Move LTTng-UST buffer ownership from application to consumer

[lttng-tools.git] / src / bin / lttng-sessiond / consumer.c

/*
 * Copyright (C) 2012 - David Goulet <dgoulet@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.
 *
 * 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.
 */

#define _GNU_SOURCE
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include <common/common.h>
#include <common/defaults.h>
#include <common/uri.h>

#include "consumer.h"

/*
 * Receive a reply command status message from the consumer. Consumer socket
 * lock MUST be acquired before calling this function.
 *
 * Return 0 on success, -1 on recv error or a negative lttng error code which
 * was possibly returned by the consumer.
 */
int consumer_recv_status_reply(struct consumer_socket *sock)
{
	int ret;
	struct lttcomm_consumer_status_msg reply;

	assert(sock);

	ret = lttcomm_recv_unix_sock(sock->fd, &reply, sizeof(reply));
	if (ret <= 0) {
		if (ret == 0) {
			/* Orderly shutdown. Don't return 0 which means success. */
			ret = -1;
		}
		/* The above call will print a PERROR on error. */
		DBG("Fail to receive status reply on sock %d", sock->fd);
		goto end;
	}

	if (reply.ret_code == LTTNG_OK) {
		/* All good. */
		ret = 0;
	} else {
		ret = -reply.ret_code;
		DBG("Consumer ret code %d", ret);
	}

end:
	return ret;
}

/*
 * Once the ASK_CHANNEL command is sent to the consumer, the channel
 * information are sent back. This call receives that data and populates key
 * and stream_count.
 *
 * On success return 0 and both key and stream_count are set. On error, a
 * negative value is sent back and both parameters are untouched.
 */
int consumer_recv_status_channel(struct consumer_socket *sock,
		unsigned long *key, unsigned int *stream_count)
{
	int ret;
	struct lttcomm_consumer_status_channel reply;

	assert(sock);
	assert(stream_count);
	assert(key);

	ret = lttcomm_recv_unix_sock(sock->fd, &reply, sizeof(reply));
	if (ret <= 0) {
		if (ret == 0) {
			/* Orderly shutdown. Don't return 0 which means success. */
			ret = -1;
		}
		/* The above call will print a PERROR on error. */
		DBG("Fail to receive status reply on sock %d", sock->fd);
		goto end;
	}

	/* An error is possible so don't touch the key and stream_count. */
	if (reply.ret_code != LTTNG_OK) {
		ret = -1;
		goto end;
	}

	*key = reply.key;
	*stream_count = reply.stream_count;

end:
	return ret;
}

/*
 * Send destroy relayd command to consumer.
 *
 * On success return positive value. On error, negative value.
 */
int consumer_send_destroy_relayd(struct consumer_socket *sock,
		struct consumer_output *consumer)
{
	int ret;
	struct lttcomm_consumer_msg msg;

	assert(consumer);
	assert(sock);

	DBG2("Sending destroy relayd command to consumer sock %d", sock->fd);

	/* Bail out if consumer is disabled */
	if (!consumer->enabled) {
		ret = LTTNG_OK;
		DBG3("Consumer is disabled");
		goto error;
	}

	msg.cmd_type = LTTNG_CONSUMER_DESTROY_RELAYD;
	msg.u.destroy_relayd.net_seq_idx = consumer->net_seq_index;

	pthread_mutex_lock(sock->lock);
	ret = lttcomm_send_unix_sock(sock->fd, &msg, sizeof(msg));
	if (ret < 0) {
		/* Indicate that the consumer is probably closing at this point. */
		DBG("send consumer destroy relayd command");
		goto error_send;
	}

	/* Don't check the return value. The caller will do it. */
	ret = consumer_recv_status_reply(sock);

	DBG2("Consumer send destroy relayd command done");

error_send:
	pthread_mutex_unlock(sock->lock);
error:
	return ret;
}

/*
 * For each consumer socket in the consumer output object, send a destroy
 * relayd command.
 */
void consumer_output_send_destroy_relayd(struct consumer_output *consumer)
{
	struct lttng_ht_iter iter;
	struct consumer_socket *socket;

	assert(consumer);

	/* Destroy any relayd connection */
	if (consumer && consumer->type == CONSUMER_DST_NET) {
		rcu_read_lock();
		cds_lfht_for_each_entry(consumer->socks->ht, &iter.iter, socket,
				node.node) {
			int ret;

