X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fcmd.c;h=e45d4423ac0e0a51b123f2c0275e13f981c9f763;hp=be493fd8a5527f7795446592016c44f47eaa6d09;hb=53fb6336415e5f19b6e8c4baeb0d0555ed5d6e66;hpb=433f5ba9ca8e445c979b49703ac195f77a94c684

diff --git a/src/bin/lttng-sessiond/cmd.c b/src/bin/lttng-sessiond/cmd.c
index be493fd8a..e45d4423a 100644
--- a/src/bin/lttng-sessiond/cmd.c
+++ b/src/bin/lttng-sessiond/cmd.c
@@ -1,21 +1,14 @@
 /*
- * Copyright (C) 2012 - David Goulet <dgoulet@efficios.com>
- * Copyright (C) 2016 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
+ * Copyright (C) 2012 David Goulet <dgoulet@efficios.com>
+ * Copyright (C) 2016 Jérémie Galarneau <jeremie.galarneau@efficios.com>
  *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License, version 2 only, as
- * published by the Free Software Foundation.
+ * SPDX-License-Identifier: GPL-2.0-only
  *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
- * more details.
- *
- * You should have received a copy of the GNU General Public License along with
- * this program; if not, write to the Free Software Foundation, Inc., 51
- * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include "bin/lttng-sessiond/tracker.h"
+#include "lttng/lttng-error.h"
+#include "lttng/tracker.h"
 #define _LGPL_SOURCE
 #include <assert.h>
 #include <inttypes.h>
@@ -998,6 +991,8 @@ static enum lttng_error_code create_connect_relayd(struct lttng_uri *uri,
 
 	/* Create socket for control stream. */
 	if (uri->stype == LTTNG_STREAM_CONTROL) {
+		uint64_t result_flags;
+
 		DBG3("Creating relayd stream socket from URI");
 
 		/* Check relayd version */
@@ -1012,6 +1007,16 @@ static enum lttng_error_code create_connect_relayd(struct lttng_uri *uri,
 		}
 		consumer->relay_major_version = rsock->major;
 		consumer->relay_minor_version = rsock->minor;
+		ret = relayd_get_configuration(rsock, 0,
+				&result_flags);
+		if (ret < 0) {
+			ERR("Unable to get relayd configuration");
+			status = LTTNG_ERR_RELAYD_CONNECT_FAIL;
+			goto close_sock;
+		}
+		if (result_flags & LTTCOMM_RELAYD_CONFIGURATION_FLAG_CLEAR_ALLOWED) {
+			consumer->relay_allows_clear = true;
+		}
 	} else if (uri->stype == LTTNG_STREAM_DATA) {
 		DBG3("Creating relayd data socket from URI");
 	} else {
@@ -1185,6 +1190,7 @@ int cmd_setup_relayd(struct ltt_session *session)
 
 	DBG("Setting relayd for session %s", session->name);
 
+	rcu_read_lock();
 	if (session->current_trace_chunk) {
 		enum lttng_trace_chunk_status status = lttng_trace_chunk_get_id(
 				session->current_trace_chunk, &current_chunk_id.value);
@@ -1198,8 +1204,6 @@ int cmd_setup_relayd(struct ltt_session *session)
 		}
 	}
 
-	rcu_read_lock();
-
 	if (usess && usess->consumer && usess->consumer->type == CONSUMER_DST_NET
 			&& usess->consumer->enabled) {
 		/* For each consumer socket, send relayd sockets */
@@ -1225,6 +1229,8 @@ int cmd_setup_relayd(struct ltt_session *session)
 			usess->consumer->relay_major_version;
 		session->consumer->relay_minor_version =
 			usess->consumer->relay_minor_version;
+		session->consumer->relay_allows_clear =
+			usess->consumer->relay_allows_clear;
 	}
 
 	if (ksess && ksess->consumer && ksess->consumer->type == CONSUMER_DST_NET
@@ -1251,6 +1257,8 @@ int cmd_setup_relayd(struct ltt_session *session)
 			ksess->consumer->relay_major_version;
 		session->consumer->relay_minor_version =
 			ksess->consumer->relay_minor_version;
+		session->consumer->relay_allows_clear =
+			ksess->consumer->relay_allows_clear;
 	}
 
 error:
@@ -1261,7 +1269,7 @@ error:
 /*
  * Start a kernel session by opening all necessary streams.
  */
-static int start_kernel_session(struct ltt_kernel_session *ksess)
+int start_kernel_session(struct ltt_kernel_session *ksess)
 {
 	int ret;
 	struct ltt_kernel_channel *kchan;
@@ -1323,133 +1331,71 @@ error:
 	return ret;
 }
 
