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

/*
 * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
 *
 * 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 <inttypes.h>
#include <string.h>
#include <unistd.h>

#include <common/common.h>
#include <common/defaults.h>
#include <common/sessiond-comm/sessiond-comm.h>

#include "channel.h"
#include "lttng-sessiond.h"
#include "kernel.h"
#include "ust-ctl.h"
#include "utils.h"
#include "ust-app.h"

/*
 * Return allocated channel attributes.
 */
struct lttng_channel *channel_new_default_attr(int dom,
		enum lttng_buffer_type type)
{
	struct lttng_channel *chan;

	chan = zmalloc(sizeof(struct lttng_channel));
	if (chan == NULL) {
		PERROR("zmalloc channel init");
		goto error_alloc;
	}

	if (snprintf(chan->name, sizeof(chan->name), "%s",
				DEFAULT_CHANNEL_NAME) < 0) {
		PERROR("snprintf default channel name");
		goto error;
	}

	/* Same for all domains. */
	chan->attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
	chan->attr.tracefile_size = DEFAULT_CHANNEL_TRACEFILE_SIZE;
	chan->attr.tracefile_count = DEFAULT_CHANNEL_TRACEFILE_COUNT;

	switch (dom) {
	case LTTNG_DOMAIN_KERNEL:
		assert(type == LTTNG_BUFFER_GLOBAL);
		chan->attr.subbuf_size =
			default_get_kernel_channel_subbuf_size();
		chan->attr.num_subbuf = DEFAULT_KERNEL_CHANNEL_SUBBUF_NUM;
		chan->attr.output = DEFAULT_KERNEL_CHANNEL_OUTPUT;
		chan->attr.switch_timer_interval = DEFAULT_KERNEL_CHANNEL_SWITCH_TIMER;
		chan->attr.read_timer_interval = DEFAULT_KERNEL_CHANNEL_READ_TIMER;
		chan->attr.live_timer_interval = DEFAULT_KERNEL_CHANNEL_LIVE_TIMER;
		break;
	case LTTNG_DOMAIN_UST:
		switch (type) {
		case LTTNG_BUFFER_PER_UID:
			chan->attr.subbuf_size = default_get_ust_uid_channel_subbuf_size();
			chan->attr.num_subbuf = DEFAULT_UST_UID_CHANNEL_SUBBUF_NUM;
			chan->attr.output = DEFAULT_UST_UID_CHANNEL_OUTPUT;
			chan->attr.switch_timer_interval =
				DEFAULT_UST_UID_CHANNEL_SWITCH_TIMER;
			chan->attr.read_timer_interval =
				DEFAULT_UST_UID_CHANNEL_READ_TIMER;
			chan->attr.live_timer_interval =
				DEFAULT_UST_UID_CHANNEL_LIVE_TIMER;
			break;
		case LTTNG_BUFFER_PER_PID:
		default:
			chan->attr.subbuf_size = default_get_ust_pid_channel_subbuf_size();
			chan->attr.num_subbuf = DEFAULT_UST_PID_CHANNEL_SUBBUF_NUM;
			chan->attr.output = DEFAULT_UST_PID_CHANNEL_OUTPUT;
			chan->attr.switch_timer_interval =
				DEFAULT_UST_PID_CHANNEL_SWITCH_TIMER;
			chan->attr.read_timer_interval =
				DEFAULT_UST_PID_CHANNEL_READ_TIMER;
			chan->attr.live_timer_interval =
				DEFAULT_UST_UID_CHANNEL_LIVE_TIMER;
			break;
		}
		break;
	default:
		goto error;	/* Not implemented */
	}

	return chan;

error:
	free(chan);
error_alloc:
	return NULL;
}

/*
 * Disable kernel channel of the kernel session.
 */
int channel_kernel_disable(struct ltt_kernel_session *ksession,
		char *channel_name)
{
	int ret;
	struct ltt_kernel_channel *kchan;

	assert(ksession);
	assert(channel_name);

	kchan = trace_kernel_get_channel_by_name(channel_name, ksession);
	if (kchan == NULL) {
		ret = LTTNG_ERR_KERN_CHAN_NOT_FOUND;
		goto error;
	}

