Fix: rotation_unavailable returned on failure to read time
[lttng-tools.git] / src / bin / lttng-sessiond / cmd.c
index e0a8db9b2cc13a2b5c77407e0b14938fa565a587..1ac133f3606d68d3114bb6405f103d89f30851ea 100644 (file)
@@ -21,6 +21,7 @@
 #include <inttypes.h>
 #include <urcu/list.h>
 #include <urcu/uatomic.h>
+#include <sys/stat.h>
 
 #include <common/defaults.h>
 #include <common/common.h>
@@ -37,6 +38,8 @@
 #include <lttng/channel.h>
 #include <lttng/channel-internal.h>
 #include <lttng/rotate-internal.h>
+#include <lttng/location-internal.h>
+#include <lttng/userspace-probe-internal.h>
 #include <common/string-utils/string-utils.h>
 
 #include "channel.h"
 #include "kernel-consumer.h"
 #include "lttng-sessiond.h"
 #include "utils.h"
-#include "syscall.h"
+#include "lttng-syscall.h"
 #include "agent.h"
 #include "buffer-registry.h"
 #include "notification-thread.h"
 #include "notification-thread-commands.h"
 #include "rotate.h"
 #include "rotation-thread.h"
-#include "sessiond-timer.h"
+#include "timer.h"
+#include "agent-thread.h"
 
 #include "cmd.h"
 
+/* Sleep for 100ms between each check for the shm path's deletion. */
+#define SESSION_DESTROY_SHM_PATH_CHECK_DELAY_US 100000
+
+static enum lttng_error_code wait_on_path(void *path);
+
+/*
+ * Command completion handler that is used by the destroy command
+ * when a session that has a non-default shm_path is being destroyed.
+ *
+ * See comment in cmd_destroy_session() for the rationale.
+ */
+static struct destroy_completion_handler {
+       struct cmd_completion_handler handler;
+       char shm_path[member_sizeof(struct ltt_session, shm_path)];
+} destroy_completion_handler = {
+       .handler = {
+               .run = wait_on_path,
+               .data = destroy_completion_handler.shm_path
+       },
+       .shm_path = { 0 },
+};
+
+static struct cmd_completion_handler *current_completion_handler;
+
 /*
  * Used to keep a unique index for each relayd socket created where this value
  * is associated with streams on the consumer so it can match the right relayd
@@ -357,9 +385,13 @@ end:
        }
 }
 
-static void increment_extended_len(const char *filter_expression,
-               struct lttng_event_exclusion *exclusion, size_t *extended_len)
+static int increment_extended_len(const char *filter_expression,
+               struct lttng_event_exclusion *exclusion,
+               const struct lttng_userspace_probe_location *probe_location,
+               size_t *extended_len)
 {
+       int ret = 0;
+
        *extended_len += sizeof(struct lttcomm_event_extended_header);
 
        if (filter_expression) {
@@ -369,14 +401,31 @@ static void increment_extended_len(const char *filter_expression,
        if (exclusion) {
                *extended_len += exclusion->count * LTTNG_SYMBOL_NAME_LEN;
        }
+
+       if (probe_location) {
+               ret = lttng_userspace_probe_location_serialize(probe_location,
+                               NULL, NULL);
+               if (ret < 0) {
+                       goto end;
+               }
+               *extended_len += ret;
+       }
+       ret = 0;
+end:
+       return ret;
 }
 
-static void append_extended_info(const char *filter_expression,
-               struct lttng_event_exclusion *exclusion, void **extended_at)
+static int append_extended_info(const char *filter_expression,
+               struct lttng_event_exclusion *exclusion,
+               struct lttng_userspace_probe_location *probe_location,
+               void **extended_at)
 {
-       struct lttcomm_event_extended_header extended_header;
+       int ret = 0;
        size_t filter_len = 0;
        size_t nb_exclusions = 0;
+       size_t userspace_probe_location_len = 0;
+       struct lttng_dynamic_buffer location_buffer;
+       struct lttcomm_event_extended_header extended_header;
 
        if (filter_expression) {
                filter_len = strlen(filter_expression) + 1;
@@ -386,9 +435,21 @@ static void append_extended_info(const char *filter_expression,
                nb_exclusions = exclusion->count;
        }
 
+       if (probe_location) {
+               lttng_dynamic_buffer_init(&location_buffer);
+               ret = lttng_userspace_probe_location_serialize(probe_location,
+                               &location_buffer, NULL);
+               if (ret < 0) {
+                       ret = -1;
+                       goto end;
+               }
+               userspace_probe_location_len = location_buffer.size;
+       }
+
        /* Set header fields */
        extended_header.filter_len = filter_len;
        extended_header.nb_exclusions = nb_exclusions;
+       extended_header.userspace_probe_location_len = userspace_probe_location_len;
 
        /* Copy header */
        memcpy(*extended_at, &extended_header, sizeof(extended_header));
@@ -407,6 +468,15 @@ static void append_extended_info(const char *filter_expression,
                memcpy(*extended_at, &exclusion->names, len);
                *extended_at += len;
        }
+
+       if (probe_location) {
+               memcpy(*extended_at, location_buffer.data, location_buffer.size);
+               *extended_at += location_buffer.size;
+               lttng_dynamic_buffer_reset(&location_buffer);
+       }
+       ret = 0;
+end:
+       return ret;
 }
 
 /*
@@ -420,7 +490,7 @@ static int list_lttng_agent_events(struct agent *agt,
        int i = 0, ret = 0;
        unsigned int nb_event = 0;
        struct agent_event *event;
-       struct lttng_event *tmp_events;
+       struct lttng_event *tmp_events = NULL;
        struct lttng_ht_iter iter;
        size_t extended_len = 0;
        void *extended_at;
@@ -448,8 +518,13 @@ static int list_lttng_agent_events(struct agent *agt,
         */
        rcu_read_lock();
        cds_lfht_for_each_entry(agt->events->ht, &iter.iter, event, node.node) {
-               increment_extended_len(event->filter_expression, NULL,
+               ret = increment_extended_len(event->filter_expression, NULL, NULL,
                                &extended_len);
+               if (ret) {
+                       DBG("Error computing the length of extended info message");
+                       ret = -LTTNG_ERR_FATAL;
+                       goto error;
+               }
        }
        rcu_read_unlock();
 
@@ -474,17 +549,25 @@ static int list_lttng_agent_events(struct agent *agt,
                i++;
 
                /* Append extended info */
-               append_extended_info(event->filter_expression, NULL,
+               ret = append_extended_info(event->filter_expression, NULL, NULL,
                                &extended_at);
+               if (ret) {
+                       DBG("Error appending extended info message");
+                       ret = -LTTNG_ERR_FATAL;
+                       goto error;
+               }
        }
-       rcu_read_unlock();
 
        *events = tmp_events;
        ret = nb_event;
-
-error:
        assert(nb_event == i);
+
+end:
+       rcu_read_unlock();
        return ret;
+error:
+       free(tmp_events);
+       goto end;
 }
 
 /*
@@ -533,8 +616,13 @@ static int list_lttng_ust_global_events(char *channel_name,
                        continue;
                }
 
-               increment_extended_len(uevent->filter_expression,
-                       uevent->exclusion, &extended_len);
+               ret = increment_extended_len(uevent->filter_expression,
+                       uevent->exclusion, NULL, &extended_len);
+               if (ret) {
+                       DBG("Error computing the length of extended info message");
+                       ret = -LTTNG_ERR_FATAL;
+                       goto end;
+               }
        }
        if (nb_event == 0) {
                /* All events are internal, skip. */
@@ -594,8 +682,13 @@ static int list_lttng_ust_global_events(char *channel_name,
                i++;
 
                /* Append extended info */
-               append_extended_info(uevent->filter_expression,
-                       uevent->exclusion, &extended_at);
+               ret = append_extended_info(uevent->filter_expression,
+                       uevent->exclusion, NULL, &extended_at);
+               if (ret) {
+                       DBG("Error appending extended info message");
+                       ret = -LTTNG_ERR_FATAL;
+                       goto end;
+               }
        }
 
        ret = nb_event;
@@ -637,14 +730,20 @@ static int list_lttng_kernel_events(char *channel_name,
 
        /* Compute required extended infos size */
        cds_list_for_each_entry(event, &kchan->events_list.head, list) {
-               increment_extended_len(event->filter_expression, NULL,
+               ret = increment_extended_len(event->filter_expression, NULL,
+                       event->userspace_probe_location,
                        &extended_len);
+               if (ret) {
+                       DBG("Error computing the length of extended info message");
+                       ret = -LTTNG_ERR_FATAL;
+                       goto error;
+               }
        }
 