			/* Send destroy relayd command */
			ret = consumer_send_destroy_relayd(socket, consumer);
			if (ret < 0) {
				DBG("Unable to send destroy relayd command to consumer");
				/* Continue since we MUST delete everything at this point. */
			}
		}
		rcu_read_unlock();
	}
}

/*
 * From a consumer_data structure, allocate and add a consumer socket to the
 * consumer output.
 *
 * Return 0 on success, else negative value on error
 */
int consumer_create_socket(struct consumer_data *data,
		struct consumer_output *output)
{
	int ret = 0;
	struct consumer_socket *socket;

	assert(data);

	if (output == NULL || data->cmd_sock < 0) {
		/*
		 * Not an error. Possible there is simply not spawned consumer or it's
		 * disabled for the tracing session asking the socket.
		 */
		goto error;
	}

	rcu_read_lock();
	socket = consumer_find_socket(data->cmd_sock, output);
	rcu_read_unlock();
	if (socket == NULL) {
		socket = consumer_allocate_socket(data->cmd_sock);
		if (socket == NULL) {
			ret = -1;
			goto error;
		}

		socket->registered = 0;
		socket->lock = &data->lock;
		rcu_read_lock();
		consumer_add_socket(socket, output);
		rcu_read_unlock();
	}

	DBG3("Consumer socket created (fd: %d) and added to output",
			data->cmd_sock);

error:
	return ret;
}

/*
 * Find a consumer_socket in a consumer_output hashtable. Read side lock must
 * be acquired before calling this function and across use of the
 * returned consumer_socket.
 */
struct consumer_socket *consumer_find_socket(int key,
		struct consumer_output *consumer)
{
	struct lttng_ht_iter iter;
	struct lttng_ht_node_ulong *node;
	struct consumer_socket *socket = NULL;

	/* Negative keys are lookup failures */
	if (key < 0 || consumer == NULL) {
		return NULL;
	}

	lttng_ht_lookup(consumer->socks, (void *)((unsigned long) key),
			&iter);
	node = lttng_ht_iter_get_node_ulong(&iter);
	if (node != NULL) {
		socket = caa_container_of(node, struct consumer_socket, node);
	}

	return socket;
}

/*
 * Allocate a new consumer_socket and return the pointer.
 */
struct consumer_socket *consumer_allocate_socket(int fd)
{
	struct consumer_socket *socket = NULL;

	socket = zmalloc(sizeof(struct consumer_socket));
	if (socket == NULL) {
		PERROR("zmalloc consumer socket");
		goto error;
	}

	socket->fd = fd;
	lttng_ht_node_init_ulong(&socket->node, fd);

error:
	return socket;
}

/*
 * Add consumer socket to consumer output object. Read side lock must be
 * acquired before calling this function.
 */
void consumer_add_socket(struct consumer_socket *sock,
		struct consumer_output *consumer)
{
	assert(sock);
	assert(consumer);

	lttng_ht_add_unique_ulong(consumer->socks, &sock->node);
}

/*
 * Delte consumer socket to consumer output object. Read side lock must be
 * acquired before calling this function.
 */
void consumer_del_socket(struct consumer_socket *sock,
		struct consumer_output *consumer)
{
	int ret;
	struct lttng_ht_iter iter;

	assert(sock);
	assert(consumer);

	iter.iter.node = &sock->node.node;
	ret = lttng_ht_del(consumer->socks, &iter);
	assert(!ret);
}

/*
 * RCU destroy call function.
 */
static void destroy_socket_rcu(struct rcu_head *head)
{
	struct lttng_ht_node_ulong *node =
		caa_container_of(head, struct lttng_ht_node_ulong, head);
	struct consumer_socket *socket =
		caa_container_of(node, struct consumer_socket, node);

	free(socket);
}

/*
 * Destroy and free socket pointer in a call RCU. Read side lock must be
 * acquired before calling this function.
 */
void consumer_destroy_socket(struct consumer_socket *sock)
{
	assert(sock);

	/*
	 * We DO NOT close the file descriptor here since it is global to the
	 * session daemon and is closed only if the consumer dies or a custom
	 * consumer was registered,
	 */
	if (sock->registered) {
		DBG3("Consumer socket was registered. Closing fd %d", sock->fd);
		lttcomm_close_unix_sock(sock->fd);
	}

	call_rcu(&sock->node.head, destroy_socket_rcu);
}

/*
 * Allocate and assign data to a consumer_output object.
 *
 * Return pointer to structure.
 */
struct consumer_output *consumer_create_output(enum consumer_dst_type type)
{
	struct consumer_output *output = NULL;

	output = zmalloc(sizeof(struct consumer_output));
	if (output == NULL) {
		PERROR("zmalloc consumer_output");
		goto error;
	}