-/*
- * Command LTTNG_DISABLE_CHANNEL processed by the client thread.
- */
-int cmd_disable_channel(struct ltt_session *session,
-		enum lttng_domain_type domain, char *channel_name)
+int stop_kernel_session(struct ltt_kernel_session *ksess)
 {
+	struct ltt_kernel_channel *kchan;
+	bool error_occurred = false;
 	int ret;
-	struct ltt_ust_session *usess;
-
-	usess = session->ust_session;
-
-	rcu_read_lock();
-
-	switch (domain) {
-	case LTTNG_DOMAIN_KERNEL:
-	{
-		ret = channel_kernel_disable(session->kernel_session,
-				channel_name);
-		if (ret != LTTNG_OK) {
-			goto error;
-		}
 
-		kernel_wait_quiescent();
-		break;
+	if (!ksess || !ksess->active) {
+		return LTTNG_OK;
 	}
-	case LTTNG_DOMAIN_UST:
-	{
-		struct ltt_ust_channel *uchan;
-		struct lttng_ht *chan_ht;
-
-		chan_ht = usess->domain_global.channels;
-
-		uchan = trace_ust_find_channel_by_name(chan_ht, channel_name);
-		if (uchan == NULL) {
-			ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
-			goto error;
-		}
+	DBG("Stopping kernel tracing");
 
-		ret = channel_ust_disable(usess, uchan);
-		if (ret != LTTNG_OK) {
-			goto error;
-		}
-		break;
-	}
-	default:
-		ret = LTTNG_ERR_UNKNOWN_DOMAIN;
+	ret = kernel_stop_session(ksess);
+	if (ret < 0) {
+		ret = LTTNG_ERR_KERN_STOP_FAIL;
 		goto error;
 	}
 
-	ret = LTTNG_OK;
-
-error:
-	rcu_read_unlock();
-	return ret;
-}
-
-/*
- * Command LTTNG_TRACK_PID processed by the client thread.
- *
- * Called with session lock held.
- */
-int cmd_track_pid(struct ltt_session *session, enum lttng_domain_type domain,
-		int pid)
-{
-	int ret;
-
-	rcu_read_lock();
-
-	switch (domain) {
-	case LTTNG_DOMAIN_KERNEL:
-	{
-		struct ltt_kernel_session *ksess;
-
-		ksess = session->kernel_session;
+	kernel_wait_quiescent();
 
-		ret = kernel_track_pid(ksess, pid);
-		if (ret != LTTNG_OK) {
-			goto error;
+	/* Flush metadata after stopping (if exists) */
+	if (ksess->metadata_stream_fd >= 0) {
+		ret = kernel_metadata_flush_buffer(ksess->metadata_stream_fd);
+		if (ret < 0) {
+			ERR("Kernel metadata flush failed");
+			error_occurred = true;
 		}
-
-		kernel_wait_quiescent();
-		break;
 	}
-	case LTTNG_DOMAIN_UST:
-	{
-		struct ltt_ust_session *usess;
-
-		usess = session->ust_session;
 
-		ret = trace_ust_track_pid(usess, pid);
-		if (ret != LTTNG_OK) {
-			goto error;
+	/* Flush all buffers after stopping */
+	cds_list_for_each_entry(kchan, &ksess->channel_list.head, list) {
+		ret = kernel_flush_buffer(kchan);
+		if (ret < 0) {
+			ERR("Kernel flush buffer error");
+			error_occurred = true;
 		}
-		break;
-	}
-	default:
-		ret = LTTNG_ERR_UNKNOWN_DOMAIN;
-		goto error;
 	}
 
-	ret = LTTNG_OK;
-
+	ksess->active = 0;
+	if (error_occurred) {
+		ret = LTTNG_ERR_UNK;
+	} else {
+		ret = LTTNG_OK;
+	}
 error:
-	rcu_read_unlock();
 	return ret;
 }
 
