata->attr.output = LTTNG_UST_MMAP;
-       metadata->attr.type = LTTNG_UST_CHAN_METADATA;
+       if (!attr) {
+               /* Set default attributes for metadata. */
+               metadata->attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
+               metadata->attr.subbuf_size = default_get_metadata_subbuf_size();
+               metadata->attr.num_subbuf = DEFAULT_METADATA_SUBBUF_NUM;
+               metadata->attr.switch_timer_interval = DEFAULT_METADATA_SWITCH_TIMER;
+               metadata->attr.read_timer_interval = DEFAULT_METADATA_READ_TIMER;
+               metadata->attr.output = LTTNG_UST_MMAP;
+               metadata->attr.type = LTTNG_UST_CHAN_METADATA;
+       } else {
+               memcpy(&metadata->attr, attr, sizeof(metadata->attr));
+               metadata->attr.output = LTTNG_UST_MMAP;
+               metadata->attr.type = LTTNG_UST_CHAN_METADATA;
+       }
+
+       /* Need one fd for the channel. */
+       ret = lttng_fd_get(LTTNG_FD_APPS, 1);
+       if (ret < 0) {
+               ERR("Exhausted number of available FD upon create metadata");
+               goto error;
+       }
 
        /* Get the right consumer socket for the application. */
-       socket = find_consumer_socket_by_bitness(app->bits_per_long, consumer);
+       socket = consumer_find_socket_by_bitness(app->bits_per_long, consumer);
        if (!socket) {
                ret = -EINVAL;
                goto error_consumer;
        }
 
+       /*
+        * Keep metadata key so we can identify it on the consumer side. Assign it
+        * to the registry *before* we ask the consumer so we avoid the race of the
+        * consumer requesting the metadata and the ask_channel call on our side
+        * did not returned yet.
+        */
+       registry->metadata_key = metadata->key;
+
        /*
         * Ask the metadata channel creation to the consumer. The metadata object
         * will be created by the consumer and kept their. However, the stream is
         * never added or monitored until we do a first push metadata to the
         * consumer.
         */
-       ret = ust_consumer_ask_channel(ua_sess, metadata, consumer, socket);
+       ret = ust_consumer_ask_channel(ua_sess, metadata, consumer, socket,
+                       registry);
        if (ret < 0) {
+               /*
+                * Safe because the metadata obj pointer is not set so the delete below
+                * will not put a FD back again.
+                */
                goto error_consumer;
        }
 
@@ -1828,18 +2581,20 @@ static int create_ust_app_metadata(struct ust_app_session *ua_sess,
         * because after this point, if an error occurs, the only way the stream
         * can be deleted is to be monitored in the consumer.
         */
-       ret = ust_consumer_setup_metadata(socket, metadata);
+       ret = consumer_setup_metadata(socket, metadata->key);
        if (ret < 0) {
+               /*
+                * Safe because the metadata obj pointer is not set so the delete below
+                * will not put a FD back again.
+                */
                goto error_consumer;
        }
 
-       ua_sess->metadata = metadata;
+       DBG2("UST metadata with key %" PRIu64 " created for app pid %d",
+                       metadata->key, app->pid);
 
-       DBG2("UST metadata created for app pid %d", app->pid);
-
-end:
-       return 0;
 error_consumer:
+       lttng_fd_put(LTTNG_FD_APPS, 1);
        delete_ust_app_channel(-1, metadata, app);
 error:
        return ret;
@@ -2061,6 +2816,8 @@ void ust_app_unregister(int sock)
        /* Remove sessions so they are not visible during deletion.*/
        cds_lfht_for_each_entry(lta->sessions->ht, &iter.iter, ua_sess,
                        node.node) {
+               struct ust_registry_session *registry;
+
                ret = lttng_ht_del(lta->sessions, &iter);
                if (ret) {
                        /* The session was already removed so scheduled for teardown. */
@@ -2084,8 +2841,20 @@ void ust_app_unregister(int sock)
                 * The close metadata below nullifies the metadata pointer in the
                 * session so the delete session will NOT push/close a second time.
                 */
-               (void) push_metadata(lta, ua_sess);
-               (void) close_metadata(lta, ua_sess);
+               registry = get_session_registry(ua_sess);
+               if (registry) {
+                       /* Push metadata for application before freeing the application. */
+                       (void) push_metadata(registry, ua_sess->consumer);
+
+                       /*
+                        * Don't ask to close metadata for global per UID buffers. Close
+                        * metadata only on destroy trace session in this case.
+                        */
+                       if (ua_sess->buffer_type != LTTNG_BUFFER_PER_UID) {
+                               /* And ask to close it for this session registry. */
+                               (void) close_metadata(registry, ua_sess->consumer);
+                       }
+               }
 
