Fix: cmd_rotate_session() returns unexpected error codes
[lttng-tools.git] / src / bin / lttng-sessiond / cmd.c
index 27acbada09627970ee2c6a46ebe301bacf4e2ae9..50bacf0c236dc3ea4917a6f4100a80aa39b98623 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>
@@ -36,6 +37,9 @@
 #include <lttng/action/action.h>
 #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 "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
@@ -353,9 +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) {
@@ -365,14 +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;
@@ -382,9 +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));
@@ -403,6 +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;
 }
 
 /*
@@ -416,7 +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;
@@ -444,8 +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();
 
@@ -470,17 +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;
 }
 
 /*
@@ -529,8 +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. */
@@ -590,8 +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;
@@ -633,14 +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;
        }
 
@@ -669,6 +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,
@@ -681,14 +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:
@@ -913,8 +1026,8 @@ error:
  *
  * The consumer socket lock must be held by the caller.
  */
-static int send_consumer_relayd_socket(enum lttng_domain_type domain,
-               unsigned int session_id, struct lttng_uri *relayd_uri,
+static int 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)
@@ -999,7 +1112,7 @@ static int send_consumer_relayd_sockets(enum lttng_domain_type domain,
 
        /* Sending control relayd socket. */
        if (!sock->control_sock_sent) {
-               ret = send_consumer_relayd_socket(domain, session_id,
+               ret = send_consumer_relayd_socket(session_id,
                                &consumer->dst.net.control, consumer, sock,
                                session_name, hostname, session_live_timer);
                if (ret != LTTNG_OK) {
@@ -1009,7 +1122,7 @@ static int send_consumer_relayd_sockets(enum lttng_domain_type domain,
 
        /* Sending data relayd socket. */
        if (!sock->data_sock_sent) {
-               ret = send_consumer_relayd_socket(domain, session_id,
+               ret = send_consumer_relayd_socket(session_id,
                                &consumer->dst.net.data, consumer, sock,
                                session_name, hostname, session_live_timer);
                if (ret != LTTNG_OK) {
@@ -1148,7 +1261,7 @@ 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;
 
@@ -1380,9 +1493,15 @@ 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;
@@ -1959,6 +2078,7 @@ 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:
@@ -2056,8 +2176,7 @@ 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;
                        }
@@ -2090,6 +2209,12 @@ 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);
@@ -2519,8 +2644,31 @@ int cmd_start_trace(struct ltt_session *session)
                goto error;
        }
 
+       /*
+        * Record the timestamp of the first time the session is started for
+        * an eventual session rotation call.
+        */
+       if (!session->has_been_started) {
+               session->current_chunk_start_ts = time(NULL);
+               if (session->current_chunk_start_ts == (time_t) -1) {
+                       PERROR("Failed to retrieve the \"%s\" session's start time",
+                                       session->name);
+                       ret = LTTNG_ERR_FATAL;
+                       goto error;
+               }
+               if (!session->snapshot_mode && session->output_traces) {
+                       ret = session_mkdir(session);
+                       if (ret) {
+                               ERR("Failed to create the session directories");
+                               ret = LTTNG_ERR_CREATE_DIR_FAIL;
+                               goto error;
+                       }
+               }
+       }
+
        /* Kernel tracing */
        if (ksession != NULL) {
+               DBG("Start kernel tracing session %s", session->name);
                ret = start_kernel_session(ksession, kernel_tracer_fd);
                if (ret != LTTNG_OK) {
                        goto error;
@@ -2546,6 +2694,22 @@ int cmd_start_trace(struct ltt_session *session)
        session->has_been_started = 1;
        session->active = 1;
 
+       /*
+        * Clear the flag that indicates that a rotation was done while the
+        * session was stopped.
+        */
+       session->rotated_after_last_stop = false;
+
+       if (session->rotate_timer_period) {
+               ret = timer_session_rotation_schedule_timer_start(session,
+                               session->rotate_timer_period);
+               if (ret < 0) {
+                       ERR("Failed to enable rotate timer");
+                       ret = LTTNG_ERR_UNK;
+                       goto error;
+               }
+       }
+
        ret = LTTNG_OK;
 
 error:
@@ -2561,9 +2725,11 @@ 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;
 
        assert(session);
 