	/* Only if channel is enabled disable it. */
	if (kchan->enabled == 1) {
		ret = kernel_disable_channel(kchan);
		if (ret < 0 && ret != -EEXIST) {
			ret = LTTNG_ERR_KERN_CHAN_DISABLE_FAIL;
			goto error;
		}
	}

	ret = LTTNG_OK;

error:
	return ret;
}

/*
 * Enable kernel channel of the kernel session.
 */
int channel_kernel_enable(struct ltt_kernel_session *ksession,
		struct ltt_kernel_channel *kchan)
{
	int ret;

	assert(ksession);
	assert(kchan);

	if (kchan->enabled == 0) {
		ret = kernel_enable_channel(kchan);
		if (ret < 0) {
			ret = LTTNG_ERR_KERN_CHAN_ENABLE_FAIL;
			goto error;
		}
	} else {
		ret = LTTNG_ERR_KERN_CHAN_EXIST;
		goto error;
	}

	ret = LTTNG_OK;

error:
	return ret;
}

/*
 * Create kernel channel of the kernel session and notify kernel thread.
 */
int channel_kernel_create(struct ltt_kernel_session *ksession,
		struct lttng_channel *attr, int kernel_pipe)
{
	int ret;
	struct lttng_channel *defattr = NULL;

	assert(ksession);

	/* Creating channel attributes if needed */
	if (attr == NULL) {
		defattr = channel_new_default_attr(LTTNG_DOMAIN_KERNEL,
				LTTNG_BUFFER_GLOBAL);
		if (defattr == NULL) {
			ret = LTTNG_ERR_FATAL;
			goto error;
		}
		attr = defattr;
	}

	if (ksession->snapshot_mode) {
		/* Force channel attribute for snapshot mode. */
		attr->attr.overwrite = 1;
		attr->attr.output = LTTNG_EVENT_MMAP;
	}

	/* Channel not found, creating it */
	ret = kernel_create_channel(ksession, attr);
	if (ret < 0) {
		ret = LTTNG_ERR_KERN_CHAN_FAIL;
		goto error;
	}

	/* Notify kernel thread that there is a new channel */
	ret = notify_thread_pipe(kernel_pipe);
	if (ret < 0) {
		ret = LTTNG_ERR_FATAL;
		goto error;
	}

	ret = LTTNG_OK;
error:
	free(defattr);
	return ret;
}

/*
 * Enable UST channel for session and domain.
 */
int channel_ust_enable(struct ltt_ust_session *usess,
		struct ltt_ust_channel *uchan)
{
	int ret = LTTNG_OK;

	assert(usess);
	assert(uchan);

	/* If already enabled, everything is OK */
	if (uchan->enabled) {
		DBG3("Channel %s already enabled. Skipping", uchan->name);
		ret = LTTNG_ERR_UST_CHAN_EXIST;
		goto end;
	}

	DBG2("Channel %s being enabled in UST domain", uchan->name);

	/*
	 * Enable channel for UST global domain on all applications. Ignore return
	 * value here since whatever error we got, it means that the channel was
	 * not created on one or many registered applications and we can not report
	 * this to the user yet. However, at this stage, the channel was
	 * successfully created on the session daemon side so the enable-channel
	 * command is a success.
	 */
	(void) ust_app_enable_channel_glb(usess, uchan);

	uchan->enabled = 1;
	DBG2("Channel %s enabled successfully", uchan->name);

end:
	return ret;
}

/*
 * Create UST channel for session and domain.
 */
int channel_ust_create(struct ltt_ust_session *usess,
		struct lttng_channel *attr, enum lttng_buffer_type type)
{
	int ret = LTTNG_OK;
	struct ltt_ust_channel *uchan = NULL;
	struct lttng_channel *defattr = NULL;

	assert(usess);

	/* Creating channel attributes if needed */
	if (attr == NULL) {
		defattr = channel_new_default_attr(LTTNG_DOMAIN_UST, type);
		if (defattr == NULL) {
			ret = LTTNG_ERR_FATAL;
			goto error;
		}
		attr = defattr;
	}

	if (usess->snapshot_mode) {
		/* Force channel attribute for snapshot mode. */
		attr->attr.overwrite = 1;
		attr->attr.output = LTTNG_EVENT_MMAP;
	}

	/*
	 * Validate UST buffer size and number of buffers: must both be power of 2
	 * and nonzero. We validate right here for UST, because applications will
	 * not report the error to the user (unlike kernel tracing).
	 */
	if (!attr->attr.subbuf_size ||
			(attr->attr.subbuf_size & (attr->attr.subbuf_size - 1))) {
		ret = LTTNG_ERR_INVALID;
		goto error;
	}