	/* By default, consumer output is enabled */
	output->enabled = 1;
	output->type = type;
	output->net_seq_index = -1;

	output->socks = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);

error:
	return output;
}

/*
 * Delete the consumer_output object from the list and free the ptr.
 */
void consumer_destroy_output(struct consumer_output *obj)
{
	if (obj == NULL) {
		return;
	}

	if (obj->socks) {
		struct lttng_ht_iter iter;
		struct consumer_socket *socket;

		rcu_read_lock();
		cds_lfht_for_each_entry(obj->socks->ht, &iter.iter, socket, node.node) {
			consumer_del_socket(socket, obj);
			consumer_destroy_socket(socket);
		}
		rcu_read_unlock();

		/* Finally destroy HT */
		lttng_ht_destroy(obj->socks);
	}

	free(obj);
}

/*
 * Copy consumer output and returned the newly allocated copy.
 */
struct consumer_output *consumer_copy_output(struct consumer_output *obj)
{
	struct lttng_ht *tmp_ht_ptr;
	struct lttng_ht_iter iter;
	struct consumer_socket *socket, *copy_sock;
	struct consumer_output *output;

	assert(obj);

	output = consumer_create_output(obj->type);
	if (output == NULL) {
		goto error;
	}
	/* Avoid losing the HT reference after the memcpy() */
	tmp_ht_ptr = output->socks;

	memcpy(output, obj, sizeof(struct consumer_output));

	/* Putting back the HT pointer and start copying socket(s). */
	output->socks = tmp_ht_ptr;

	rcu_read_lock();
	cds_lfht_for_each_entry(obj->socks->ht, &iter.iter, socket, node.node) {
		/* Create new socket object. */
		copy_sock = consumer_allocate_socket(socket->fd);
		if (copy_sock == NULL) {
			rcu_read_unlock();
			goto malloc_error;
		}

		copy_sock->registered = socket->registered;
		copy_sock->lock = socket->lock;
		consumer_add_socket(copy_sock, output);
	}
	rcu_read_unlock();

error:
	return output;

malloc_error:
	consumer_destroy_output(output);
	return NULL;
}

/*
 * Set network URI to the consumer output object.
 *
 * Return 0 on success. Return 1 if the URI were equal. Else, negative value on
 * error.
 */
int consumer_set_network_uri(struct consumer_output *obj,
		struct lttng_uri *uri)
{
	int ret;
	char tmp_path[PATH_MAX];
	char hostname[HOST_NAME_MAX];
	struct lttng_uri *dst_uri = NULL;

	/* Code flow error safety net. */
	assert(obj);
	assert(uri);

	switch (uri->stype) {
	case LTTNG_STREAM_CONTROL:
		dst_uri = &obj->dst.net.control;
		obj->dst.net.control_isset = 1;
		if (uri->port == 0) {
			/* Assign default port. */
			uri->port = DEFAULT_NETWORK_CONTROL_PORT;
		}
		DBG3("Consumer control URI set with port %d", uri->port);
		break;
	case LTTNG_STREAM_DATA:
		dst_uri = &obj->dst.net.data;
		obj->dst.net.data_isset = 1;
		if (uri->port == 0) {
			/* Assign default port. */
			uri->port = DEFAULT_NETWORK_DATA_PORT;
		}
		DBG3("Consumer data URI set with port %d", uri->port);
		break;
	default:
		ERR("Set network uri type unknown %d", uri->stype);
		goto error;
	}

	ret = uri_compare(dst_uri, uri);
	if (!ret) {
		/* Same URI, don't touch it and return success. */
		DBG3("URI network compare are the same");
		goto equal;
	}

	/* URIs were not equal, replacing it. */
	memset(dst_uri, 0, sizeof(struct lttng_uri));
	memcpy(dst_uri, uri, sizeof(struct lttng_uri));
	obj->type = CONSUMER_DST_NET;

	/* Handle subdir and add hostname in front. */
	if (dst_uri->stype == LTTNG_STREAM_CONTROL) {
		/* Get hostname to append it in the pathname */
		ret = gethostname(hostname, sizeof(hostname));
		if (ret < 0) {
			PERROR("gethostname. Fallback on default localhost");
			strncpy(hostname, "localhost", sizeof(hostname));
		}
		hostname[sizeof(hostname) - 1] = '\0';