 /*
- * Command LTTNG_UNTRACK_PID processed by the client thread.
- *
- * Called with session lock held.
+ * Command LTTNG_DISABLE_CHANNEL processed by the client thread.
  */
-int cmd_untrack_pid(struct ltt_session *session, enum lttng_domain_type domain,
-		int pid)
+int cmd_disable_channel(struct ltt_session *session,
+		enum lttng_domain_type domain, char *channel_name)
 {
 	int ret;
+	struct ltt_ust_session *usess;
+
+	usess = session->ust_session;
 
 	rcu_read_lock();
 
 	switch (domain) {
 	case LTTNG_DOMAIN_KERNEL:
 	{
-		struct ltt_kernel_session *ksess;
-
-		ksess = session->kernel_session;
-
-		ret = kernel_untrack_pid(ksess, pid);
+		ret = channel_kernel_disable(session->kernel_session,
+				channel_name);
 		if (ret != LTTNG_OK) {
 			goto error;
 		}
@@ -1459,11 +1405,18 @@ int cmd_untrack_pid(struct ltt_session *session, enum lttng_domain_type domain,
 	}
 	case LTTNG_DOMAIN_UST:
 	{
-		struct ltt_ust_session *usess;
+		struct ltt_ust_channel *uchan;
+		struct lttng_ht *chan_ht;
 
-		usess = session->ust_session;
+		chan_ht = usess->domain_global.channels;
+
+		uchan = trace_ust_find_channel_by_name(chan_ht, channel_name);
+		if (uchan == NULL) {
+			ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+			goto error;
+		}
 
-		ret = trace_ust_untrack_pid(usess, pid);
+		ret = channel_ust_disable(usess, uchan);
 		if (ret != LTTNG_OK) {
 			goto error;
 		}
@@ -1652,6 +1605,211 @@ end:
 	return ret;
 }
 