	/*
	 * Invalid subbuffer size if it's lower then the page size.
	 */
	if (attr->attr.subbuf_size < page_size) {
		ret = LTTNG_ERR_INVALID;
		goto error;
	}

	if (!attr->attr.num_subbuf ||
			(attr->attr.num_subbuf & (attr->attr.num_subbuf - 1))) {
		ret = LTTNG_ERR_INVALID;
		goto error;
	}

	if (attr->attr.output != LTTNG_EVENT_MMAP) {
		ret = LTTNG_ERR_NOT_SUPPORTED;
		goto error;
	}

	/*
	 * The tracefile_size should not be < to the subbuf_size, otherwise
	 * we won't be able to write the packets on disk
	 */
	if ((attr->attr.tracefile_size > 0) &&
			(attr->attr.tracefile_size < attr->attr.subbuf_size)) {
		ret = LTTNG_ERR_INVALID;
		goto error;
	}

	/* Validate buffer type. */
	switch (type) {
	case LTTNG_BUFFER_PER_PID:
		break;
	case LTTNG_BUFFER_PER_UID:
		break;
	default:
		ret = LTTNG_ERR_BUFFER_NOT_SUPPORTED;
		goto error;
	}

	/* Create UST channel */
	uchan = trace_ust_create_channel(attr);
	if (uchan == NULL) {
		ret = LTTNG_ERR_FATAL;
		goto error;
	}
	uchan->enabled = 1;
	if (trace_ust_is_max_id(usess->used_channel_id)) {
		ret = LTTNG_ERR_UST_CHAN_FAIL;
		goto error;
	}
	uchan->id = trace_ust_get_next_chan_id(usess);

	DBG2("Channel %s is being created for UST with buffer %d and id %" PRIu64,
			uchan->name, type, uchan->id);

	/* Flag session buffer type. */
	if (!usess->buffer_type_changed) {
		usess->buffer_type = type;
		usess->buffer_type_changed = 1;
	} else if (usess->buffer_type != type) {
		/* Buffer type was already set. Refuse to create channel. */
		ret = LTTNG_ERR_BUFFER_TYPE_MISMATCH;
		goto error_free_chan;
	}

	/* Enable channel for global domain */
	ret = ust_app_create_channel_glb(usess, uchan);
	if (ret < 0 && ret != -LTTNG_UST_ERR_EXIST) {
		ret = LTTNG_ERR_UST_CHAN_FAIL;
		goto error_free_chan;
	}

	/* Adding the channel to the channel hash table. */
	rcu_read_lock();
	if (strncmp(uchan->name, DEFAULT_METADATA_NAME,
				sizeof(uchan->name))) {
		lttng_ht_add_unique_str(usess->domain_global.channels, &uchan->node);
	} else {
		/*
		 * Copy channel attribute to session if this is metadata so if NO
		 * application exists we can access that data in the shadow copy during
		 * the global update of newly registered application.
		 */
		memcpy(&usess->metadata_attr, &uchan->attr,
				sizeof(usess->metadata_attr));
	}
	rcu_read_unlock();

	DBG2("Channel %s created successfully", uchan->name);

	free(defattr);
	return LTTNG_OK;

error_free_chan:
	/*
	 * No need to remove the channel from the hash table because at this point
	 * it was not added hence the direct call and no call_rcu().
	 */
	trace_ust_destroy_channel(uchan);
error:
	free(defattr);
	return ret;
}

/*
 * Disable UST channel for session and domain.
 */
int channel_ust_disable(struct ltt_ust_session *usess,
		struct ltt_ust_channel *uchan)
{
	int ret = LTTNG_OK;

	assert(usess);
	assert(uchan);

	/* Already disabled */
	if (uchan->enabled == 0) {
		DBG2("Channel UST %s already disabled", uchan->name);
		goto end;
	}

	DBG2("Channel %s being disabled in UST global domain", uchan->name);
	/* Disable channel for global domain */
	ret = ust_app_disable_channel_glb(usess, uchan);
	if (ret < 0 && ret != -LTTNG_UST_ERR_EXIST) {
		ret = LTTNG_ERR_UST_CHAN_DISABLE_FAIL;
		goto error;
	}

	uchan->enabled = 0;