+       DBG("Begin stop session %s (id %" PRIu64 ")", session->name, session->id);
        /* Short cut */
        ksession = session->kernel_session;
        usess = session->ust_session;
@@ -2574,6 +2740,32 @@ int cmd_stop_trace(struct ltt_session *session)
                goto error;
        }
 
+       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);
+               }
+       }
+
+       /*
+        * 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;
+               }
+       }
+
        /* Kernel tracer */
        if (ksession && ksession->active) {
                DBG("Stop kernel tracing");
@@ -2603,6 +2795,8 @@ int cmd_stop_trace(struct ltt_session *session)
                }
 
                ksession->active = 0;
+               DBG("Kernel session stopped %s (id %" PRIu64 ")", session->name,
+                               session->id);
        }
 
        if (usess && usess->active) {
@@ -2621,7 +2815,7 @@ int cmd_stop_trace(struct ltt_session *session)
 
        /* Flag inactive after a successful stop. */
        session->active = 0;
-       ret = LTTNG_OK;
+       ret = !error_occured ? LTTNG_OK : LTTNG_ERR_UNK;
 
 error:
        return ret;
@@ -2845,7 +3039,8 @@ error:
  *
  * Called with session lock held.
  */
-int cmd_destroy_session(struct ltt_session *session, int wpipe)
+int cmd_destroy_session(struct ltt_session *session, int wpipe,
+               struct notification_thread_handle *notification_thread_handle)
 {
        int ret;
        struct ltt_ust_session *usess;
@@ -2857,6 +3052,37 @@ int cmd_destroy_session(struct ltt_session *session, int wpipe)
        usess = session->ust_session;
        ksess = session->kernel_session;
 
+       DBG("Begin destroy session %s (id %" PRIu64 ")", session->name, session->id);
+
+       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->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) {
+               unsubscribe_session_consumed_size_rotation(session, notification_thread_handle);
+               session->rotate_size = 0;
+       }
+
+       /*
+        * The rename of the current chunk is performed at stop, but if we rotated
+        * the session after the previous stop command, we need to rename the
+        * new (and empty) chunk that was started in between.
+        */
+       if (session->rotated_after_last_stop) {
+               rename_active_chunk(session);
+       }
+
        /* Clean kernel session teardown */
        kernel_destroy_session(ksess);
 
@@ -2884,6 +3110,59 @@ int cmd_destroy_session(struct ltt_session *session, int wpipe)
                PERROR("write kernel poll pipe");
        }
 
+       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);
+       }
        ret = session_destroy(session);
 
        return ret;
@@ -3234,6 +3513,8 @@ int cmd_data_pending(struct ltt_session *session)
 
        assert(session);
 
+       DBG("Data pending for session %s", session->name);
+
        /* Session MUST be stopped to ask for data availability. */
        if (session->active) {
                ret = LTTNG_ERR_SESSION_STARTED;
@@ -3255,6 +3536,13 @@ int cmd_data_pending(struct ltt_session *session)
                }
        }
 
+       /* 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;
+       }
+
        if (ksess && ksess->consumer) {
                ret = consumer_is_data_pending(ksess->id, ksess->consumer);
                if (ret == 1) {
@@ -3527,10 +3815,12 @@ 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;
        }
 
@@ -4225,6 +4515,558 @@ int cmd_set_session_shm_path(struct ltt_session *session,
        return 0;
 }
 