+enum lttng_error_code cmd_process_attr_tracker_get_tracking_policy(
+		struct ltt_session *session,
+		enum lttng_domain_type domain,
+		enum lttng_process_attr process_attr,
+		enum lttng_tracking_policy *policy)
+{
+	enum lttng_error_code ret_code = LTTNG_OK;
+	const struct process_attr_tracker *tracker;
+
+	switch (domain) {
+	case LTTNG_DOMAIN_KERNEL:
+		if (!session->kernel_session) {
+			ret_code = LTTNG_ERR_INVALID;
+			goto end;
+		}
+		tracker = kernel_get_process_attr_tracker(
+				session->kernel_session, process_attr);
+		break;
+	case LTTNG_DOMAIN_UST:
+		if (!session->ust_session) {
+			ret_code = LTTNG_ERR_INVALID;
+			goto end;
+		}
+		tracker = trace_ust_get_process_attr_tracker(
+				session->ust_session, process_attr);
+		break;
+	default:
+		ret_code = LTTNG_ERR_UNSUPPORTED_DOMAIN;
+		goto end;
+	}
+	if (tracker) {
+		*policy = process_attr_tracker_get_tracking_policy(tracker);
+	} else {
+		ret_code = LTTNG_ERR_INVALID;
+	}
+end:
+	return ret_code;
+}
+
+enum lttng_error_code cmd_process_attr_tracker_set_tracking_policy(
+		struct ltt_session *session,
+		enum lttng_domain_type domain,
+		enum lttng_process_attr process_attr,
+		enum lttng_tracking_policy policy)
+{
+	enum lttng_error_code ret_code = LTTNG_OK;
+
+	switch (policy) {
+	case LTTNG_TRACKING_POLICY_INCLUDE_SET:
+	case LTTNG_TRACKING_POLICY_EXCLUDE_ALL:
+	case LTTNG_TRACKING_POLICY_INCLUDE_ALL:
+		break;
+	default:
+		ret_code = LTTNG_ERR_INVALID;
+		goto end;
+	}
+
+	switch (domain) {
+	case LTTNG_DOMAIN_KERNEL:
+		if (!session->kernel_session) {
+			ret_code = LTTNG_ERR_INVALID;
+			goto end;
+		}
+		ret_code = kernel_process_attr_tracker_set_tracking_policy(
+				session->kernel_session, process_attr, policy);
+		break;
+	case LTTNG_DOMAIN_UST:
+		if (!session->ust_session) {
+			ret_code = LTTNG_ERR_INVALID;
+			goto end;
+		}
+		ret_code = trace_ust_process_attr_tracker_set_tracking_policy(
+				session->ust_session, process_attr, policy);
+		break;
+	default:
+		ret_code = LTTNG_ERR_UNSUPPORTED_DOMAIN;
+		break;
+	}
+end:
+	return ret_code;
+}
+
+enum lttng_error_code cmd_process_attr_tracker_inclusion_set_add_value(
+		struct ltt_session *session,
+		enum lttng_domain_type domain,
+		enum lttng_process_attr process_attr,
+		const struct process_attr_value *value)
+{
+	enum lttng_error_code ret_code = LTTNG_OK;
+
+	switch (domain) {
+	case LTTNG_DOMAIN_KERNEL:
+		if (!session->kernel_session) {
+			ret_code = LTTNG_ERR_INVALID;
+			goto end;
+		}
+		ret_code = kernel_process_attr_tracker_inclusion_set_add_value(
+				session->kernel_session, process_attr, value);
+		break;
+	case LTTNG_DOMAIN_UST:
+		if (!session->ust_session) {
+			ret_code = LTTNG_ERR_INVALID;
+			goto end;
+		}
+		ret_code = trace_ust_process_attr_tracker_inclusion_set_add_value(
+				session->ust_session, process_attr, value);
+		break;
+	default:
+		ret_code = LTTNG_ERR_UNSUPPORTED_DOMAIN;
+		break;
+	}
+end:
+	return ret_code;
+}
+
+enum lttng_error_code cmd_process_attr_tracker_inclusion_set_remove_value(
+		struct ltt_session *session,
+		enum lttng_domain_type domain,
+		enum lttng_process_attr process_attr,
+		const struct process_attr_value *value)
+{
+	enum lttng_error_code ret_code = LTTNG_OK;
+
+	switch (domain) {
+	case LTTNG_DOMAIN_KERNEL:
+		if (!session->kernel_session) {
+			ret_code = LTTNG_ERR_INVALID;
+			goto end;
+		}
+		ret_code = kernel_process_attr_tracker_inclusion_set_remove_value(
+				session->kernel_session, process_attr, value);
+		break;
+	case LTTNG_DOMAIN_UST:
+		if (!session->ust_session) {
+			ret_code = LTTNG_ERR_INVALID;
+			goto end;
+		}
+		ret_code = trace_ust_process_attr_tracker_inclusion_set_remove_value(
+				session->ust_session, process_attr, value);
+		break;
+	default:
+		ret_code = LTTNG_ERR_UNSUPPORTED_DOMAIN;
+		break;
+	}
+end:
+	return ret_code;
+}
+
+enum lttng_error_code cmd_process_attr_tracker_get_inclusion_set(
+		struct ltt_session *session,
+		enum lttng_domain_type domain,
+		enum lttng_process_attr process_attr,
+		struct lttng_process_attr_values **values)
+{
+	enum lttng_error_code ret_code = LTTNG_OK;
+	const struct process_attr_tracker *tracker;
+	enum process_attr_tracker_status status;
+
+	switch (domain) {
+	case LTTNG_DOMAIN_KERNEL:
+		if (!session->kernel_session) {
+			ret_code = LTTNG_ERR_INVALID;
+			goto end;
+		}
+		tracker = kernel_get_process_attr_tracker(
+				session->kernel_session, process_attr);
+		break;
+	case LTTNG_DOMAIN_UST:
+		if (!session->ust_session) {
+			ret_code = LTTNG_ERR_INVALID;
+			goto end;
+		}
+		tracker = trace_ust_get_process_attr_tracker(
+				session->ust_session, process_attr);
+		break;
+	default:
+		ret_code = LTTNG_ERR_UNSUPPORTED_DOMAIN;
+		goto end;
+	}
+
+	if (!tracker) {
+		ret_code = LTTNG_ERR_INVALID;
+		goto end;
+	}
+
+	status = process_attr_tracker_get_inclusion_set(tracker, values);
+	switch (status) {
+	case PROCESS_ATTR_TRACKER_STATUS_OK:
+		ret_code = LTTNG_OK;
+		break;
+	case PROCESS_ATTR_TRACKER_STATUS_INVALID_TRACKING_POLICY:
+		ret_code = LTTNG_ERR_PROCESS_ATTR_TRACKER_INVALID_TRACKING_POLICY;
+		break;
+	case PROCESS_ATTR_TRACKER_STATUS_ERROR:
+		ret_code = LTTNG_ERR_NOMEM;
+		break;
+	default:
+		ret_code = LTTNG_ERR_UNK;
+		break;
+	}
+
+end:
+	return ret_code;
+}
+
 /*
  * Command LTTNG_DISABLE_EVENT processed by the client thread.
  */
@@ -2510,57 +2668,6 @@ ssize_t cmd_list_syscalls(struct lttng_event **events)
 	return syscall_table_list(events);
 }
 
