Add notification session rotation hooks
[lttng-tools.git] / src / bin / lttng-sessiond / cmd.c
index 375324aec870bea400ce620b95fe8603ed1357cd..7f05655ecd7371a60c6fc3b5b9e1bd9eef768f84 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 +38,7 @@
 #include <lttng/channel.h>
 #include <lttng/channel-internal.h>
 #include <lttng/rotate-internal.h>
+#include <lttng/location-internal.h>
 #include <common/string-utils/string-utils.h>
 
 #include "channel.h"
@@ -47,7 +49,7 @@
 #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 "rotate.h"
 #include "rotation-thread.h"
 #include "sessiond-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
@@ -917,8 +944,8 @@ 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)
@@ -1003,7 +1030,7 @@ 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) {
@@ -1013,7 +1040,7 @@ 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) {
@@ -1152,7 +1179,7 @@ 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 +1411,15 @@ 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;
@@ -2094,6 +2127,12 @@ 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);
@@ -2600,7 +2639,7 @@ int rename_active_chunk(struct ltt_session *session)
 {
        int ret;
 
-       session->rotate_count++;
+       session->current_archive_id++;
 
        /*
         * The currently active tracing path is now the folder we
@@ -2633,7 +2672,7 @@ int rename_active_chunk(struct ltt_session *session)
                goto end;
        }
 end:
-       session->rotate_count--;
+       session->current_archive_id--;
        return ret;
 }
 
@@ -2669,7 +2708,7 @@ int cmd_stop_trace(struct ltt_session *session)
                sessiond_rotate_timer_stop(session);
        }
 
-       if (session->rotate_count > 0 && !session->rotate_pending) {
+       if (session->current_archive_id > 0 && !session->rotate_pending) {
                ret = rename_active_chunk(session);
                if (ret) {
                        /*
@@ -2953,7 +2992,8 @@ 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;
@@ -2975,6 +3015,11 @@ int cmd_destroy_session(struct ltt_session *session, int wpipe)
                sessiond_rotate_timer_stop(session);
        }
 
+       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
@@ -3011,6 +3056,59 @@ 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;
@@ -3665,10 +3763,12 @@ 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;
        }
 
@@ -4400,7 +4500,7 @@ 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;
+               ret = -LTTNG_ERR_ROTATION_NOT_AVAILABLE_RELAY;
                goto end;
        }
 
@@ -4422,7 +4522,7 @@ int cmd_rotate_session(struct ltt_session *session,
        }
 
        /* Special case for the first rotation. */
-       if (session->rotate_count == 0) {
+       if (session->current_archive_id == 0) {
                const char *base_path = NULL;
 
                /* Either one of the two sessions is enough to get the root path. */
@@ -4458,9 +4558,17 @@ int cmd_rotate_session(struct ltt_session *session,
        }
        DBG("Current rotate path %s", session->rotation_chunk.current_rotate_path);
 
-       session->rotate_count++;
+       session->current_archive_id++;
        session->rotate_pending = true;
        session->rotation_state = LTTNG_ROTATION_STATE_ONGOING;
+       ret = notification_thread_command_session_rotation_ongoing(
+                       notification_thread_handle,
+                       session->name, session->uid, session->gid,
+                       session->current_archive_id);
+       if (ret != LTTNG_OK) {
+               ERR("Failed to notify notification thread that a session rotation is ongoing for session %s",
+                               session->name);
+       }
 
        /*
         * Create the path name for the next chunk.
@@ -4495,7 +4603,7 @@ 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;
@@ -4508,7 +4616,7 @@ 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;
@@ -4537,7 +4645,7 @@ int cmd_rotate_session(struct ltt_session *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;
@@ -4545,7 +4653,7 @@ int cmd_rotate_session(struct ltt_session *session,
                }
                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;
@@ -4558,9 +4666,12 @@ int cmd_rotate_session(struct ltt_session *session,
                ret = domain_mkdir(session->ust_session->consumer, 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) {
-                       ret = -LTTNG_ERR_CREATE_DIR_FAIL;
                        goto end;
                }
                /*
@@ -4570,13 +4681,29 @@ int cmd_rotate_session(struct ltt_session *session,
                 * session_list locks.
                 */
                if (!session->kernel_session && !ust_active) {
+                       struct lttng_trace_archive_location *location;
+
+                       session->rotate_pending = false;
+                       session->rotation_state = LTTNG_ROTATION_STATE_COMPLETED;
                        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;
+
+                       /* Ownership of location is transferred. */
+                       location = session_get_trace_archive_location(session);
+                       ret = notification_thread_command_session_rotation_completed(
+                                       notification_thread_handle,
+                                       session->name,
+                                       session->uid,
+                                       session->gid,
+                                       session->current_archive_id,
+                                       location);
+                       if (ret != LTTNG_OK) {
+                               ERR("Failed to notify notification thread that rotation is complete for session %s",
+                                               session->name);
+                       }
                }
        }
 
@@ -4585,11 +4712,11 @@ int cmd_rotate_session(struct ltt_session *session,
        }
 
        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);
+       DBG("Cmd rotate session %s, current_archive_id %" PRIu64 " sent",
+                       session->name, session->current_archive_id);
        ret = LTTNG_OK;
 
 end:
@@ -4612,9 +4739,9 @@ 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;
@@ -4626,16 +4753,59 @@ 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);
@@ -4654,14 +4824,19 @@ 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);
 
@@ -4669,42 +4844,117 @@ 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;
+       }
+
+       /* 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;
-       /* Trying to disable an inactive timer. */
-       } else if (timer_us == -1ULL && !session->rotate_timer_period) {
-               ret = LTTNG_ERR_ROTATION_NO_TIMER_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;
        }
 
-       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 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;
+       }
 
-               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);
+       /*
+        * 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 = sessiond_rotate_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 = sessiond_rotate_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;
+               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;
@@ -4730,7 +4980,7 @@ int cmd_session_get_current_output(struct ltt_session *session,
        const char *path;
 
        if (!session->snapshot_mode) {
-               if (session->rotate_count == 0) {
+               if (session->current_archive_id == 0) {
                        if (session->kernel_session) {
                                path = session_get_base_path(session);
                        } else if (session->ust_session) {
@@ -4767,6 +5017,49 @@ 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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