+/*
+ * Command LTTNG_ROTATE_SESSION from the lttng-ctl library.
+ *
+ * Ask the consumer to rotate the session output directory.
+ * The session lock must be held.
+ *
+ * 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;
+       /*
+        * 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) {
+               cmd_ret = LTTNG_ERR_START_SESSION_ONCE;
+               goto end;
+       }
+
+       if (session->live_timer || session->snapshot_mode ||
+                       !session->output_traces) {
+               cmd_ret = LTTNG_ERR_ROTATION_NOT_AVAILABLE;
+               goto end;
+       }
+
+       /*
+        * Unsupported feature in lttng-relayd before 2.11.
+        */
+       if (session->consumer->type == CONSUMER_DST_NET &&
+                       (session->consumer->relay_major_version == 2 &&
+                       session->consumer->relay_minor_version < 11)) {
+               cmd_ret = LTTNG_ERR_ROTATION_NOT_AVAILABLE_RELAY;
+               goto end;
+       }
+
+       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;
+       }
+
+       /*
+        * After a stop, we only allow one rotation to occur, the other ones are
+        * useless until a new start.
+        */
+       if (session->rotated_after_last_stop) {
+               DBG("Session \"%s\" was already rotated after stop, refusing rotation",
+                               session->name);
+               cmd_ret = LTTNG_ERR_ROTATION_MULTIPLE_AFTER_STOP;
+               goto end;
+       }
+
+       /* Special case for the first rotation. */
+       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. */
+               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");
+                       cmd_ret = LTTNG_ERR_UNK;
+                       goto end;
+               }
+       } else {
+               /*
+                * The currently active tracing path is now the folder we
+                * want to rotate.
+                */
+               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 the active tracing path to the current rotate path");
+                       cmd_ret = LTTNG_ERR_UNK;
+                       goto end;
+               }
+       }
+       DBG("Current rotate path %s", session->rotation_chunk.current_rotate_path);
+
+       /*
+        * Channels created after this point will belong to the next
+        * archive id.
+        */
+       session->current_archive_id++;
+
+       now = time(NULL);
+       if (now == (time_t) -1) {
+               cmd_ret = LTTNG_ERR_ROTATION_NOT_AVAILABLE;
+               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");
+               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");
+               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.
+                * Ex: ~/lttng-traces/auto-20170922-111748/20170922-111754-42
+                */
+               ret = snprintf(session->rotation_chunk.active_tracing_path,
+                               sizeof(session->rotation_chunk.active_tracing_path),
+                               "%s/%s-%" PRIu64,
+                               session_get_base_path(session),
+                               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");
+                       cmd_ret = LTTNG_ERR_UNK;
+                       goto error;
+               }
+               /*
+                * The sub-directory for the consumer
+                * Ex: /20170922-111754-42/kernel
+                */
+               ret = snprintf(session->kernel_session->consumer->chunk_path,
+                               sizeof(session->kernel_session->consumer->chunk_path),
+                               "/%s-%" PRIu64, datetime,
+                               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");
+                       cmd_ret = LTTNG_ERR_UNK;
+                       goto error;
+               }
+               /*
+                * Create the new chunk folder, before the rotation begins so we don't
+                * race with the consumer/tracer activity.
+                */
+               ret = domain_mkdir(session->kernel_session->consumer, session,
+                               session->kernel_session->uid,
+                               session->kernel_session->gid);
+               if (ret) {
+                       ERR("Failed to create kernel session tracing path at %s",
+                                       session->kernel_session->consumer->chunk_path);
+                       cmd_ret = LTTNG_ERR_CREATE_DIR_FAIL;
+                       goto error;
+               }
+               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->current_archive_id + 1);
+               if (ret < 0) {
+                       ERR("Failed to format active UST tracing path in rotate session command");
+                       cmd_ret = LTTNG_ERR_UNK;
+                       goto error;
+               }
+               ret = snprintf(session->ust_session->consumer->chunk_path,
+                               PATH_MAX, "/%s-%" PRIu64, datetime,
+                               session->current_archive_id + 1);
+               if (ret < 0) {
+                       ERR("Failed to format the UST consumer's sub-directory in rotate session command");