        *total_size = nb_event * sizeof(struct lttng_event) + extended_len;
        *events = zmalloc(*total_size);
        if (*events == NULL) {
-               ret = LTTNG_ERR_FATAL;
+               ret = -LTTNG_ERR_FATAL;
                goto error;
        }
 
@@ -673,6 +772,9 @@ static int list_lttng_kernel_events(char *channel_name,
                        memcpy(&(*events)[i].attr.probe, &event->event->u.kprobe,
                                        sizeof(struct lttng_kernel_kprobe));
                        break;
+               case LTTNG_KERNEL_UPROBE:
+                       (*events)[i].type = LTTNG_EVENT_USERSPACE_PROBE;
+                       break;
                case LTTNG_KERNEL_FUNCTION:
                        (*events)[i].type = LTTNG_EVENT_FUNCTION;
                        memcpy(&((*events)[i].attr.ftrace), &event->event->u.ftrace,
@@ -685,14 +787,21 @@ static int list_lttng_kernel_events(char *channel_name,
                        (*events)[i].type = LTTNG_EVENT_SYSCALL;
                        break;
                case LTTNG_KERNEL_ALL:
+                       /* fall-through. */
+               default:
                        assert(0);
                        break;
                }
                i++;
 
                /* Append extended info */
-               append_extended_info(event->filter_expression, NULL,
-                       &extended_at);
+               ret = append_extended_info(event->filter_expression, NULL,
+                       event->userspace_probe_location, &extended_at);
+               if (ret) {
+                       DBG("Error appending extended info message");
+                       ret = -LTTNG_ERR_FATAL;
+                       goto error;
+               }
        }
 
 end:
@@ -845,19 +954,20 @@ error:
  * Create a socket to the relayd using the URI.
  *
  * On success, the relayd_sock pointer is set to the created socket.
- * Else, it's stays untouched and a lttcomm error code is returned.
+ * Else, it remains untouched and an LTTng error code is returned.
  */
-static int create_connect_relayd(struct lttng_uri *uri,
+static enum lttng_error_code create_connect_relayd(struct lttng_uri *uri,
                struct lttcomm_relayd_sock **relayd_sock,
                struct consumer_output *consumer)
 {
        int ret;
+       enum lttng_error_code status = LTTNG_OK;
        struct lttcomm_relayd_sock *rsock;
 
        rsock = lttcomm_alloc_relayd_sock(uri, RELAYD_VERSION_COMM_MAJOR,
                        RELAYD_VERSION_COMM_MINOR);
        if (!rsock) {
-               ret = LTTNG_ERR_FATAL;
+               status = LTTNG_ERR_FATAL;
                goto error;
        }
 
@@ -871,7 +981,7 @@ static int create_connect_relayd(struct lttng_uri *uri,
        health_poll_exit();
        if (ret < 0) {
                ERR("Unable to reach lttng-relayd");
-               ret = LTTNG_ERR_RELAYD_CONNECT_FAIL;
+               status = LTTNG_ERR_RELAYD_CONNECT_FAIL;
                goto free_sock;
        }
 
@@ -882,10 +992,11 @@ static int create_connect_relayd(struct lttng_uri *uri,
                /* Check relayd version */
                ret = relayd_version_check(rsock);
                if (ret == LTTNG_ERR_RELAYD_VERSION_FAIL) {
+                       status = LTTNG_ERR_RELAYD_VERSION_FAIL;
                        goto close_sock;
                } else if (ret < 0) {
                        ERR("Unable to reach lttng-relayd");
-                       ret = LTTNG_ERR_RELAYD_CONNECT_FAIL;
+                       status = LTTNG_ERR_RELAYD_CONNECT_FAIL;
                        goto close_sock;
                }
                consumer->relay_major_version = rsock->major;
@@ -895,13 +1006,13 @@ static int create_connect_relayd(struct lttng_uri *uri,
        } else {
                /* Command is not valid */
                ERR("Relayd invalid stream type: %d", uri->stype);
-               ret = LTTNG_ERR_INVALID;
+               status = LTTNG_ERR_INVALID;
                goto close_sock;
        }
 
        *relayd_sock = rsock;
 
-       return LTTNG_OK;
+       return status;
 
 close_sock:
        /* The returned value is not useful since we are on an error path. */
@@ -909,26 +1020,30 @@ close_sock:
 free_sock:
        free(rsock);
 error:
-       return ret;
+       return status;
 }
 
 /*
  * Connect to the relayd using URI and send the socket to the right consumer.
  *
  * The consumer socket lock must be held by the caller.
+ *
+ * Returns LTTNG_OK on success or an LTTng error code on failure.
  */
-static int send_consumer_relayd_socket(enum lttng_domain_type domain,
-               unsigned int session_id, struct lttng_uri *relayd_uri,
+static enum lttng_error_code send_consumer_relayd_socket(
+               unsigned int session_id,
+               struct lttng_uri *relayd_uri,
                struct consumer_output *consumer,
                struct consumer_socket *consumer_sock,
                char *session_name, char *hostname, int session_live_timer)
 {
        int ret;
        struct lttcomm_relayd_sock *rsock = NULL;
+       enum lttng_error_code status;
 
        /* Connect to relayd and make version check if uri is the control. */
-       ret = create_connect_relayd(relayd_uri, &rsock, consumer);
-       if (ret != LTTNG_OK) {
+       status = create_connect_relayd(relayd_uri, &rsock, consumer);
+       if (status != LTTNG_OK) {
                goto relayd_comm_error;
        }
        assert(rsock);
@@ -950,7 +1065,7 @@ static int send_consumer_relayd_socket(enum lttng_domain_type domain,
                        relayd_uri->stype, session_id,
                        session_name, hostname, session_live_timer);
        if (ret < 0) {
-               ret = LTTNG_ERR_ENABLE_CONSUMER_FAIL;
+               status = LTTNG_ERR_ENABLE_CONSUMER_FAIL;
                goto close_sock;
        }
 
@@ -961,15 +1076,13 @@ static int send_consumer_relayd_socket(enum lttng_domain_type domain,
                consumer_sock->data_sock_sent = 1;
        }
 
-       ret = LTTNG_OK;
-
        /*
         * Close socket which was dup on the consumer side. The session daemon does
         * NOT keep track of the relayd socket(s) once transfer to the consumer.
         */
 
 close_sock:
-       if (ret != LTTNG_OK) {
+       if (status != LTTNG_OK) {
                /*
                 * The consumer output for this session should not be used anymore
                 * since the relayd connection failed thus making any tracing or/and
@@ -981,7 +1094,7 @@ close_sock:
        free(rsock);
 
 relayd_comm_error:
-       return ret;
+       return status;
 }
 
 /*
@@ -990,39 +1103,42 @@ relayd_comm_error:
  * session.
  *
  * The consumer socket lock must be held by the caller.
+ *
+ * Returns LTTNG_OK, or an LTTng error code on failure.
  */
-static int send_consumer_relayd_sockets(enum lttng_domain_type domain,
+static enum lttng_error_code 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;
+       enum lttng_error_code status = LTTNG_OK;
 
        assert(consumer);
        assert(sock);
 
        /* Sending control relayd socket. */
        if (!sock->control_sock_sent) {
-               ret = send_consumer_relayd_socket(domain, session_id,
+               status = send_consumer_relayd_socket(session_id,
                                &consumer->dst.net.control, consumer, sock,
                                session_name, hostname, session_live_timer);
-               if (ret != LTTNG_OK) {
+               if (status != LTTNG_OK) {
                        goto error;
                }
        }
 
        /* Sending data relayd socket. */
        if (!sock->data_sock_sent) {
-               ret = send_consumer_relayd_socket(domain, session_id,
+               status = send_consumer_relayd_socket(session_id,
                                &consumer->dst.net.data, consumer, sock,
                                session_name, hostname, session_live_timer);
-               if (ret != LTTNG_OK) {
+               if (status != LTTNG_OK) {
                        goto error;
                }
        }
 
 error:
-       return ret;
+       return status;
 }
 
 /*
@@ -1152,7 +1268,7 @@ static int start_kernel_session(struct ltt_kernel_session *ksess, int wpipe)
        }
 
        /* Quiescent wait after starting trace */
-       kernel_wait_quiescent(kernel_tracer_fd);
+       kernel_wait_quiescent(wpipe);
 
        ksess->active = 1;
 