                cds_list_add(&ua_sess->teardown_node, &lta->teardown_head);
                pthread_mutex_unlock(&ua_sess->lock);
@@ -2307,6 +3076,8 @@ error:
 
 /*
  * Free and clean all traceable apps of the global list.
+ *
+ * Should _NOT_ be called with RCU read-side lock held.
  */
 void ust_app_clean_list(void)
 {
@@ -2337,13 +3108,12 @@ void ust_app_clean_list(void)
                ret = lttng_ht_del(ust_app_ht_by_notify_sock, &iter);
                assert(!ret);
        }
+       rcu_read_unlock();
 
        /* Destroy is done only when the ht is empty */
        lttng_ht_destroy(ust_app_ht);
        lttng_ht_destroy(ust_app_ht_by_sock);
        lttng_ht_destroy(ust_app_ht_by_notify_sock);
-
-       rcu_read_unlock();
 }
 
 /*
@@ -2608,7 +3378,7 @@ int ust_app_create_channel_glb(struct ltt_ust_session *usess,
        assert(usess);
        assert(uchan);
 
-       DBG2("UST app adding channel %s to global domain for session id %d",
+       DBG2("UST app adding channel %s to UST domain for session id %d",
                        uchan->name, usess->id);
 
        rcu_read_lock();
@@ -2645,9 +3415,17 @@ int ust_app_create_channel_glb(struct ltt_ust_session *usess,
                assert(ua_sess);
 
                pthread_mutex_lock(&ua_sess->lock);
-               /* Create channel onto application. We don't need the chan ref. */
-               ret = create_ust_app_channel(ua_sess, uchan, app, usess->consumer,
-                               LTTNG_UST_CHAN_PER_CPU, NULL);
+               if (!strncmp(uchan->name, DEFAULT_METADATA_NAME,
+                                       sizeof(uchan->name))) {
+                       struct ustctl_consumer_channel_attr attr;
+                       copy_channel_attr_to_ustctl(&attr, &uchan->attr);
+                       ret = create_ust_app_metadata(ua_sess, app, usess->consumer,
+                                       &attr);
+               } else {
+                       /* Create channel onto application. We don't need the chan ref. */
+                       ret = create_ust_app_channel(ua_sess, uchan, app,
+                                       LTTNG_UST_CHAN_PER_CPU, usess, NULL);
+               }
                pthread_mutex_unlock(&ua_sess->lock);
                if (ret < 0) {
                        if (ret == -ENOMEM) {
@@ -2803,6 +3581,7 @@ int ust_app_create_event_glb(struct ltt_ust_session *usess,
 /*
  * Start tracing for a specific UST session and app.
  */
+static
 int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
 {
        int ret = 0;
@@ -2833,7 +3612,7 @@ int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
        if (usess->consumer->type == CONSUMER_DST_LOCAL &&
                        strlen(usess->consumer->dst.trace_path) > 0) {
                ret = run_as_mkdir_recursive(usess->consumer->dst.trace_path,
-                               S_IRWXU | S_IRWXG, usess->uid, usess->gid);
+                               S_IRWXU | S_IRWXG, ua_sess->euid, ua_sess->egid);
                if (ret < 0) {
                        if (ret != -EEXIST) {
                                ERR("Trace directory creation error");
@@ -2842,8 +3621,11 @@ int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
                }
        }
 
-       /* Create the metadata for the application. */
-       ret = create_ust_app_metadata(ua_sess, app, usess->consumer);
+       /*
+        * Create the metadata for the application. This returns gracefully if a
+        * metadata was already set for the session.
+        */
+       ret = create_ust_app_metadata(ua_sess, app, usess->consumer, NULL);
        if (ret < 0) {
                goto error_unlock;
        }
@@ -2892,12 +3674,12 @@ error_unlock:
 /*
  * Stop tracing for a specific UST session and app.
  */
+static
 int ust_app_stop_trace(struct ltt_ust_session *usess, struct ust_app *app)
 {
        int ret = 0;
-       struct lttng_ht_iter iter;
        struct ust_app_session *ua_sess;
-       struct ust_app_channel *ua_chan;
+       struct ust_registry_session *registry;
 