+                       cmd_ret = LTTNG_ERR_UNK;
+                       goto error;
+               }
+               /*
+                * Create the new chunk folder, before the rotation begins so we don't
+                * race with the consumer/tracer activity.
+                */
+               ret = domain_mkdir(session->ust_session->consumer, session,
+                               session->ust_session->uid,
+                               session->ust_session->gid);
+               if (ret) {
+                       cmd_ret = LTTNG_ERR_CREATE_DIR_FAIL;
+                       goto error;
+               }
+               /*
+                * TODO: ust_app_rotate_session must be adapted to return
+                * an lttng_error_code, like its kernel counterpart.
+                */
+               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->current_archive_id;
+       }
+
+       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;
+}
+
+/*
+ * Command LTTNG_ROTATION_GET_INFO from the lttng-ctl library.
+ *
+ * Check if the session has finished its rotation.
+ *
+ * Return 0 on success or else a LTTNG_ERR code.
+ */
+int cmd_rotate_get_info(struct ltt_session *session,
+               struct lttng_rotation_get_info_return *info_return,
+               uint64_t rotation_id)
+{
+       int ret;
+
+       assert(session);
+
+       DBG("Cmd rotate_get_info session %s, rotation id %" PRIu64, session->name,
+                       session->current_archive_id);
+
+       if (session->current_archive_id != rotation_id) {
+               info_return->status = (int32_t) LTTNG_ROTATION_STATE_EXPIRED;
+               ret = LTTNG_OK;
+               goto end;
+       }
+
+       switch (session->rotation_state) {
+       case LTTNG_ROTATION_STATE_ONGOING:
+               DBG("Reporting that rotation id %" PRIu64 " of session %s is still pending",
+                               rotation_id, session->name);
+               break;
+       case LTTNG_ROTATION_STATE_COMPLETED:
+       {
+               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,
+                               current_tracing_path_reply_len);
+               if (ret) {
+                       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);
+               break;
+       default:
+               abort();
+       }
+
+       info_return->status = (int32_t) session->rotation_state;
+       ret = LTTNG_OK;
+end:
+       return ret;
+}
+
+/*
+ * Command LTTNG_ROTATION_SET_SCHEDULE from the lttng-ctl library.
+ *
+ * Configure the automatic rotation parameters.
+ * '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 a positive LTTNG_ERR code.
+ */
+int cmd_rotation_set_schedule(struct ltt_session *session,
+               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);
+
+       DBG("Cmd rotate set schedule session %s", session->name);
+
+       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;
+       }
+
+       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;
+       }
+
+       /* 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;
+       }
+
+       /*
+        * 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;
+       }
+
+       /*
+        * 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;
+       }
+
+       /*
+        * 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;
+       }
+
+       *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 disable session rotation timer in ROTATION_SET_SCHEDULE command");
+                               ret = LTTNG_ERR_UNK;
+                               goto end;
+                       }
+               }
+               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;
+                       }
+               } else {
+                       ret = unsubscribe_session_consumed_size_rotation(session,
+                                       notification_thread_handle);
+                       if (ret) {
+                               ERR("Failed to disable consumed-size notification in ROTATION_SET_SCHEDULE command");
+                               ret = LTTNG_ERR_UNK;
+                               goto end;
+                       }
+
+               }
+               break;
+       default:
+               /* Would have been caught before. */
+               abort();
+       }
+
+       ret = LTTNG_OK;
+
+       goto end;
+
+end:
+       return ret;
+}
+
+/* Wait for a given path to be removed before continuing. */
+static enum lttng_error_code wait_on_path(void *path_data)
+{
+       const char *shm_path = path_data;
+
+       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 {
+                               DBG("shm path no longer exists, completing the destruction of session");
+                       }
+                       break;
+               } else {
+                       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;
+                       }
+               }
+               usleep(SESSION_DESTROY_SHM_PATH_CHECK_DELAY_US);
+       }
+       return LTTNG_OK;
+}
+
+/*
+ * 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;
+
+       current_completion_handler = NULL;
+       return handler;
+}
+
 /*
  * Init command subsystem.
  */
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