@@ -1384,9 +1500,15 @@ int cmd_enable_channel(struct ltt_session *session,
                break;
        }
        case LTTNG_DOMAIN_UST:
+               break;
        case LTTNG_DOMAIN_JUL:
        case LTTNG_DOMAIN_LOG4J:
        case LTTNG_DOMAIN_PYTHON:
+               if (!agent_tracing_is_enabled()) {
+                       DBG("Attempted to enable a channel in an agent domain but the agent thread is not running");
+                       ret = LTTNG_ERR_AGENT_TRACING_DISABLED;
+                       goto error;
+               }
                break;
        default:
                ret = LTTNG_ERR_UNKNOWN_DOMAIN;
@@ -1963,6 +2085,7 @@ static int _cmd_enable_event(struct ltt_session *session,
                        break;
                }
                case LTTNG_EVENT_PROBE:
+               case LTTNG_EVENT_USERSPACE_PROBE:
                case LTTNG_EVENT_FUNCTION:
                case LTTNG_EVENT_FUNCTION_ENTRY:
                case LTTNG_EVENT_TRACEPOINT:
@@ -2060,8 +2183,7 @@ static int _cmd_enable_event(struct ltt_session *session,
                        ret = validate_ust_event_name(event->name);
                        if (ret) {
                                WARN("Userspace event name %s failed validation.",
-                                               event->name ?
-                                               event->name : "NULL");
+                                               event->name);
                                ret = LTTNG_ERR_INVALID_EVENT_NAME;
                                goto error;
                        }
@@ -2094,6 +2216,12 @@ static int _cmd_enable_event(struct ltt_session *session,
 
                assert(usess);
 
+               if (!agent_tracing_is_enabled()) {
+                       DBG("Attempted to enable an event in an agent domain but the agent thread is not running");
+                       ret = LTTNG_ERR_AGENT_TRACING_DISABLED;
+                       goto error;
+               }
+
                agt = trace_ust_find_agent(usess, domain->type);
                if (!agt) {
                        agt = agent_create(domain->type);
@@ -2580,7 +2708,7 @@ int cmd_start_trace(struct ltt_session *session)
        session->rotated_after_last_stop = false;
 
        if (session->rotate_timer_period) {
-               ret = sessiond_rotate_timer_start(session,
+               ret = timer_session_rotation_schedule_timer_start(session,
                                session->rotate_timer_period);
                if (ret < 0) {
                        ERR("Failed to enable rotate timer");
@@ -2595,48 +2723,6 @@ error:
        return ret;
 }
 
-static
-int rename_active_chunk(struct ltt_session *session)
-{
-       int ret;
-
-       session->rotate_count++;
-
-       /*
-        * The currently active tracing path is now the folder we
-        * want to rename.
-        */
-       ret = lttng_strncpy(session->rotation_chunk.current_rotate_path,
-                       session->rotation_chunk.active_tracing_path,
-                       sizeof(session->rotation_chunk.current_rotate_path));
-       if (ret) {
-               ERR("Failed to copy active tracing path");
-               goto end;
-       }
-
-       ret = rename_complete_chunk(session, time(NULL));
-       if (ret < 0) {
-               ERR("Failed to rename current rotate path");
-               goto end;
-       }
-
-       /*
-        * We just renamed, the folder, we didn't do an actual rotation, so
-        * the active tracing path is now the renamed folder and we have to
-        * restore the rotate count.
-        */
-       ret = lttng_strncpy(session->rotation_chunk.active_tracing_path,
-                       session->rotation_chunk.current_rotate_path,
-                       sizeof(session->rotation_chunk.active_tracing_path));
-       if (ret) {
-               ERR("Failed to rename active session chunk tracing path");
-               goto end;
-       }
-end:
-       session->rotate_count--;
-       return ret;
-}
-
 /*
  * Command LTTNG_STOP_TRACE processed by the client thread.
  */
@@ -2646,7 +2732,7 @@ int cmd_stop_trace(struct ltt_session *session)
        struct ltt_kernel_channel *kchan;
        struct ltt_kernel_session *ksession;
        struct ltt_ust_session *usess;
-       bool error_occured = false;
+       bool error_occurred = false;
 
        assert(session);
 
@@ -2661,22 +2747,29 @@ int cmd_stop_trace(struct ltt_session *session)
                goto error;
        }
 
-       if (session->rotate_relay_pending_timer_enabled) {
-               sessiond_timer_rotate_pending_stop(session);
-       }
-
-       if (session->rotate_timer_enabled) {
-               sessiond_rotate_timer_stop(session);
+       if (session->rotation_schedule_timer_enabled) {
+               if (timer_session_rotation_schedule_timer_stop(
+                               session)) {
+                       ERR("Failed to stop the \"rotation schedule\" timer of session %s",
+                                       session->name);
+               }
        }
 
-       if (session->rotate_count > 0 && !session->rotate_pending) {
+       /*
+        * A rotation is still ongoing. The check timer will continue to wait
+        * for the rotation to complete. When the rotation finally completes,
+        * a check will be performed to rename the "active" chunk to the
+        * expected "timestamp_begin-timestamp_end" format.
+        */
+       if (session->current_archive_id > 0 &&
+                       session->rotation_state != LTTNG_ROTATION_STATE_ONGOING) {
                ret = rename_active_chunk(session);
                if (ret) {
                        /*
                         * This error should not prevent the user from stopping
                         * the session. However, it will be reported at the end.
                         */
-                       error_occured = true;
+                       error_occurred = true;
                }
        }
 
@@ -2729,7 +2822,7 @@ int cmd_stop_trace(struct ltt_session *session)
 
        /* Flag inactive after a successful stop. */
        session->active = 0;
-       ret = !error_occured ? LTTNG_OK : LTTNG_ERR_UNK;
+       ret = !error_occurred ? LTTNG_OK : LTTNG_ERR_UNK;
 
 error:
        return ret;
@@ -2817,39 +2910,31 @@ int cmd_create_session_uri(char *name, struct lttng_uri *uris,
                size_t nb_uri, lttng_sock_cred *creds, unsigned int live_timer)
 {
        int ret;
-       struct ltt_session *session;
+       struct ltt_session *session = NULL;
 
        assert(name);
        assert(creds);
 
-       /*
-        * Verify if the session already exist
-        *
-        * XXX: There is no need for the session lock list here since the caller
-        * (process_client_msg) is holding it. We might want to change that so a
-        * single command does not lock the entire session list.
-        */
+       /* Check if the session already exists. */
+       session_lock_list();
        session = session_find_by_name(name);
+       session_unlock_list();
        if (session != NULL) {
                ret = LTTNG_ERR_EXIST_SESS;
-               goto find_error;
+               goto end;
        }
 
        /* Create tracing session in the registry */
        ret = session_create(name, LTTNG_SOCK_GET_UID_CRED(creds),
                        LTTNG_SOCK_GET_GID_CRED(creds));
        if (ret != LTTNG_OK) {
-               goto session_error;
+               goto end;
        }
 
-       /*
-        * Get the newly created session pointer back
-        *
-        * XXX: There is no need for the session lock list here since the caller
-        * (process_client_msg) is holding it. We might want to change that so a
-        * single command does not lock the entire session list.
-        */
+       /* Get the newly created session pointer back. */
+       session_lock_list();
        session = session_find_by_name(name);
+       session_unlock_list();
        assert(session);
 
        session->live_timer = live_timer;
@@ -2857,13 +2942,13 @@ int cmd_create_session_uri(char *name, struct lttng_uri *uris,
        session->consumer = consumer_create_output(CONSUMER_DST_LOCAL);
        if (session->consumer == NULL) {
                ret = LTTNG_ERR_FATAL;
-               goto consumer_error;
+               goto end;
        }
 
        if (uris) {
                ret = cmd_set_consumer_uri(session, nb_uri, uris);
                if (ret != LTTNG_OK) {
-                       goto consumer_error;
+                       goto end;
                }
                session->output_traces = 1;
        } else {
@@ -2873,12 +2958,13 @@ int cmd_create_session_uri(char *name, struct lttng_uri *uris,
 
        session->consumer->enabled = 1;
 
-       return LTTNG_OK;
-
-consumer_error:
-       session_destroy(session);
-session_error:
-find_error:
+       ret = LTTNG_OK;
+end:
+       if (session) {
+               session_lock_list();
+               session_put(session);
+               session_unlock_list();
+       }
        return ret;
 }
 
@@ -2889,7 +2975,7 @@ int cmd_create_session_snapshot(char *name, struct lttng_uri *uris,
                size_t nb_uri, lttng_sock_cred *creds)
 {
        int ret;
-       struct ltt_session *session;
+       struct ltt_session *session = NULL;
        struct snapshot_output *new_output = NULL;
 
        assert(name);
@@ -2901,11 +2987,13 @@ int cmd_create_session_snapshot(char *name, struct lttng_uri *uris,
         */
        ret = cmd_create_session_uri(name, NULL, 0, creds, 0);
        if (ret != LTTNG_OK) {
-               goto error;
+               goto end;
        }
 
        /* Get the newly created session pointer back. This should NEVER fail. */
+       session_lock_list();
        session = session_find_by_name(name);
+       session_unlock_list();
        assert(session);
 
        /* Flag session for snapshot mode. */
@@ -2913,6 +3001,7 @@ int cmd_create_session_snapshot(char *name, struct lttng_uri *uris,
 