-/*
- * Command LTTNG_LIST_TRACKER_PIDS processed by the client thread.
- *
- * Called with session lock held.
- */
-ssize_t cmd_list_tracker_pids(struct ltt_session *session,
-		enum lttng_domain_type domain, int32_t **pids)
-{
-	int ret;
-	ssize_t nr_pids = 0;
-
-	switch (domain) {
-	case LTTNG_DOMAIN_KERNEL:
-	{
-		struct ltt_kernel_session *ksess;
-
-		ksess = session->kernel_session;
-		nr_pids = kernel_list_tracker_pids(ksess, pids);
-		if (nr_pids < 0) {
-			ret = LTTNG_ERR_KERN_LIST_FAIL;
-			goto error;
-		}
-		break;
-	}
-	case LTTNG_DOMAIN_UST:
-	{
-		struct ltt_ust_session *usess;
-
-		usess = session->ust_session;
-		nr_pids = trace_ust_list_tracker_pids(usess, pids);
-		if (nr_pids < 0) {
-			ret = LTTNG_ERR_UST_LIST_FAIL;
-			goto error;
-		}
-		break;
-	}
-	case LTTNG_DOMAIN_LOG4J:
-	case LTTNG_DOMAIN_JUL:
-	case LTTNG_DOMAIN_PYTHON:
-	default:
-		ret = LTTNG_ERR_UND;
-		goto error;
-	}
-
-	return nr_pids;
-
-error:
-	/* Return negative value to differentiate return code */
-	return -ret;
-}
-
 /*
  * Command LTTNG_START_TRACE processed by the client thread.
  *
@@ -2572,6 +2679,10 @@ int cmd_start_trace(struct ltt_session *session)
 	unsigned long nb_chan = 0;
 	struct ltt_kernel_session *ksession;
 	struct ltt_ust_session *usess;
+	const bool session_rotated_after_last_stop =
+			session->rotated_after_last_stop;
+	const bool session_cleared_after_last_stop =
+			session->cleared_after_last_stop;
 
 	assert(session);
 
@@ -2582,6 +2693,23 @@ int cmd_start_trace(struct ltt_session *session)
 	/* Is the session already started? */
 	if (session->active) {
 		ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
+		/* Perform nothing */
+		goto end;
+	}
+
+	if (session->rotation_state == LTTNG_ROTATION_STATE_ONGOING &&
+			!session->current_trace_chunk) {
+		/*
+		 * A rotation was launched while the session was stopped and
+		 * it has not been completed yet. It is not possible to start
+		 * the session since starting the session here would require a
+		 * rotation from "NULL" to a new trace chunk. That rotation
+		 * would overlap with the ongoing rotation, which is not
+		 * supported.
+		 */
+		WARN("Refusing to start session \"%s\" as a rotation launched after the last \"stop\" is still ongoing",
+				session->name);
+		ret = LTTNG_ERR_ROTATION_PENDING;
 		goto error;
 	}
 
@@ -2600,21 +2728,47 @@ int cmd_start_trace(struct ltt_session *session)
 		goto error;
 	}
 
+	session->active = 1;
+	session->rotated_after_last_stop = false;
+	session->cleared_after_last_stop = false;
 	if (session->output_traces && !session->current_trace_chunk) {
-		struct lttng_trace_chunk *trace_chunk;
+		if (!session->has_been_started) {
+			struct lttng_trace_chunk *trace_chunk;
 