	DBG2("Channel %s disabled successfully", uchan->name);

	return LTTNG_OK;

end:
error:
	return ret;
}
Commit	Line	Data
	1	/*
	2	* Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License, version 2 only,
	6	* as published by the Free Software Foundation.
	7	*
	8	* This program is distributed in the hope that it will be useful,
	9	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	10	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	11	* GNU General Public License for more details.
	12	*
	13	* You should have received a copy of the GNU General Public License along
	14	* with this program; if not, write to the Free Software Foundation, Inc.,
	15	* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
	16	*/
	17
	18	#define _GNU_SOURCE
	19	#include <inttypes.h>
	20	#include <string.h>
	21	#include <unistd.h>
	22
	23	#include <common/common.h>
	24	#include <common/defaults.h>
	25	#include <common/sessiond-comm/sessiond-comm.h>
	26
	27	#include "channel.h"
	28	#include "lttng-sessiond.h"
	29	#include "kernel.h"
	30	#include "ust-ctl.h"
	31	#include "utils.h"
	32	#include "ust-app.h"
	33
	34	/*
	35	* Return allocated channel attributes.
	36	*/
	37	struct lttng_channel *channel_new_default_attr(int dom,
	38	enum lttng_buffer_type type)
	39	{
	40	struct lttng_channel *chan;
	41
	42	chan = zmalloc(sizeof(struct lttng_channel));
	43	if (chan == NULL) {
	44	PERROR("zmalloc channel init");
	45	goto error_alloc;
	46	}
	47
	48	if (snprintf(chan->name, sizeof(chan->name), "%s",
	49	DEFAULT_CHANNEL_NAME) < 0) {
	50	PERROR("snprintf default channel name");
	51	goto error;
	52	}
	53
	54	/* Same for all domains. */
	55	chan->attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
	56	chan->attr.tracefile_size = DEFAULT_CHANNEL_TRACEFILE_SIZE;
	57	chan->attr.tracefile_count = DEFAULT_CHANNEL_TRACEFILE_COUNT;
	58
	59	switch (dom) {
	60	case LTTNG_DOMAIN_KERNEL:
	61	assert(type == LTTNG_BUFFER_GLOBAL);
	62	chan->attr.subbuf_size =
	63	default_get_kernel_channel_subbuf_size();
	64	chan->attr.num_subbuf = DEFAULT_KERNEL_CHANNEL_SUBBUF_NUM;
	65	chan->attr.output = DEFAULT_KERNEL_CHANNEL_OUTPUT;
	66	chan->attr.switch_timer_interval = DEFAULT_KERNEL_CHANNEL_SWITCH_TIMER;
	67	chan->attr.read_timer_interval = DEFAULT_KERNEL_CHANNEL_READ_TIMER;
	68	chan->attr.live_timer_interval = DEFAULT_KERNEL_CHANNEL_LIVE_TIMER;
	69	break;
	70	case LTTNG_DOMAIN_UST:
	71	switch (type) {
	72	case LTTNG_BUFFER_PER_UID:
	73	chan->attr.subbuf_size = default_get_ust_uid_channel_subbuf_size();
	74	chan->attr.num_subbuf = DEFAULT_UST_UID_CHANNEL_SUBBUF_NUM;
	75	chan->attr.output = DEFAULT_UST_UID_CHANNEL_OUTPUT;
	76	chan->attr.switch_timer_interval =
	77	DEFAULT_UST_UID_CHANNEL_SWITCH_TIMER;
	78	chan->attr.read_timer_interval =
	79	DEFAULT_UST_UID_CHANNEL_READ_TIMER;
	80	chan->attr.live_timer_interval =
	81	DEFAULT_UST_UID_CHANNEL_LIVE_TIMER;
	82	break;
	83	case LTTNG_BUFFER_PER_PID:
	84	default:
	85	chan->attr.subbuf_size = default_get_ust_pid_channel_subbuf_size();
	86	chan->attr.num_subbuf = DEFAULT_UST_PID_CHANNEL_SUBBUF_NUM;
	87	chan->attr.output = DEFAULT_UST_PID_CHANNEL_OUTPUT;
	88	chan->attr.switch_timer_interval =
	89	DEFAULT_UST_PID_CHANNEL_SWITCH_TIMER;
	90	chan->attr.read_timer_interval =
	91	DEFAULT_UST_PID_CHANNEL_READ_TIMER;
	92	chan->attr.live_timer_interval =
	93	DEFAULT_UST_UID_CHANNEL_LIVE_TIMER;
	94	break;
	95	}
	96	break;
	97	default:
	98	goto error; /* Not implemented */
	99	}
	100
	101	return chan;
	102
	103	error:
	104	free(chan);
	105	error_alloc:
	106	return NULL;
	107	}
	108
	109	/*
	110	* Disable kernel channel of the kernel session.
	111	*/
	112	int channel_kernel_disable(struct ltt_kernel_session *ksession,
	113	char *channel_name)