        DBG("Stopping tracing for ust app pid %d", app->pid);
 
@@ -2949,6 +3731,52 @@ int ust_app_stop_trace(struct ltt_ust_session *usess, struct ust_app *app)
 
        health_code_update();
 
+       registry = get_session_registry(ua_sess);
+       assert(registry);
+       /* Push metadata for application before freeing the application. */
+       (void) push_metadata(registry, ua_sess->consumer);
+
+       pthread_mutex_unlock(&ua_sess->lock);
+end_no_session:
+       rcu_read_unlock();
+       health_code_update();
+       return 0;
+
+error_rcu_unlock:
+       pthread_mutex_unlock(&ua_sess->lock);
+       rcu_read_unlock();
+       health_code_update();
+       return -1;
+}
+
+/*
+ * Flush buffers for a specific UST session and app.
+ */
+static
+int ust_app_flush_trace(struct ltt_ust_session *usess, struct ust_app *app)
+{
+       int ret = 0;
+       struct lttng_ht_iter iter;
+       struct ust_app_session *ua_sess;
+       struct ust_app_channel *ua_chan;
+
+       DBG("Flushing buffers for ust app pid %d", app->pid);
+
+       rcu_read_lock();
+
+       if (!app->compatible) {
+               goto end_no_session;
+       }
+
+       ua_sess = lookup_session_by_app(usess, app);
+       if (ua_sess == NULL) {
+               goto end_no_session;
+       }
+
+       pthread_mutex_lock(&ua_sess->lock);
+
+       health_code_update();
+
        /* Flushing buffers */
        cds_lfht_for_each_entry(ua_sess->channels->ht, &iter.iter, ua_chan,
                        node.node) {
@@ -2972,22 +3800,11 @@ int ust_app_stop_trace(struct ltt_ust_session *usess, struct ust_app *app)
 
        health_code_update();
 
-       ret = push_metadata(app, ua_sess);
-       if (ret < 0) {
-               goto error_rcu_unlock;
-       }
-
        pthread_mutex_unlock(&ua_sess->lock);
 end_no_session:
        rcu_read_unlock();
        health_code_update();
        return 0;
-
-error_rcu_unlock:
-       pthread_mutex_unlock(&ua_sess->lock);
-       rcu_read_unlock();
-       health_code_update();
-       return -1;
 }
 
 /*
@@ -3075,12 +3892,56 @@ int ust_app_stop_trace_all(struct ltt_ust_session *usess)
        cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                ret = ust_app_stop_trace(usess, app);
                if (ret < 0) {
-                       ERR("UST app stop trace failed with ret %d", ret);
                        /* Continue to next apps even on error */
                        continue;
                }
        }
 
+       /* Flush buffers */
+       switch (usess->buffer_type) {
+       case LTTNG_BUFFER_PER_UID:
+       {
+               struct buffer_reg_uid *reg;
+
+               /* Flush all per UID buffers associated to that session. */
+               cds_list_for_each_entry(reg, &usess->buffer_reg_uid_list, lnode) {
+                       struct buffer_reg_channel *reg_chan;
+                       struct consumer_socket *socket;
+
+                       /* Get consumer socket to use to push the metadata.*/
+                       socket = consumer_find_socket_by_bitness(reg->bits_per_long,
+                                       usess->consumer);
+                       if (!socket) {
+                               /* Ignore request if no consumer is found for the session. */
+                               continue;
+                       }
+
+                       cds_lfht_for_each_entry(reg->registry->channels->ht, &iter.iter,
+                                       reg_chan, node.node) {
+                               /*
+                                * The following call will print error values so the return
+                                * code is of little importance because whatever happens, we
+                                * have to try them all.
+                                */
+                               (void) consumer_flush_channel(socket, reg_chan->consumer_key);
+                       }
+               }
+               break;
+       }
+       case LTTNG_BUFFER_PER_PID:
+               cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
+                       ret = ust_app_flush_trace(usess, app);
+                       if (ret < 0) {
+                               /* Continue to next apps even on error */
+                               continue;
+                       }
+               }
+               break;
+       default:
+               assert(0);
+               break;
+       }
+
        rcu_read_unlock();
 