-		trace_chunk = session_create_new_trace_chunk(
-				session, NULL, NULL, NULL);
-		if (!trace_chunk) {
-			ret = LTTNG_ERR_CREATE_DIR_FAIL;
-			goto error;
-		}
-		assert(!session->current_trace_chunk);
-		ret = session_set_trace_chunk(session, trace_chunk, NULL);
-		lttng_trace_chunk_put(trace_chunk);
-		if (ret) {
-			ret = LTTNG_ERR_CREATE_TRACE_CHUNK_FAIL_CONSUMER;
-			goto error;
+			DBG("Creating initial trace chunk of session \"%s\"",
+					session->name);
+			trace_chunk = session_create_new_trace_chunk(
+					session, NULL, NULL, NULL);
+			if (!trace_chunk) {
+				ret = LTTNG_ERR_CREATE_DIR_FAIL;
+				goto error;
+			}
+			assert(!session->current_trace_chunk);
+			ret = session_set_trace_chunk(session, trace_chunk,
+					NULL);
+			lttng_trace_chunk_put(trace_chunk);
+			if (ret) {
+				ret = LTTNG_ERR_CREATE_TRACE_CHUNK_FAIL_CONSUMER;
+				goto error;
+			}
+		} else {
+			DBG("Rotating session \"%s\" from its current \"NULL\" trace chunk to a new chunk",
+					session->name);
+			/*
+			 * Rotate existing streams into the new chunk.
+			 * This is a "quiet" rotation has no client has
+			 * explicitly requested this operation.
+			 *
+			 * There is also no need to wait for the rotation
+			 * to complete as it will happen immediately. No data
+			 * was produced as the session was stopped, so the
+			 * rotation should happen on reception of the command.
+			 */
+			ret = cmd_rotate_session(session, NULL, true,
+					LTTNG_TRACE_CHUNK_COMMAND_TYPE_NO_OPERATION);
+			if (ret != LTTNG_OK) {
+				goto error;
+			}
 		}
 	}
 
@@ -2637,10 +2791,6 @@ int cmd_start_trace(struct ltt_session *session)
 		}
 	}
 
-	/* Flag this after a successful start. */
-	session->has_been_started = 1;
-	session->active = 1;
-
 	/*
 	 * Clear the flag that indicates that a rotation was done while the
 	 * session was stopped.
@@ -2661,6 +2811,18 @@ int cmd_start_trace(struct ltt_session *session)
 	ret = LTTNG_OK;
 
 error:
+	if (ret == LTTNG_OK) {
+		/* Flag this after a successful start. */
+		session->has_been_started |= 1;
+	} else {
+		session->active = 0;
+		/* Restore initial state on error. */
+		session->rotated_after_last_stop =
+				session_rotated_after_last_stop;
+		session->cleared_after_last_stop =
+				session_cleared_after_last_stop;
+	}
+end:
 	return ret;
 }
 
@@ -2670,14 +2832,12 @@ error:
 int cmd_stop_trace(struct ltt_session *session)
 {
 	int ret;
-	struct ltt_kernel_channel *kchan;
 	struct ltt_kernel_session *ksession;
 	struct ltt_ust_session *usess;
-	bool error_occurred = false;
 
 	assert(session);
 
-	DBG("Begin stop session %s (id %" PRIu64 ")", session->name, session->id);
+	DBG("Begin stop session \"%s\" (id %" PRIu64 ")", session->name, session->id);
 	/* Short cut */
 	ksession = session->kernel_session;
 	usess = session->ust_session;
@@ -2688,39 +2848,9 @@ int cmd_stop_trace(struct ltt_session *session)
 		goto error;
 	}
 
-	/* Kernel tracer */
-	if (ksession && ksession->active) {
-		DBG("Stop kernel tracing");
-
-		ret = kernel_stop_session(ksession);
-		if (ret < 0) {
-			ret = LTTNG_ERR_KERN_STOP_FAIL;
-			goto error;
-		}
-
-		kernel_wait_quiescent();
-
-		/* Flush metadata after stopping (if exists) */
-		if (ksession->metadata_stream_fd >= 0) {
-			ret = kernel_metadata_flush_buffer(ksession->metadata_stream_fd);
-			if (ret < 0) {
-				ERR("Kernel metadata flush failed");
-				error_occurred = true;
-			}
-		}
-
-		/* Flush all buffers after stopping */
-		cds_list_for_each_entry(kchan, &ksession->channel_list.head, list) {
-			ret = kernel_flush_buffer(kchan);
-			if (ret < 0) {
-				ERR("Kernel flush buffer error");
-				error_occurred = true;
-			}
-		}
-
-		ksession->active = 0;
-		DBG("Kernel session stopped %s (id %" PRIu64 ")", session->name,
-				session->id);
+	ret = stop_kernel_session(ksession);
+	if (ret != LTTNG_OK) {
+		goto error;
 	}
 
 	if (usess && usess->active) {
@@ -2731,9 +2861,11 @@ int cmd_stop_trace(struct ltt_session *session)
 		}
 	}
 