		/* Setup consumer subdir if none present in the control URI */
		if (strlen(dst_uri->subdir) == 0) {
			ret = snprintf(tmp_path, sizeof(tmp_path), "%s/%s",
					hostname, obj->subdir);
		} else {
			ret = snprintf(tmp_path, sizeof(tmp_path), "%s/%s",
					hostname, dst_uri->subdir);
		}
		if (ret < 0) {
			PERROR("snprintf set consumer uri subdir");
			goto error;
		}

		strncpy(obj->subdir, tmp_path, sizeof(obj->subdir));
		DBG3("Consumer set network uri subdir path %s", tmp_path);
	}

	return 0;
equal:
	return 1;
error:
	return -1;
}

/*
 * Send file descriptor to consumer via sock.
 */
int consumer_send_fds(struct consumer_socket *sock, int *fds, size_t nb_fd)
{
	int ret;

	assert(fds);
	assert(sock);
	assert(nb_fd > 0);

	ret = lttcomm_send_fds_unix_sock(sock->fd, fds, nb_fd);
	if (ret < 0) {
		/* The above call will print a PERROR on error. */
		DBG("Error when sending consumer fds on sock %d", sock->fd);
		goto error;
	}

	ret = consumer_recv_status_reply(sock);

error:
	return ret;
}

/*
 * Consumer send communication message structure to consumer.
 */
int consumer_send_msg(struct consumer_socket *sock,
		struct lttcomm_consumer_msg *msg)
{
	int ret;

	assert(msg);
	assert(sock);
	assert(sock->fd >= 0);

	ret = lttcomm_send_unix_sock(sock->fd, msg,
			sizeof(struct lttcomm_consumer_msg));
	if (ret < 0) {
		/* The above call will print a PERROR on error. */
		DBG("Error when sending consumer channel on sock %d", sock->fd);
		goto error;
	}

	ret = consumer_recv_status_reply(sock);

error:
	return ret;
}

/*
 * Consumer send channel communication message structure to consumer.
 */
int consumer_send_channel(struct consumer_socket *sock,
		struct lttcomm_consumer_msg *msg)
{
	int ret;

	assert(msg);
	assert(sock);
	assert(sock->fd >= 0);

	ret = lttcomm_send_unix_sock(sock->fd, msg,
			sizeof(struct lttcomm_consumer_msg));
	if (ret < 0) {
		/* The above call will print a PERROR on error. */
		DBG("Error when sending consumer channel on sock %d", sock->fd);
		goto error;
	}

	ret = consumer_recv_status_reply(sock);

error:
	return ret;
}

/*
 * Populate the given consumer msg structure with the ask_channel command
 * information.
 */
void consumer_init_ask_channel_comm_msg(struct lttcomm_consumer_msg *msg,
		uint64_t subbuf_size,
		uint64_t num_subbuf,
		int overwrite,
		unsigned int switch_timer_interval,
		unsigned int read_timer_interval,
		int output,
		int type,
		uint64_t session_id,
		const char *pathname,
		const char *name,
		uid_t uid,
		gid_t gid,
		int relayd_id,
		unsigned long key,
		unsigned char *uuid)
{
	assert(msg);

	/* Zeroed structure */
	memset(msg, 0, sizeof(struct lttcomm_consumer_msg));

	msg->cmd_type = LTTNG_CONSUMER_ASK_CHANNEL_CREATION;
	msg->u.ask_channel.subbuf_size = subbuf_size;
	msg->u.ask_channel.num_subbuf = num_subbuf ;
	msg->u.ask_channel.overwrite = overwrite;
	msg->u.ask_channel.switch_timer_interval = switch_timer_interval;
	msg->u.ask_channel.read_timer_interval = read_timer_interval;
	msg->u.ask_channel.output = output;
	msg->u.ask_channel.type = type;
	msg->u.ask_channel.session_id = session_id;
	msg->u.ask_channel.uid = uid;
	msg->u.ask_channel.gid = gid;
	msg->u.ask_channel.relayd_id = relayd_id;
	msg->u.ask_channel.key = key;

	memcpy(msg->u.ask_channel.uuid, uuid, sizeof(msg->u.ask_channel.uuid));

	strncpy(msg->u.ask_channel.pathname, pathname,
			sizeof(msg->u.ask_channel.pathname));
	msg->u.ask_channel.pathname[sizeof(msg->u.ask_channel.pathname)-1] = '\0';

	strncpy(msg->u.ask_channel.name, name, sizeof(msg->u.ask_channel.name));
	msg->u.ask_channel.name[sizeof(msg->u.ask_channel.name) - 1] = '\0';
}