        /* Skip snapshot output creation if no URI is given. */
        if (nb_uri == 0) {
+               /* Not an error. */
                goto end;
        }
 
@@ -2937,14 +3026,18 @@ int cmd_create_session_snapshot(char *name, struct lttng_uri *uris,
        snapshot_add_output(&session->snapshot, new_output);
        rcu_read_unlock();
 
-end:
-       return LTTNG_OK;
+       ret = LTTNG_OK;
+       goto end;
 
 error_snapshot:
        snapshot_output_destroy(new_output);
 error_snapshot_alloc:
-       session_destroy(session);
-error:
+end:
+       if (session) {
+               session_lock_list();
+               session_put(session);
+               session_unlock_list();
+       }
        return ret;
 }
 
@@ -2953,27 +3046,29 @@ error:
  *
  * Called with session lock held.
  */
-int cmd_destroy_session(struct ltt_session *session, int wpipe,
+int cmd_destroy_session(struct ltt_session *session,
                struct notification_thread_handle *notification_thread_handle)
 {
        int ret;
-       struct ltt_ust_session *usess;
-       struct ltt_kernel_session *ksess;
 
        /* Safety net */
        assert(session);
 
-       usess = session->ust_session;
-       ksess = session->kernel_session;
-
        DBG("Begin destroy session %s (id %" PRIu64 ")", session->name, session->id);
 
-       if (session->rotate_relay_pending_timer_enabled) {
-               sessiond_timer_rotate_pending_stop(session);
+       if (session->rotation_pending_check_timer_enabled) {
+               if (timer_session_rotation_pending_check_stop(session)) {
+                       ERR("Failed to stop the \"rotation pending check\" timer of session %s",
+                                       session->name);
+               }
        }
 
-       if (session->rotate_timer_enabled) {
-               sessiond_rotate_timer_stop(session);
+       if (session->rotation_schedule_timer_enabled) {
+               if (timer_session_rotation_schedule_timer_stop(
+                               session)) {
+                       ERR("Failed to stop the \"rotation schedule\" timer of session %s",
+                                       session->name);
+               }
        }
 
        if (session->rotate_size) {
@@ -2990,34 +3085,67 @@ int cmd_destroy_session(struct ltt_session *session, int wpipe,
                rename_active_chunk(session);
        }
 
-       /* Clean kernel session teardown */
-       kernel_destroy_session(ksess);
-
-       /* UST session teardown */
-       if (usess) {
-               /* Close any relayd session */
-               consumer_output_send_destroy_relayd(usess->consumer);
-
-               /* Destroy every UST application related to this session. */
-               ret = ust_app_destroy_trace_all(usess);
-               if (ret) {
-                       ERR("Error in ust_app_destroy_trace_all");
-               }
-
-               /* Clean up the rest. */
-               trace_ust_destroy_session(usess);
+       if (session->shm_path[0]) {
+               /*
+                * When a session is created with an explicit shm_path,
+                * the consumer daemon will create its shared memory files
+                * at that location and will *not* unlink them. This is normal
+                * as the intention of that feature is to make it possible
+                * to retrieve the content of those files should a crash occur.
+                *
+                * To ensure the content of those files can be used, the
+                * sessiond daemon will replicate the content of the metadata
+                * cache in a metadata file.
+                *
+                * On clean-up, it is expected that the consumer daemon will
+                * unlink the shared memory files and that the session daemon
+                * will unlink the metadata file. Then, the session's directory
+                * in the shm path can be removed.
+                *
+                * Unfortunately, a flaw in the design of the sessiond's and
+                * consumerd's tear down of channels makes it impossible to
+                * determine when the sessiond _and_ the consumerd have both
+                * destroyed their representation of a channel. For one, the
+                * unlinking, close, and rmdir happen in deferred 'call_rcu'
+                * callbacks in both daemons.
+                *
+                * However, it is also impossible for the sessiond to know when
+                * the consumer daemon is done destroying its channel(s) since
+                * it occurs as a reaction to the closing of the channel's file
+                * descriptor. There is no resulting communication initiated
+                * from the consumerd to the sessiond to confirm that the
+                * operation is completed (and was successful).
+                *
+                * Until this is all fixed, the session daemon checks for the
+                * removal of the session's shm path which makes it possible
+                * to safely advertise a session as having been destroyed.
+                *
+                * Prior to this fix, it was not possible to reliably save
+                * a session making use of the --shm-path option, destroy it,
+                * and load it again. This is because the creation of the
+                * session would fail upon seeing the session's shm path
+                * already in existence.
+                *
+                * Note that none of the error paths in the check for the
+                * directory's existence return an error. This is normal
+                * as there isn't much that can be done. The session will
+                * be destroyed properly, except that we can't offer the
+                * guarantee that the same session can be re-created.
+                */
+               current_completion_handler = &destroy_completion_handler.handler;
+               ret = lttng_strncpy(destroy_completion_handler.shm_path,
+                               session->shm_path,
+                               sizeof(destroy_completion_handler.shm_path));
+               assert(!ret);
        }
 
        /*
-        * Must notify the kernel thread here to update it's poll set in order to
-        * remove the channel(s)' fd just destroyed.
+        * The session is destroyed. However, note that the command context
+        * still holds a reference to the session, thus delaying its destruction
+        * _at least_ up to the point when that reference is released.
         */
-       ret = notify_thread_pipe(wpipe);
-       if (ret < 0) {
-               PERROR("write kernel poll pipe");
-       }
-
-       ret = session_destroy(session);
+       session_destroy(session);
+       ret = LTTNG_OK;
 
        return ret;
 }
@@ -3322,10 +3450,15 @@ void cmd_list_lttng_sessions(struct lttng_session *sessions, uid_t uid,
         * the buffer.
         */
        cds_list_for_each_entry(session, &list->head, list) {
+               if (!session_get(session)) {
+                       continue;
+               }
                /*
                 * Only list the sessions the user can control.
                 */
-               if (!session_access_ok(session, uid, gid)) {
+               if (!session_access_ok(session, uid, gid) ||
+                               session->destroyed) {
+                       session_put(session);
                        continue;
                }
 
@@ -3343,6 +3476,7 @@ void cmd_list_lttng_sessions(struct lttng_session *sessions, uid_t uid,
                }
                if (ret < 0) {
                        PERROR("snprintf session path");
+                       session_put(session);
                        continue;
                }
 
@@ -3352,6 +3486,7 @@ void cmd_list_lttng_sessions(struct lttng_session *sessions, uid_t uid,
                sessions[i].snapshot_mode = session->snapshot_mode;
                sessions[i].live_timer_interval = session->live_timer;
                i++;
+               session_put(session);
        }
 }
 
@@ -3390,10 +3525,8 @@ int cmd_data_pending(struct ltt_session *session)
                }
        }
 
-       /*
-        * A rotation is still pending, we have to wait.
-        */
-       if (session->rotate_pending) {
+       /* A rotation is still pending, we have to wait. */
+       if (session->rotation_state == LTTNG_ROTATION_STATE_ONGOING) {
                DBG("Rotate still pending for session %s", session->name);
                ret = 1;
                goto error;
@@ -3671,10 +3804,12 @@ static
 int clear_metadata_file(int fd)
 {
        int ret;
+       off_t lseek_ret;
 
-       ret = lseek(fd, 0, SEEK_SET);
-       if (ret < 0) {
+       lseek_ret = lseek(fd, 0, SEEK_SET);
+       if (lseek_ret < 0) {
                PERROR("lseek");
+               ret = -1;
                goto end;
        }
 
@@ -3947,12 +4082,14 @@ end:
  * Send relayd sockets from snapshot output to consumer. Ignore request if the
  * snapshot output is *not* set with a remote destination.
  *
- * Return 0 on success or a LTTNG_ERR code.
+ * Return LTTNG_OK on success or a LTTNG_ERR code.
  */
-static int set_relayd_for_snapshot(struct consumer_output *consumer,
-               struct snapshot_output *snap_output, struct ltt_session *session)
+static enum lttng_error_code set_relayd_for_snapshot(
+               struct consumer_output *consumer,
+               struct snapshot_output *snap_output,
+               struct ltt_session *session)
 {
-       int ret = LTTNG_OK;
+       enum lttng_error_code status = LTTNG_OK;
        struct lttng_ht_iter iter;
        struct consumer_socket *socket;
 