        return 0;
@@ -3163,14 +4024,31 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
         */
        cds_lfht_for_each_entry(ua_sess->channels->ht, &iter.iter, ua_chan,
                        node.node) {
-               ret = create_ust_channel(app, ua_sess, ua_chan, usess->consumer);
-               if (ret < 0) {
-                       /*
-                        * Stop everything. On error, the application failed, no more file
-                        * descriptor are available or ENOMEM so stopping here is the only
-                        * thing we can do for now.
-                        */
-                       goto error_unlock;
+               /*
+                * For a metadata channel, handle it differently.
+                */
+               if (!strncmp(ua_chan->name, DEFAULT_METADATA_NAME,
+                                       sizeof(ua_chan->name))) {
+                       ret = create_ust_app_metadata(ua_sess, app, usess->consumer,
+                                       &ua_chan->attr);
+                       if (ret < 0) {
+                               goto error_unlock;
+                       }
+                       /* Remove it from the hash table and continue!. */
+                       ret = lttng_ht_del(ua_sess->channels, &iter);
+                       assert(!ret);
+                       delete_ust_app_channel(-1, ua_chan, app);
+                       continue;
+               } else {
+                       ret = do_create_channel(app, usess, ua_sess, ua_chan);
+                       if (ret < 0) {
+                               /*
+                                * Stop everything. On error, the application failed, no more
+                                * file descriptor are available or ENOMEM so stopping here is
+                                * the only thing we can do for now.
+                                */
+                               goto error_unlock;
+                       }
                }
 
                cds_lfht_for_each_entry(ua_chan->ctx->ht, &iter_ctx.iter, ua_ctx,
@@ -3531,10 +4409,13 @@ static int reply_ust_register_channel(int sock, int sobjd, int cobjd,
 {
        int ret, ret_code = 0;
        uint32_t chan_id, reg_count;
+       uint64_t chan_reg_key;
        enum ustctl_channel_header type;
        struct ust_app *app;
        struct ust_app_channel *ua_chan;
        struct ust_app_session *ua_sess;
+       struct ust_registry_session *registry;
+       struct ust_registry_channel *chan_reg;
 
        rcu_read_lock();
 
@@ -3552,40 +4433,44 @@ static int reply_ust_register_channel(int sock, int sobjd, int cobjd,
        assert(ua_chan);
        assert(ua_chan->session);
        ua_sess = ua_chan->session;
-       assert(ua_sess);
-
-       pthread_mutex_lock(&ua_sess->registry.lock);
 
-       if (ust_registry_is_max_id(ua_chan->session->registry.used_channel_id)) {
-               ret_code = -1;
-               chan_id = -1U;
-               type = -1;
-               goto reply;
-       }
+       /* Get right session registry depending on the session buffer type. */
+       registry = get_session_registry(ua_sess);
+       assert(registry);
 
-       /* Don't assign ID to metadata. */
-       if (ua_chan->attr.type == LTTNG_UST_CHAN_METADATA) {
-               chan_id = -1U;
+       /* Depending on the buffer type, a different channel key is used. */
+       if (ua_sess->buffer_type == LTTNG_BUFFER_PER_UID) {
+               chan_reg_key = ua_chan->tracing_channel_id;
        } else {
-               chan_id = ust_registry_get_next_chan_id(&ua_chan->session->registry);
+               chan_reg_key = ua_chan->key;
        }
 