+	DBG("Completed stop session \"%s\" (id %" PRIu64 ")", session->name,
+			session->id);
 	/* Flag inactive after a successful stop. */
 	session->active = 0;
-	ret = !error_occurred ? LTTNG_OK : LTTNG_ERR_UNK;
+	ret = LTTNG_OK;
 
 error:
 	return ret;
@@ -3243,14 +3375,13 @@ int cmd_destroy_session(struct ltt_session *session,
 		session->rotate_size = 0;
 	}
 
-	if (session->most_recent_chunk_id.is_set &&
-			session->most_recent_chunk_id.value != 0 &&
-			session->current_trace_chunk && session->output_traces) {
+	if (session->rotated && session->current_trace_chunk && session->output_traces) {
 		/*
 		 * Perform a last rotation on destruction if rotations have
 		 * occurred during the session's lifetime.
 		 */
-		ret = cmd_rotate_session(session, NULL, false);
+		ret = cmd_rotate_session(session, NULL, false,
+			LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED);
 		if (ret != LTTNG_OK) {
 			ERR("Failed to perform an implicit rotation as part of the destruction of session \"%s\": %s",
 					session->name, lttng_strerror(-ret));
@@ -3269,10 +3400,19 @@ int cmd_destroy_session(struct ltt_session *session,
 		 * emitted and no renaming of the current trace chunk takes
 		 * place.
 		 */
-		ret = cmd_rotate_session(session, NULL, true);
-		if (ret != LTTNG_OK) {
+		ret = cmd_rotate_session(session, NULL, true,
+			LTTNG_TRACE_CHUNK_COMMAND_TYPE_NO_OPERATION);
+		/*
+		 * Rotation operations may not be supported by the kernel
+		 * tracer. Hence, do not consider this implicit rotation as
+		 * a session destruction error. The library has already stopped
+		 * the session and waited for pending data; there is nothing
+		 * left to do but complete the destruction of the session.
+		 */
+		if (ret != LTTNG_OK &&
+				ret != -LTTNG_ERR_ROTATION_NOT_AVAILABLE_KERNEL) {
 			ERR("Failed to perform a quiet rotation as part of the destruction of session \"%s\": %s",
-					session->name, lttng_strerror(-ret));
+			    session->name, lttng_strerror(ret));
 			destruction_last_error = -ret;
 		}
 	}
@@ -4494,7 +4634,7 @@ int64_t get_session_nb_packets_per_stream(const struct ltt_session *session,
 		}
 		cur_nb_packets++;
 	}
-	if (!cur_nb_packets) {
+	if (!cur_nb_packets && size_left != max_size) {
 		/* Not enough room to grab one packet of each stream, error. */
 		return -1;
 	}
@@ -4607,7 +4747,7 @@ enum lttng_error_code snapshot_record(struct ltt_session *session,
 			snapshot_output->max_size);
 	if (nb_packets_per_stream < 0) {
 		ret_code = LTTNG_ERR_MAX_SIZE_INVALID;
-		goto error;
+		goto error_close_trace_chunk;
 	}
 
 	if (session->kernel_session) {
@@ -4615,7 +4755,7 @@ enum lttng_error_code snapshot_record(struct ltt_session *session,
 				snapshot_kernel_consumer_output, session,
 				wait, nb_packets_per_stream);
 		if (ret_code != LTTNG_OK) {
-			goto error;
+			goto error_close_trace_chunk;
 		}
 	}
 
@@ -4624,12 +4764,19 @@ enum lttng_error_code snapshot_record(struct ltt_session *session,
 				snapshot_ust_consumer_output, session,
 				wait, nb_packets_per_stream);
 		if (ret_code != LTTNG_OK) {
-			goto error;
+			goto error_close_trace_chunk;
 		}
 	}
 