@@ -3975,12 +4112,12 @@ static int set_relayd_for_snapshot(struct consumer_output *consumer,
        cds_lfht_for_each_entry(snap_output->consumer->socks->ht, &iter.iter,
                        socket, node.node) {
                pthread_mutex_lock(socket->lock);
-               ret = send_consumer_relayd_sockets(0, session->id,
+               status = send_consumer_relayd_sockets(0, session->id,
                                snap_output->consumer, socket,
                                session->name, session->hostname,
                                session->live_timer);
                pthread_mutex_unlock(socket->lock);
-               if (ret != LTTNG_OK) {
+               if (status != LTTNG_OK) {
                        rcu_read_unlock();
                        goto error;
                }
@@ -3988,7 +4125,7 @@ static int set_relayd_for_snapshot(struct consumer_output *consumer,
        rcu_read_unlock();
 
 error:
-       return ret;
+       return status;
 }
 
 /*
@@ -3996,38 +4133,37 @@ error:
  *
  * Return LTTNG_OK on success or a LTTNG_ERR code.
  */
-static int record_kernel_snapshot(struct ltt_kernel_session *ksess,
+static enum lttng_error_code record_kernel_snapshot(struct ltt_kernel_session *ksess,
                struct snapshot_output *output, struct ltt_session *session,
                int wait, uint64_t nb_packets_per_stream)
 {
        int ret;
+       enum lttng_error_code status;
 
        assert(ksess);
        assert(output);
        assert(session);
 
-
        /*
         * Copy kernel session sockets so we can communicate with the right
         * consumer for the snapshot record command.
         */
        ret = consumer_copy_sockets(output->consumer, ksess->consumer);
        if (ret < 0) {
-               ret = LTTNG_ERR_NOMEM;
+               status = LTTNG_ERR_NOMEM;
                goto error;
        }
 
-       ret = set_relayd_for_snapshot(ksess->consumer, output, session);
-       if (ret != LTTNG_OK) {
+       status = set_relayd_for_snapshot(ksess->consumer, output, session);
+       if (status != LTTNG_OK) {
                goto error_snapshot;
        }
 
-       ret = kernel_snapshot_record(ksess, output, wait, nb_packets_per_stream);
-       if (ret != LTTNG_OK) {
+       status = kernel_snapshot_record(ksess, output, wait, nb_packets_per_stream);
+       if (status != LTTNG_OK) {
                goto error_snapshot;
        }
 
-       ret = LTTNG_OK;
        goto end;
 
 error_snapshot:
@@ -4035,19 +4171,20 @@ error_snapshot:
        consumer_destroy_output_sockets(output->consumer);
 error:
 end:
-       return ret;
+       return status;
 }
 
 /*
  * Record a UST snapshot.
  *
- * Return 0 on success or a LTTNG_ERR error code.
+ * Returns LTTNG_OK on success or a LTTNG_ERR error code.
  */
-static int record_ust_snapshot(struct ltt_ust_session *usess,
+static enum lttng_error_code record_ust_snapshot(struct ltt_ust_session *usess,
                struct snapshot_output *output, struct ltt_session *session,
                int wait, uint64_t nb_packets_per_stream)
 {
        int ret;
+       enum lttng_error_code status;
 
        assert(usess);
        assert(output);
@@ -4059,35 +4196,25 @@ static int record_ust_snapshot(struct ltt_ust_session *usess,
         */
        ret = consumer_copy_sockets(output->consumer, usess->consumer);
        if (ret < 0) {
-               ret = LTTNG_ERR_NOMEM;
+               status = LTTNG_ERR_NOMEM;
                goto error;
        }
 
-       ret = set_relayd_for_snapshot(usess->consumer, output, session);
-       if (ret != LTTNG_OK) {
+       status = set_relayd_for_snapshot(usess->consumer, output, session);
+       if (status != LTTNG_OK) {
                goto error_snapshot;
        }
 
-       ret = ust_app_snapshot_record(usess, output, wait, nb_packets_per_stream);
-       if (ret < 0) {
-               switch (-ret) {
-               case EINVAL:
-                       ret = LTTNG_ERR_INVALID;
-                       break;
-               default:
-                       ret = LTTNG_ERR_SNAPSHOT_FAIL;
-                       break;
-               }
+       status = ust_app_snapshot_record(usess, output, wait, nb_packets_per_stream);
+       if (status != LTTNG_OK) {
                goto error_snapshot;
        }
 
-       ret = LTTNG_OK;
-
 error_snapshot:
        /* Clean up copied sockets so this output can use some other later on. */
        consumer_destroy_output_sockets(output->consumer);
 error:
-       return ret;
+       return status;
 }
 
 static
@@ -4187,7 +4314,8 @@ int64_t get_session_nb_packets_per_stream(struct ltt_session *session, uint64_t
 int cmd_snapshot_record(struct ltt_session *session,
                struct lttng_snapshot_output *output, int wait)
 {
-       int ret = LTTNG_OK;
+       enum lttng_error_code cmd_ret = LTTNG_OK;
+       int ret;
        unsigned int use_tmp_output = 0;
        struct snapshot_output tmp_output;
        unsigned int snapshot_success = 0;
@@ -4202,7 +4330,7 @@ int cmd_snapshot_record(struct ltt_session *session,
        ret = utils_get_current_time_str("%Y%m%d-%H%M%S", datetime,
                        sizeof(datetime));
        if (!ret) {
-               ret = LTTNG_ERR_INVALID;
+               cmd_ret = LTTNG_ERR_INVALID;
                goto error;
        }
 
@@ -4211,13 +4339,13 @@ int cmd_snapshot_record(struct ltt_session *session,
         * set in no output mode.
         */
        if (session->output_traces) {
-               ret = LTTNG_ERR_NOT_SNAPSHOT_SESSION;
+               cmd_ret = LTTNG_ERR_NOT_SNAPSHOT_SESSION;
                goto error;
        }
 
        /* The session needs to be started at least once. */
        if (!session->has_been_started) {
-               ret = LTTNG_ERR_START_SESSION_ONCE;
+               cmd_ret = LTTNG_ERR_START_SESSION_ONCE;
                goto error;
        }
 
@@ -4228,9 +4356,9 @@ int cmd_snapshot_record(struct ltt_session *session,
                                &tmp_output, NULL);
                if (ret < 0) {
                        if (ret == -ENOMEM) {
-                               ret = LTTNG_ERR_NOMEM;
+                               cmd_ret = LTTNG_ERR_NOMEM;
                        } else {
-                               ret = LTTNG_ERR_INVALID;
+                               cmd_ret = LTTNG_ERR_INVALID;
                        }
                        goto error;
                }
@@ -4248,24 +4376,24 @@ int cmd_snapshot_record(struct ltt_session *session,
                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;
+                       cmd_ret = LTTNG_ERR_MAX_SIZE_INVALID;
                        goto error;
                }
 
                if (session->kernel_session) {
-                       ret = record_kernel_snapshot(session->kernel_session,
+                       cmd_ret = record_kernel_snapshot(session->kernel_session,
                                        &tmp_output, session,
                                        wait, nb_packets_per_stream);
-                       if (ret != LTTNG_OK) {
+                       if (cmd_ret != LTTNG_OK) {
                                goto error;
                        }
                }
 
                if (session->ust_session) {
-                       ret = record_ust_snapshot(session->ust_session,
+                       cmd_ret = record_ust_snapshot(session->ust_session,
                                        &tmp_output, session,
                                        wait, nb_packets_per_stream);
-                       if (ret != LTTNG_OK) {
+                       if (cmd_ret != LTTNG_OK) {
                                goto error;
                        }
                }
@@ -4294,7 +4422,7 @@ int cmd_snapshot_record(struct ltt_session *session,
                        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;
+                               cmd_ret = LTTNG_ERR_MAX_SIZE_INVALID;
                                rcu_read_unlock();
                                goto error;
                        }
@@ -4303,7 +4431,7 @@ int cmd_snapshot_record(struct ltt_session *session,
                        if (*output->name != '\0') {
                                if (lttng_strncpy(tmp_output.name, output->name,
                                                sizeof(tmp_output.name))) {
-                                       ret = LTTNG_ERR_INVALID;
+                                       cmd_ret = LTTNG_ERR_INVALID;
                                        rcu_read_unlock();
                                        goto error;
                                }
@@ -4313,20 +4441,20 @@ int cmd_snapshot_record(struct ltt_session *session,
                        memcpy(tmp_output.datetime, datetime, sizeof(datetime));
 
                        if (session->kernel_session) {
-                               ret = record_kernel_snapshot(session->kernel_session,
+                               cmd_ret = record_kernel_snapshot(session->kernel_session,
                                                &tmp_output, session,
                                                wait, nb_packets_per_stream);
-                               if (ret != LTTNG_OK) {
+                               if (cmd_ret != LTTNG_OK) {
                                        rcu_read_unlock();
                                        goto error;
                                }
                        }
 