/*
 * Init channel communication message structure.
 */
void consumer_init_channel_comm_msg(struct lttcomm_consumer_msg *msg,
		enum lttng_consumer_command cmd,
		int channel_key,
		uint64_t session_id,
		const char *pathname,
		uid_t uid,
		gid_t gid,
		int relayd_id,
		const char *name,
		unsigned int nb_init_streams,
		enum lttng_event_output output,
		int type)
{
	assert(msg);

	/* Zeroed structure */
	memset(msg, 0, sizeof(struct lttcomm_consumer_msg));

	/* Send channel */
	msg->cmd_type = cmd;
	msg->u.channel.channel_key = channel_key;
	msg->u.channel.session_id = session_id;
	msg->u.channel.uid = uid;
	msg->u.channel.gid = gid;
	msg->u.channel.relayd_id = relayd_id;
	msg->u.channel.nb_init_streams = nb_init_streams;
	msg->u.channel.output = output;
	msg->u.channel.type = type;

	strncpy(msg->u.channel.pathname, pathname,
			sizeof(msg->u.channel.pathname));
	msg->u.channel.pathname[sizeof(msg->u.channel.pathname) - 1] = '\0';

	strncpy(msg->u.channel.name, name, sizeof(msg->u.channel.name));
	msg->u.channel.name[sizeof(msg->u.channel.name) - 1] = '\0';
}

/*
 * Init stream communication message structure.
 */
void consumer_init_stream_comm_msg(struct lttcomm_consumer_msg *msg,
		enum lttng_consumer_command cmd,
		int channel_key,
		int stream_key,
		int cpu)
{
	assert(msg);

	memset(msg, 0, sizeof(struct lttcomm_consumer_msg));

	msg->cmd_type = cmd;
	msg->u.stream.channel_key = channel_key;
	msg->u.stream.stream_key = stream_key;
	msg->u.stream.cpu = cpu;
}

/*
 * Send stream communication structure to the consumer.
 */
int consumer_send_stream(struct consumer_socket *sock,
		struct consumer_output *dst, struct lttcomm_consumer_msg *msg,
		int *fds, size_t nb_fd)
{
	int ret;

	assert(msg);
	assert(dst);
	assert(sock);
	assert(fds);

	/* Send on socket */
	ret = lttcomm_send_unix_sock(sock->fd, msg,
			sizeof(struct lttcomm_consumer_msg));
	if (ret < 0) {
		/* The above call will print a PERROR on error. */
		DBG("Error when sending consumer stream on sock %d", sock->fd);
		goto error;
	}

	ret = consumer_recv_status_reply(sock);
	if (ret < 0) {
		goto error;
	}

	ret = consumer_send_fds(sock, fds, nb_fd);
	if (ret < 0) {
		goto error;
	}

error:
	return ret;
}

/*
 * Send relayd socket to consumer associated with a session name.
 *
 * On success return positive value. On error, negative value.
 */
int consumer_send_relayd_socket(struct consumer_socket *consumer_sock,
		struct lttcomm_sock *sock, struct consumer_output *consumer,
		enum lttng_stream_type type, unsigned int session_id)
{
	int ret;
	struct lttcomm_consumer_msg msg;

	/* Code flow error. Safety net. */
	assert(sock);
	assert(consumer);
	assert(consumer_sock);

	/* Bail out if consumer is disabled */
	if (!consumer->enabled) {
		ret = LTTNG_OK;
		goto error;
	}

	msg.cmd_type = LTTNG_CONSUMER_ADD_RELAYD_SOCKET;
	/*
	 * Assign network consumer output index using the temporary consumer since
	 * this call should only be made from within a set_consumer_uri() function
	 * call in the session daemon.
	 */
	msg.u.relayd_sock.net_index = consumer->net_seq_index;
	msg.u.relayd_sock.type = type;
	msg.u.relayd_sock.session_id = session_id;
	memcpy(&msg.u.relayd_sock.sock, sock, sizeof(msg.u.relayd_sock.sock));