-       reg_count = ust_registry_get_event_count(&ua_chan->registry);
-       if (reg_count < 31) {
-               type = USTCTL_CHANNEL_HEADER_COMPACT;
+       pthread_mutex_lock(&registry->lock);
+
+       chan_reg = ust_registry_channel_find(registry, chan_reg_key);
+       assert(chan_reg);
+
+       if (!chan_reg->register_done) {
+               reg_count = ust_registry_get_event_count(chan_reg);
+               if (reg_count < 31) {
+                       type = USTCTL_CHANNEL_HEADER_COMPACT;
+               } else {
+                       type = USTCTL_CHANNEL_HEADER_LARGE;
+               }
+
+               chan_reg->nr_ctx_fields = nr_fields;
+               chan_reg->ctx_fields = fields;
+               chan_reg->header_type = type;
        } else {
-               type = USTCTL_CHANNEL_HEADER_LARGE;
+               /* Get current already assigned values. */
+               type = chan_reg->header_type;
        }
-
-       ua_chan->registry.nr_ctx_fields = nr_fields;
-       ua_chan->registry.ctx_fields = fields;
-       ua_chan->registry.chan_id = chan_id;
-       ua_chan->registry.header_type = type;
+       /* Channel id is set during the object creation. */
+       chan_id = chan_reg->chan_id;
 
        /* Append to metadata */
-       if (!ret_code) {
-               ret_code = ust_metadata_channel_statedump(&ua_chan->session->registry,
-                               &ua_chan->registry);
+       if (!chan_reg->metadata_dumped) {
+               ret_code = ust_metadata_channel_statedump(registry, chan_reg);
                if (ret_code) {
                        ERR("Error appending channel metadata (errno = %d)", ret_code);
                        goto reply;
@@ -3593,8 +4478,9 @@ static int reply_ust_register_channel(int sock, int sobjd, int cobjd,
        }
 
 reply:
-       DBG3("UST app replying to register channel with id %u, type: %d, ret: %d",
-                       chan_id, type, ret_code);
+       DBG3("UST app replying to register channel key %" PRIu64
+                       " with id %u, type: %d, ret: %d", chan_reg_key, chan_id, type,
+                       ret_code);
 
        ret = ustctl_reply_register_channel(sock, chan_id, type, ret_code);
        if (ret < 0) {
@@ -3606,8 +4492,11 @@ reply:
                goto error;
        }
 
+       /* This channel registry registration is completed. */
+       chan_reg->register_done = 1;
+
 error:
-       pthread_mutex_unlock(&ua_sess->registry.lock);
+       pthread_mutex_unlock(&registry->lock);
 error_rcu_unlock:
        rcu_read_unlock();
        return ret;
@@ -3628,9 +4517,11 @@ static int add_event_ust_registry(int sock, int sobjd, int cobjd, char *name,
 {
        int ret, ret_code;
        uint32_t event_id = 0;
+       uint64_t chan_reg_key;
        struct ust_app *app;
        struct ust_app_channel *ua_chan;
        struct ust_app_session *ua_sess;
+       struct ust_registry_session *registry;
 
        rcu_read_lock();
 
@@ -3649,11 +4540,20 @@ static int add_event_ust_registry(int sock, int sobjd, int cobjd, char *name,
        assert(ua_chan->session);
        ua_sess = ua_chan->session;
 
-       pthread_mutex_lock(&ua_sess->registry.lock);
+       registry = get_session_registry(ua_sess);
+       assert(registry);
+
+       if (ua_sess->buffer_type == LTTNG_BUFFER_PER_UID) {
+               chan_reg_key = ua_chan->tracing_channel_id;
+       } else {
+               chan_reg_key = ua_chan->key;
+       }
+
+       pthread_mutex_lock(&registry->lock);
 
-       ret_code = ust_registry_create_event(&ua_sess->registry,
-                       &ua_chan->registry, sobjd, cobjd, name, sig, nr_fields, fields,
-                       loglevel, model_emf_uri, &event_id);
+       ret_code = ust_registry_create_event(registry, chan_reg_key,
+                       sobjd, cobjd, name, sig, nr_fields, fields, loglevel,
+                       model_emf_uri, ua_sess->buffer_type, &event_id);
 
        /*
         * The return value is returned to ustctl so in case of an error, the
@@ -3674,10 +4574,11 @@ static int add_event_ust_registry(int sock, int sobjd, int cobjd, char *name,
                goto error;
        }
 
-       DBG3("UST registry event %s has been added successfully", name);
+       DBG3("UST registry event %s with id %" PRId32 " added successfully",
+                       name, event_id);
 
 error:
-       pthread_mutex_unlock(&ua_sess->registry.lock);
+       pthread_mutex_unlock(&registry->lock);
 error_rcu_unlock:
        rcu_read_unlock();
        return ret;
This page took 0.049769 seconds and 4 git commands to generate.