                        if (session->ust_session) {
-                               ret = record_ust_snapshot(session->ust_session,
+                               cmd_ret = record_ust_snapshot(session->ust_session,
                                                &tmp_output, session,
                                                wait, nb_packets_per_stream);
-                               if (ret != LTTNG_OK) {
+                               if (cmd_ret != LTTNG_OK) {
                                        rcu_read_unlock();
                                        goto error;
                                }
@@ -4339,11 +4467,11 @@ int cmd_snapshot_record(struct ltt_session *session,
        if (snapshot_success) {
                session->snapshot.nb_snapshot++;
        } else {
-               ret = LTTNG_ERR_SNAPSHOT_FAIL;
+               cmd_ret = LTTNG_ERR_SNAPSHOT_FAIL;
        }
 
 error:
-       return ret;
+       return cmd_ret;
 }
 
 /*
@@ -4375,28 +4503,33 @@ int cmd_set_session_shm_path(struct ltt_session *session,
  * Ask the consumer to rotate the session output directory.
  * The session lock must be held.
  *
- * Return LTTNG_OK on success or else a LTTNG_ERR code.
+ * Returns LTTNG_OK on success or else a negative LTTng error code.
  */
 int cmd_rotate_session(struct ltt_session *session,
                struct lttng_rotate_session_return *rotate_return)
 {
        int ret;
+       enum lttng_error_code cmd_ret = LTTNG_OK;
        size_t strf_ret;
        struct tm *timeinfo;
        char datetime[21];
        time_t now;
-       bool ust_active = false;
+       /*
+        * Used to roll-back timestamps in case of failure to launch the
+        * rotation.
+        */
+       time_t original_last_chunk_start_ts, original_current_chunk_start_ts;
 
        assert(session);
 
        if (!session->has_been_started) {
-               ret = -LTTNG_ERR_START_SESSION_ONCE;
+               cmd_ret = LTTNG_ERR_START_SESSION_ONCE;
                goto end;
        }
 
        if (session->live_timer || session->snapshot_mode ||
                        !session->output_traces) {
-               ret = -LTTNG_ERR_ROTATION_NOT_AVAILABLE;
+               cmd_ret = LTTNG_ERR_ROTATION_NOT_AVAILABLE;
                goto end;
        }
 
@@ -4406,13 +4539,14 @@ int cmd_rotate_session(struct ltt_session *session,
        if (session->consumer->type == CONSUMER_DST_NET &&
                        (session->consumer->relay_major_version == 2 &&
                        session->consumer->relay_minor_version < 11)) {
-               ret = -LTTNG_ERR_ROTATION_NOT_AVAILABLE_RELAY;
+               cmd_ret = LTTNG_ERR_ROTATION_NOT_AVAILABLE_RELAY;
                goto end;
        }
 
-       if (session->rotate_pending || session->rotate_pending_relay) {
-               ret = -LTTNG_ERR_ROTATION_PENDING;
-               DBG("Rotate already in progress");
+       if (session->rotation_state == LTTNG_ROTATION_STATE_ONGOING) {
+               DBG("Refusing to launch a rotation; a rotation is already in progress for session %s",
+                               session->name);
+               cmd_ret = LTTNG_ERR_ROTATION_PENDING;
                goto end;
        }
 
@@ -4423,29 +4557,25 @@ int cmd_rotate_session(struct ltt_session *session,
        if (session->rotated_after_last_stop) {
                DBG("Session \"%s\" was already rotated after stop, refusing rotation",
                                session->name);
-               ret = -LTTNG_ERR_ROTATION_MULTIPLE_AFTER_STOP;
+               cmd_ret = LTTNG_ERR_ROTATION_MULTIPLE_AFTER_STOP;
                goto end;
        }
 
        /* Special case for the first rotation. */
-       if (session->rotate_count == 0) {
+       if (session->current_archive_id == 0) {
                const char *base_path = NULL;
 
+               assert(session->kernel_session || session->ust_session);
                /* Either one of the two sessions is enough to get the root path. */
-               if (session->kernel_session) {
-                       base_path = session_get_base_path(session);
-               } else if (session->ust_session) {
-                       base_path = session_get_base_path(session);
-               } else {
-                       assert(0);
-               }
+               base_path = session_get_base_path(session);
                assert(base_path);
+
                ret = lttng_strncpy(session->rotation_chunk.current_rotate_path,
                                base_path,
                                sizeof(session->rotation_chunk.current_rotate_path));
                if (ret) {
                        ERR("Failed to copy session base path to current rotation chunk path");
-                       ret = -LTTNG_ERR_UNK;
+                       cmd_ret = LTTNG_ERR_UNK;
                        goto end;
                }
        } else {
@@ -4458,40 +4588,54 @@ int cmd_rotate_session(struct ltt_session *session,
                                sizeof(session->rotation_chunk.current_rotate_path));
                if (ret) {
                        ERR("Failed to copy the active tracing path to the current rotate path");
-                       ret = -LTTNG_ERR_UNK;
+                       cmd_ret = LTTNG_ERR_UNK;
                        goto end;
                }
        }
        DBG("Current rotate path %s", session->rotation_chunk.current_rotate_path);
 
-       session->rotate_count++;
-       session->rotate_pending = true;
-       session->rotation_state = LTTNG_ROTATION_STATE_ONGOING;
-
        /*
-        * Create the path name for the next chunk.
+        * Channels created after this point will belong to the next
+        * archive id.
         */
+       session->current_archive_id++;
+
        now = time(NULL);
        if (now == (time_t) -1) {
-               ret = -LTTNG_ERR_ROTATION_NOT_AVAILABLE;
+               cmd_ret = LTTNG_ERR_UNK;
                goto end;
        }
+
+       /* Sample chunk bounds for roll-back in case of error. */
+       original_last_chunk_start_ts = session->last_chunk_start_ts;
+       original_current_chunk_start_ts = session->current_chunk_start_ts;
+
        session->last_chunk_start_ts = session->current_chunk_start_ts;
        session->current_chunk_start_ts = now;
 
        timeinfo = localtime(&now);
        if (!timeinfo) {
                PERROR("Failed to sample local time in rotate session command");
-               ret = -LTTNG_ERR_UNK;
+               cmd_ret = LTTNG_ERR_UNK;
                goto end;
        }
        strf_ret = strftime(datetime, sizeof(datetime), "%Y%m%dT%H%M%S%z",
                        timeinfo);
        if (!strf_ret) {
                ERR("Failed to format local time timestamp in rotate session command");
-               ret = -LTTNG_ERR_UNK;
+               cmd_ret = LTTNG_ERR_UNK;
                goto end;
        }
+
+       /*
+        * A rotation has a local step even if the destination is a relay
+        * daemon; the buffers must be consumed by the consumer daemon.
+        */
+       session->rotation_pending_local = true;
+       session->rotation_pending_relay =
+               session_get_consumer_destination_type(session) == CONSUMER_DST_NET;
+       session->rotation_state = LTTNG_ROTATION_STATE_ONGOING;
+
        if (session->kernel_session) {
                /*
                 * The active path for the next rotation/destroy.
@@ -4501,11 +4645,11 @@ int cmd_rotate_session(struct ltt_session *session,
                                sizeof(session->rotation_chunk.active_tracing_path),
                                "%s/%s-%" PRIu64,
                                session_get_base_path(session),
-                               datetime, session->rotate_count + 1);
+                               datetime, session->current_archive_id + 1);
                if (ret < 0 || ret == sizeof(session->rotation_chunk.active_tracing_path)) {
                        ERR("Failed to format active kernel tracing path in rotate session command");
-                       ret = -LTTNG_ERR_UNK;
-                       goto end;
+                       cmd_ret = LTTNG_ERR_UNK;
+                       goto error;
                }
                /*
                 * The sub-directory for the consumer
@@ -4514,11 +4658,11 @@ int cmd_rotate_session(struct ltt_session *session,
                ret = snprintf(session->kernel_session->consumer->chunk_path,
                                sizeof(session->kernel_session->consumer->chunk_path),
                                "/%s-%" PRIu64, datetime,
-                               session->rotate_count + 1);
+                               session->current_archive_id + 1);
                if (ret < 0 || ret == sizeof(session->kernel_session->consumer->chunk_path)) {
                        ERR("Failed to format the kernel consumer's sub-directory in rotate session command");
-                       ret = -LTTNG_ERR_UNK;
-                       goto end;
+                       cmd_ret = LTTNG_ERR_UNK;
+                       goto error;
                }
                /*
                 * Create the new chunk folder, before the rotation begins so we don't
@@ -4530,32 +4674,31 @@ int cmd_rotate_session(struct ltt_session *session,
                if (ret) {
                        ERR("Failed to create kernel session tracing path at %s",
                                        session->kernel_session->consumer->chunk_path);
-                       ret = -LTTNG_ERR_CREATE_DIR_FAIL;
-                       goto end;
+                       cmd_ret = LTTNG_ERR_CREATE_DIR_FAIL;
+                       goto error;
                }
-               ret = kernel_rotate_session(session);
-               if (ret != LTTNG_OK) {
-                       ret = -ret;
-                       goto end;
+               cmd_ret = kernel_rotate_session(session);
+               if (cmd_ret != LTTNG_OK) {
+                       goto error;
                }
        }
        if (session->ust_session) {
                ret = snprintf(session->rotation_chunk.active_tracing_path,
                                PATH_MAX, "%s/%s-%" PRIu64,
                                session_get_base_path(session),
-                               datetime, session->rotate_count + 1);
+                               datetime, session->current_archive_id + 1);
                if (ret < 0) {
                        ERR("Failed to format active UST tracing path in rotate session command");
-                       ret = -LTTNG_ERR_UNK;
-                       goto end;
+                       cmd_ret = LTTNG_ERR_UNK;
+                       goto error;
                }
                ret = snprintf(session->ust_session->consumer->chunk_path,
                                PATH_MAX, "/%s-%" PRIu64, datetime,
-                               session->rotate_count + 1);
+                               session->current_archive_id + 1);
                if (ret < 0) {
                        ERR("Failed to format the UST consumer's sub-directory in rotate session command");
-                       ret = -LTTNG_ERR_UNK;
-                       goto end;
+                       cmd_ret = LTTNG_ERR_UNK;
+                       goto error;
                }
                /*
                 * Create the new chunk folder, before the rotation begins so we don't
@@ -4565,44 +4708,54 @@ int cmd_rotate_session(struct ltt_session *session,
                                session->ust_session->uid,
                                session->ust_session->gid);
                if (ret) {
-                       ret = -LTTNG_ERR_CREATE_DIR_FAIL;
-                       goto end;
-               }
-               ret = ust_app_rotate_session(session, &ust_active);
-               if (ret != LTTNG_OK) {
-                       goto end;
+                       cmd_ret = LTTNG_ERR_CREATE_DIR_FAIL;
+                       goto error;
                }
-               /*
-                * Handle the case where we did not start a rotation on any channel.
-                * The consumer will never wake up the rotation thread to perform the
-                * rename, so we have to do it here while we hold the session and
-                * session_list locks.
-                */
-               if (!session->kernel_session && !ust_active) {
-                       ret = rename_complete_chunk(session, now);
-                       if (ret < 0) {
-                               ERR("Failed to rename completed rotation chunk");
-                               goto end;
-                       }
-                       session->rotate_pending = false;
-                       session->rotation_state = LTTNG_ROTATION_STATE_COMPLETED;
+               cmd_ret = ust_app_rotate_session(session);
+               if (cmd_ret != LTTNG_OK) {
+                       goto error;
                }
        }
 