	DBG3("Sending relayd sock info to consumer on %d", consumer_sock->fd);
	ret = lttcomm_send_unix_sock(consumer_sock->fd, &msg, sizeof(msg));
	if (ret < 0) {
		/* The above call will print a PERROR on error. */
		DBG("Error when sending relayd sockets on sock %d", sock->fd);
		goto error;
	}

	ret = consumer_recv_status_reply(consumer_sock);
	if (ret < 0) {
		goto error;
	}

	DBG3("Sending relayd socket file descriptor to consumer");
	ret = consumer_send_fds(consumer_sock, &sock->fd, 1);
	if (ret < 0) {
		goto error;
	}

	DBG2("Consumer relayd socket sent");

error:
	return ret;
}

/*
 * Set consumer subdirectory using the session name and a generated datetime if
 * needed. This is appended to the current subdirectory.
 */
int consumer_set_subdir(struct consumer_output *consumer,
		const char *session_name)
{
	int ret = 0;
	unsigned int have_default_name = 0;
	char datetime[16], tmp_path[PATH_MAX];
	time_t rawtime;
	struct tm *timeinfo;

	assert(consumer);
	assert(session_name);

	memset(tmp_path, 0, sizeof(tmp_path));

	/* Flag if we have a default session. */
	if (strncmp(session_name, DEFAULT_SESSION_NAME "-",
				strlen(DEFAULT_SESSION_NAME) + 1) == 0) {
		have_default_name = 1;
	} else {
		/* Get date and time for session path */
		time(&rawtime);
		timeinfo = localtime(&rawtime);
		strftime(datetime, sizeof(datetime), "%Y%m%d-%H%M%S", timeinfo);
	}

	if (have_default_name) {
		ret = snprintf(tmp_path, sizeof(tmp_path),
				"%s/%s", consumer->subdir, session_name);
	} else {
		ret = snprintf(tmp_path, sizeof(tmp_path),
				"%s/%s-%s/", consumer->subdir, session_name, datetime);
	}
	if (ret < 0) {
		PERROR("snprintf session name date");
		goto error;
	}

	strncpy(consumer->subdir, tmp_path, sizeof(consumer->subdir));
	DBG2("Consumer subdir set to %s", consumer->subdir);

error:
	return ret;
}

/*
 * Ask the consumer if the data is ready to read (NOT pending) for the specific
 * session id.
 *
 * This function has a different behavior with the consumer i.e. that it waits
 * for a reply from the consumer if yes or no the data is pending.
 */
int consumer_is_data_pending(unsigned int id,
		struct consumer_output *consumer)
{
	int ret;
	int32_t ret_code = 0;  /* Default is that the data is NOT pending */
	struct consumer_socket *socket;
	struct lttng_ht_iter iter;
	struct lttcomm_consumer_msg msg;

	assert(consumer);

	msg.cmd_type = LTTNG_CONSUMER_DATA_PENDING;

	msg.u.data_pending.session_id = (uint64_t) id;

	DBG3("Consumer data pending for id %u", id);

	/* Send command for each consumer */
	rcu_read_lock();
	cds_lfht_for_each_entry(consumer->socks->ht, &iter.iter, socket,
			node.node) {
		/* Code flow error */
		assert(socket->fd >= 0);

		pthread_mutex_lock(socket->lock);

		ret = lttcomm_send_unix_sock(socket->fd, &msg, sizeof(msg));
		if (ret < 0) {
			/* The above call will print a PERROR on error. */
			DBG("Error on consumer is data pending on sock %d", socket->fd);
			pthread_mutex_unlock(socket->lock);
			goto error_unlock;
		}

		/*
		 * No need for a recv reply status because the answer to the command is
		 * the reply status message.
		 */

		ret = lttcomm_recv_unix_sock(socket->fd, &ret_code, sizeof(ret_code));
		if (ret <= 0) {
			if (ret == 0) {
				/* Orderly shutdown. Don't return 0 which means success. */
				ret = -1;
			}
			/* The above call will print a PERROR on error. */
			DBG("Error on recv consumer is data pending on sock %d", socket->fd);
			pthread_mutex_unlock(socket->lock);
			goto error_unlock;
		}

		pthread_mutex_unlock(socket->lock);

		if (ret_code == 1) {
			break;
		}
	}
	rcu_read_unlock();

	DBG("Consumer data is %s pending for session id %u",
			ret_code == 1 ? "" : "NOT", id);
	return ret_code;

error_unlock:
	rcu_read_unlock();
	return -1;
}