-	if (session_close_trace_chunk(
-			    session, session->current_trace_chunk, NULL, NULL)) {
+error_close_trace_chunk:
+	if (session_set_trace_chunk(session, NULL, &snapshot_trace_chunk)) {
+		ERR("Failed to release the current trace chunk of session \"%s\"",
+				session->name);
+		ret_code = LTTNG_ERR_UNK;
+	}
+
+	if (session_close_trace_chunk(session, snapshot_trace_chunk,
+			LTTNG_TRACE_CHUNK_COMMAND_TYPE_NO_OPERATION, NULL)) {
 		/*
 		 * Don't goto end; make sure the chunk is closed for the session
 		 * to allow future snapshots.
@@ -4638,11 +4785,6 @@ enum lttng_error_code snapshot_record(struct ltt_session *session,
 				session->name);
 		ret_code = LTTNG_ERR_CLOSE_TRACE_CHUNK_FAIL_CONSUMER;
 	}
-	if (session_set_trace_chunk(session, NULL, NULL)) {
-		ERR("Failed to release the current trace chunk of session \"%s\"",
-				session->name);
-		ret_code = LTTNG_ERR_UNK;
-	}
 error:
 	if (original_ust_consumer_output) {
 		session->ust_session->consumer = original_ust_consumer_output;
@@ -4823,7 +4965,8 @@ int cmd_set_session_shm_path(struct ltt_session *session,
  */
 int cmd_rotate_session(struct ltt_session *session,
 		struct lttng_rotate_session_return *rotate_return,
-		bool quiet_rotation)
+		bool quiet_rotation,
+		enum lttng_trace_chunk_command_type command)
 {
 	int ret;
 	uint64_t ongoing_rotation_chunk_id;
@@ -4861,6 +5004,12 @@ int cmd_rotate_session(struct ltt_session *session,
 		goto end;
 	}
 
+	/* Unsupported feature in lttng-modules before 2.8 (lack of sequence number). */
+	if (session->kernel_session && !kernel_supports_ring_buffer_packet_sequence_number()) {
+		cmd_ret = LTTNG_ERR_ROTATION_NOT_AVAILABLE_KERNEL;
+		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);
@@ -4879,7 +5028,16 @@ int cmd_rotate_session(struct ltt_session *session,
 		goto end;
 	}
 
-	session->rotation_state = LTTNG_ROTATION_STATE_ONGOING;
+	/*
+	 * After a stop followed by a clear, disallow following rotations a they would
+	 * generate empty chunks.
+	 */
+	if (session->cleared_after_last_stop) {
+		DBG("Session \"%s\" was already cleared after stop, refusing rotation",
+				session->name);
+		cmd_ret = LTTNG_ERR_ROTATION_AFTER_STOP_CLEAR;
+		goto end;
+	}
 
 	if (session->active) {
 		new_trace_chunk = session_create_new_trace_chunk(session, NULL,
@@ -4904,11 +5062,6 @@ int cmd_rotate_session(struct ltt_session *session,
 		goto error;
 	}
 
-	assert(chunk_being_archived);
-	chunk_status = lttng_trace_chunk_get_id(chunk_being_archived,
-			&ongoing_rotation_chunk_id);
-	assert(chunk_status == LTTNG_TRACE_CHUNK_STATUS_OK);
-
 	if (session->kernel_session) {
 		cmd_ret = kernel_rotate_session(session);
 		if (cmd_ret != LTTNG_OK) {
@@ -4924,12 +5077,28 @@ int cmd_rotate_session(struct ltt_session *session,
 		}
 	}
 
+	if (!session->active) {
+		session->rotated_after_last_stop = true;
+	}
+
+	if (!chunk_being_archived) {
+		DBG("Rotating session \"%s\" from a \"NULL\" trace chunk to a new trace chunk, skipping completion check",
+				session->name);
+		if (failed_to_rotate) {
+			cmd_ret = rotation_fail_code;
+			goto error;
+		}
+		cmd_ret = LTTNG_OK;
+		goto end;
+	}
+
+	session->rotation_state = LTTNG_ROTATION_STATE_ONGOING;
+	chunk_status = lttng_trace_chunk_get_id(chunk_being_archived,
+			&ongoing_rotation_chunk_id);
+	assert(chunk_status == LTTNG_TRACE_CHUNK_STATUS_OK);
+
 	ret = session_close_trace_chunk(session, chunk_being_archived,
-			quiet_rotation ?
-					NULL :
-					&((enum lttng_trace_chunk_command_type){
-							LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED}),
-			session->last_chunk_path);
+		command, session->last_chunk_path);
 	if (ret) {
 		cmd_ret = LTTNG_ERR_CLOSE_TRACE_CHUNK_FAIL_CONSUMER;
 		goto error;
@@ -4948,10 +5117,6 @@ int cmd_rotate_session(struct ltt_session *session,
 		goto error;
 	}
 
-	if (!session->active) {
-		session->rotated_after_last_stop = true;
-	}
-
 	if (rotate_return) {
 		rotate_return->rotation_id = ongoing_rotation_chunk_id;
 	}