+       ret = timer_session_rotation_pending_check_start(session,
+                       DEFAULT_ROTATE_PENDING_TIMER);
+       if (ret) {
+               cmd_ret = LTTNG_ERR_UNK;
+               goto error;
+       }
+
        if (!session->active) {
                session->rotated_after_last_stop = true;
        }
 
        if (rotate_return) {
-               rotate_return->rotation_id = session->rotate_count;
+               rotate_return->rotation_id = session->current_archive_id;
        }
 
-       DBG("Cmd rotate session %s, rotate_id %" PRIu64 " sent", session->name,
-                       session->rotate_count);
-       ret = LTTNG_OK;
+       ret = notification_thread_command_session_rotation_ongoing(
+                       notification_thread_handle,
+                       session->name, session->uid, session->gid,
+                       session->current_archive_id - 1);
+       if (ret != LTTNG_OK) {
+               ERR("Failed to notify notification thread that a session rotation is ongoing for session %s",
+                               session->name);
+               cmd_ret = ret;
+       }
 
+       DBG("Cmd rotate session %s, archive_id %" PRIu64 " sent",
+                       session->name, session->current_archive_id - 1);
 end:
+       ret = (cmd_ret == LTTNG_OK) ? cmd_ret : -((int) cmd_ret);
        return ret;
+error:
+       session->last_chunk_start_ts = original_last_chunk_start_ts;
+       session->current_archive_id = original_current_chunk_start_ts;
+       if (session_reset_rotation_state(session,
+                       LTTNG_ROTATION_STATE_NO_ROTATION)) {
+               ERR("Failed to reset rotation state of session \"%s\"",
+                               session->name);
+       }
+       goto end;
 }
 
 /*
@@ -4621,9 +4774,9 @@ int cmd_rotate_get_info(struct ltt_session *session,
        assert(session);
 
        DBG("Cmd rotate_get_info session %s, rotation id %" PRIu64, session->name,
-                       session->rotate_count);
+                       session->current_archive_id);
 
-       if (session->rotate_count != rotation_id) {
+       if (session->current_archive_id != rotation_id) {
                info_return->status = (int32_t) LTTNG_ROTATION_STATE_EXPIRED;
                ret = LTTNG_OK;
                goto end;
@@ -4635,16 +4788,59 @@ int cmd_rotate_get_info(struct ltt_session *session,
                                rotation_id, session->name);
                break;
        case LTTNG_ROTATION_STATE_COMPLETED:
-               ret = lttng_strncpy(info_return->path,
+       {
+               char *current_tracing_path_reply;
+               size_t current_tracing_path_reply_len;
+
+               switch (session_get_consumer_destination_type(session)) {
+               case CONSUMER_DST_LOCAL:
+                       current_tracing_path_reply =
+                                       info_return->location.local.absolute_path;
+                       current_tracing_path_reply_len =
+                                       sizeof(info_return->location.local.absolute_path);
+                       info_return->location_type =
+                                       (int8_t) LTTNG_TRACE_ARCHIVE_LOCATION_TYPE_LOCAL;
+                       break;
+               case CONSUMER_DST_NET:
+                       current_tracing_path_reply =
+                                       info_return->location.relay.relative_path;
+                       current_tracing_path_reply_len =
+                                       sizeof(info_return->location.relay.relative_path);
+                       /* Currently the only supported relay protocol. */
+                       info_return->location.relay.protocol =
+                                       (int8_t) LTTNG_TRACE_ARCHIVE_LOCATION_RELAY_PROTOCOL_TYPE_TCP;
+
+                       ret = lttng_strncpy(info_return->location.relay.host,
+                                       session_get_net_consumer_hostname(session),
+                                       sizeof(info_return->location.relay.host));
+                       if (ret) {
+                               ERR("Failed to host name to rotate_get_info reply");
+                               info_return->status = LTTNG_ROTATION_STATUS_ERROR;
+                               ret = -LTTNG_ERR_UNK;
+                               goto end;
+                       }
+
+                       session_get_net_consumer_ports(session,
+                                       &info_return->location.relay.ports.control,
+                                       &info_return->location.relay.ports.data);
+                       info_return->location_type =
+                                       (int8_t) LTTNG_TRACE_ARCHIVE_LOCATION_TYPE_RELAY;
+                       break;
+               default:
+                       abort();
+               }
+               ret = lttng_strncpy(current_tracing_path_reply,
                                session->rotation_chunk.current_rotate_path,
-                               sizeof(info_return->path));
+                               current_tracing_path_reply_len);
                if (ret) {
-                       ERR("Failed to copy active tracing path to rotate_get_info reply");
+                       ERR("Failed to copy current tracing path to rotate_get_info reply");
                        info_return->status = LTTNG_ROTATION_STATUS_ERROR;
                        ret = -LTTNG_ERR_UNK;
                        goto end;
                }
+
                break;
+       }
        case LTTNG_ROTATION_STATE_ERROR:
                DBG("Reporting that an error occurred during rotation %" PRIu64 " of session %s",
                                rotation_id, session->name);
@@ -4663,15 +4859,19 @@ end:
  * Command LTTNG_ROTATION_SET_SCHEDULE from the lttng-ctl library.
  *
  * Configure the automatic rotation parameters.
- * Set to -1ULL to disable them.
+ * 'activate' to true means activate the rotation schedule type with 'new_value'.
+ * 'activate' to false means deactivate the rotation schedule and validate that
+ * 'new_value' has the same value as the currently active value.
  *
- * Return 0 on success or else an LTTNG_ERR code.
+ * Return 0 on success or else a positive LTTNG_ERR code.
  */
 int cmd_rotation_set_schedule(struct ltt_session *session,
-               uint64_t timer_us, uint64_t size,
+               bool activate, enum lttng_rotation_schedule_type schedule_type,
+               uint64_t new_value,
                struct notification_thread_handle *notification_thread_handle)
 {
        int ret;
+       uint64_t *parameter_value;
 
        assert(session);
 
@@ -4679,71 +4879,119 @@ int cmd_rotation_set_schedule(struct ltt_session *session,
 
        if (session->live_timer || session->snapshot_mode ||
                        !session->output_traces) {
+               DBG("Failing ROTATION_SET_SCHEDULE command as the rotation feature is not available for this session");
                ret = LTTNG_ERR_ROTATION_NOT_AVAILABLE;
                goto end;
        }
 
-       /* Trying to override an already active timer. */
-       if (timer_us && timer_us != -1ULL && session->rotate_timer_period) {
-               ret = LTTNG_ERR_ROTATION_TIMER_SET;
+       switch (schedule_type) {
+       case LTTNG_ROTATION_SCHEDULE_TYPE_SIZE_THRESHOLD:
+               parameter_value = &session->rotate_size;
+               break;
+       case LTTNG_ROTATION_SCHEDULE_TYPE_PERIODIC:
+               parameter_value = &session->rotate_timer_period;
+               if (new_value >= UINT_MAX) {
+                       DBG("Failing ROTATION_SET_SCHEDULE command as the value requested for a periodic rotation schedule is invalid: %" PRIu64 " > %u (UINT_MAX)",
+                                       new_value, UINT_MAX);
+                       ret = LTTNG_ERR_INVALID;
+                       goto end;
+               }
+               break;
+       default:
+               WARN("Failing ROTATION_SET_SCHEDULE command on unknown schedule type");
+               ret = LTTNG_ERR_INVALID;
                goto end;
-       /* Trying to disable an inactive timer. */
-       } else if (timer_us == -1ULL && !session->rotate_timer_period) {
-               ret = LTTNG_ERR_ROTATION_NO_TIMER_SET;
+       }
+
+       /* Improper use of the API. */
+       if (new_value == -1ULL) {
+               WARN("Failing ROTATION_SET_SCHEDULE command as the value requested is -1");
+               ret = LTTNG_ERR_INVALID;
                goto end;
        }
 
-       if (size && size != -1ULL && session->rotate_size) {
-               ret = LTTNG_ERR_ROTATION_SIZE_SET;
+       /*
+        * As indicated in struct ltt_session's comments, a value of == 0 means
+        * this schedule rotation type is not in use.
+        *
+        * Reject the command if we were asked to activate a schedule that was
+        * already active.
+        */
+       if (activate && *parameter_value != 0) {
+               DBG("Failing ROTATION_SET_SCHEDULE (activate) command as the schedule is already active");
+               ret = LTTNG_ERR_ROTATION_SCHEDULE_SET;
                goto end;
-       } else if (size == -1ULL && !session->rotate_size) {
-               ret = LTTNG_ERR_ROTATION_NO_SIZE_SET;
+       }
+
+       /*
+        * Reject the command if we were asked to deactivate a schedule that was
+        * not active.
+        */
+       if (!activate && *parameter_value == 0) {
+               DBG("Failing ROTATION_SET_SCHEDULE (deactivate) command as the schedule is already inactive");
+               ret = LTTNG_ERR_ROTATION_SCHEDULE_NOT_SET;
                goto end;
        }
 
-       if (timer_us && !session->rotate_timer_period) {
-               if (timer_us > UINT_MAX) {
-                       ret = LTTNG_ERR_INVALID;
-                       goto end;
-               }
+       /*
+        * Reject the command if we were asked to deactivate a schedule that
+        * doesn't exist.
+        */
+       if (!activate && *parameter_value != new_value) {
+               DBG("Failing ROTATION_SET_SCHEDULE (deactivate) command as an inexistant schedule was provided");
+               ret = LTTNG_ERR_ROTATION_SCHEDULE_NOT_SET;
+               goto end;
+       }
 
-               session->rotate_timer_period = timer_us;
-               /*
-                * Only start the timer if the session is active, otherwise
-                * it will be started when the session starts.
-                */
-               if (session->active) {
-                       ret = sessiond_rotate_timer_start(session, timer_us);
+       *parameter_value = activate ? new_value : 0;
+
+       switch (schedule_type) {
+       case LTTNG_ROTATION_SCHEDULE_TYPE_PERIODIC:
+               if (activate && session->active) {
+                       /*
+                        * Only start the timer if the session is active,
+                        * otherwise it will be started when the session starts.
+                        */
+                       ret = timer_session_rotation_schedule_timer_start(
+                                       session, new_value);
+                       if (ret) {
+                               ERR("Failed to enable session rotation timer in ROTATION_SET_SCHEDULE command");
+                               ret = LTTNG_ERR_UNK;
+                               goto end;
+                       }
+               } else {
+                       ret = timer_session_rotation_schedule_timer_stop(
+                                       session);
                        if (ret) {
-                               ERR("Failed to enable rotate timer");
+                               ERR("Failed to disable session rotation timer in ROTATION_SET_SCHEDULE command");
                                ret = LTTNG_ERR_UNK;
                                goto end;
                        }
                }
-       } else if (timer_us == -1ULL && session->rotate_timer_period > 0) {
-               sessiond_rotate_timer_stop(session);
-               session->rotate_timer_period = 0;
-       }
-
-       if (size > 0) {
-               if (size == -1ULL) {
-                       ret = unsubscribe_session_consumed_size_rotation(session,
-                                       notification_thread_handle);
+               break;
+       case LTTNG_ROTATION_SCHEDULE_TYPE_SIZE_THRESHOLD:
+               if (activate) {
+                       ret = subscribe_session_consumed_size_rotation(session,
+                                       new_value, notification_thread_handle);
                        if (ret) {
+                               ERR("Failed to enable consumed-size notification in ROTATION_SET_SCHEDULE command");
                                ret = LTTNG_ERR_UNK;
                                goto end;
                        }
-                       session->rotate_size = 0;
                } else {
-                       ret = subscribe_session_consumed_size_rotation(session,
-                                       size, notification_thread_handle);
+                       ret = unsubscribe_session_consumed_size_rotation(session,
+                                       notification_thread_handle);
                        if (ret) {
-                               PERROR("Subscribe to session usage");
+                               ERR("Failed to disable consumed-size notification in ROTATION_SET_SCHEDULE command");
                                ret = LTTNG_ERR_UNK;
                                goto end;
                        }
-                       session->rotate_size = size;
+
                }
+               break;
+       default:
+               /* Would have been caught before. */
+               abort();
        }
 
        ret = LTTNG_OK;
@@ -4754,56 +5002,47 @@ end:
        return ret;
 }
 
-/*
- * Command ROTATE_GET_CURRENT_PATH from the lttng-ctl library.
- *
- * Configure the automatic rotation parameters.
- * Set to -1ULL to disable them.
- *
- * Return LTTNG_OK on success or else a LTTNG_ERR code.
- */
-int cmd_session_get_current_output(struct ltt_session *session,
-               struct lttng_session_get_current_output_return *output_return)
+/* Wait for a given path to be removed before continuing. */
+static enum lttng_error_code wait_on_path(void *path_data)
 {
-       int ret;
-       const char *path;
+       const char *shm_path = path_data;
 
-       if (!session->snapshot_mode) {
-               if (session->rotate_count == 0) {
-                       if (session->kernel_session) {
-                               path = session_get_base_path(session);
-                       } else if (session->ust_session) {
-                               path = session_get_base_path(session);
+       DBG("Waiting for the shm path at %s to be removed before completing session destruction",
+                       shm_path);
+       while (true) {
+               int ret;
+               struct stat st;
+
+               ret = stat(shm_path, &st);
+               if (ret) {
+                       if (errno != ENOENT) {
+                               PERROR("stat() returned an error while checking for the existence of the shm path");
                        } else {
-                               abort();
+                               DBG("shm path no longer exists, completing the destruction of session");
                        }
-                       assert(path);
+                       break;
                } else {
-                       path = session->rotation_chunk.active_tracing_path;
+                       if (!S_ISDIR(st.st_mode)) {
+                               ERR("The type of shm path %s returned by stat() is not a directory; aborting the wait for shm path removal",
+                                               shm_path);
+                               break;
+                       }
                }
-       } else {
-               /*
-                * A snapshot session does not have a "current" trace archive
-                * location.
-                */
-               path = "";
+               usleep(SESSION_DESTROY_SHM_PATH_CHECK_DELAY_US);
        }
+       return LTTNG_OK;
+}
 
-       DBG("Cmd get current output for session %s, returning %s",
-                       session->name, path);
-
-       ret = lttng_strncpy(output_return->path,
-                       path,
-                       sizeof(output_return->path));
-       if (ret) {
-               ERR("Failed to copy trace output path to session get current output command reply");
-               ret = -LTTNG_ERR_UNK;
-               goto end;
-       }
+/*
+ * Returns a pointer to a handler to run on completion of a command.
+ * Returns NULL if no handler has to be run for the last command executed.
+ */
+const struct cmd_completion_handler *cmd_pop_completion_handler(void)
+{
+       struct cmd_completion_handler *handler = current_completion_handler;
 
-       ret = LTTNG_OK;
-end:
-       return ret;
+       current_completion_handler = NULL;
+       return handler;
 }
 
 /*
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