	114	{
	115	int ret;
	116	struct ltt_kernel_channel *kchan;
	117
	118	assert(ksession);
	119	assert(channel_name);
	120
	121	kchan = trace_kernel_get_channel_by_name(channel_name, ksession);
	122	if (kchan == NULL) {
	123	ret = LTTNG_ERR_KERN_CHAN_NOT_FOUND;
	124	goto error;
	125	}
	126
	127	/* Only if channel is enabled disable it. */
	128	if (kchan->enabled == 1) {
	129	ret = kernel_disable_channel(kchan);
	130	if (ret < 0 && ret != -EEXIST) {
	131	ret = LTTNG_ERR_KERN_CHAN_DISABLE_FAIL;
	132	goto error;
	133	}
	134	}
	135
	136	ret = LTTNG_OK;
	137
	138	error:
	139	return ret;
	140	}
	141
	142	/*
	143	* Enable kernel channel of the kernel session.
	144	*/
	145	int channel_kernel_enable(struct ltt_kernel_session *ksession,
	146	struct ltt_kernel_channel *kchan)
	147	{
	148	int ret;
	149
	150	assert(ksession);
	151	assert(kchan);
	152
	153	if (kchan->enabled == 0) {
	154	ret = kernel_enable_channel(kchan);
	155	if (ret < 0) {
	156	ret = LTTNG_ERR_KERN_CHAN_ENABLE_FAIL;
	157	goto error;
	158	}
	159	} else {
	160	ret = LTTNG_ERR_KERN_CHAN_EXIST;
	161	goto error;
	162	}
	163
	164	ret = LTTNG_OK;
	165
	166	error:
	167	return ret;
	168	}
	169
	170	/*
	171	* Create kernel channel of the kernel session and notify kernel thread.
	172	*/
	173	int channel_kernel_create(struct ltt_kernel_session *ksession,
	174	struct lttng_channel *attr, int kernel_pipe)
	175	{
	176	int ret;
	177	struct lttng_channel *defattr = NULL;
	178
	179	assert(ksession);
	180
	181	/* Creating channel attributes if needed */
	182	if (attr == NULL) {
	183	defattr = channel_new_default_attr(LTTNG_DOMAIN_KERNEL,
	184	LTTNG_BUFFER_GLOBAL);
	185	if (defattr == NULL) {
	186	ret = LTTNG_ERR_FATAL;
	187	goto error;
	188	}
	189	attr = defattr;
	190	}
	191
	192	if (ksession->snapshot_mode) {
	193	/* Force channel attribute for snapshot mode. */
	194	attr->attr.overwrite = 1;
	195	attr->attr.output = LTTNG_EVENT_MMAP;
	196	}
	197
	198	/* Channel not found, creating it */
	199	ret = kernel_create_channel(ksession, attr);
	200	if (ret < 0) {
	201	ret = LTTNG_ERR_KERN_CHAN_FAIL;
	202	goto error;
	203	}
	204
	205	/* Notify kernel thread that there is a new channel */
	206	ret = notify_thread_pipe(kernel_pipe);
	207	if (ret < 0) {
	208	ret = LTTNG_ERR_FATAL;
	209	goto error;
	210	}
	211
	212	ret = LTTNG_OK;
	213	error:
	214	free(defattr);
	215	return ret;
	216	}
	217
	218	/*
	219	* Enable UST channel for session and domain.
	220	*/
	221	int channel_ust_enable(struct ltt_ust_session *usess,
	222	struct ltt_ust_channel *uchan)
	223	{
	224	int ret = LTTNG_OK;
	225
	226	assert(usess);
	227	assert(uchan);
	228
	229	/* If already enabled, everything is OK */
	230	if (uchan->enabled) {
	231	DBG3("Channel %s already enabled. Skipping", uchan->name);
	232	ret = LTTNG_ERR_UST_CHAN_EXIST;
	233	goto end;
	234	}
	235
	236	DBG2("Channel %s being enabled in UST domain", uchan->name);
	237
	238	/*
	239	* Enable channel for UST global domain on all applications. Ignore return
	240	* value here since whatever error we got, it means that the channel was
	241	* not created on one or many registered applications and we can not report
	242	* this to the user yet. However, at this stage, the channel was
	243	* successfully created on the session daemon side so the enable-channel
	244	* command is a success.
	245	*/
	246	(void) ust_app_enable_channel_glb(usess, uchan);
	247
	248	uchan->enabled = 1;
	249	DBG2("Channel %s enabled successfully", uchan->name);
	250
	251	end:
	252	return ret;
	253	}
	254
	255	/*
	256	* Create UST channel for session and domain.
	257	*/
	258	int channel_ust_create(struct ltt_ust_session *usess,
	259	struct lttng_channel *attr, enum lttng_buffer_type type)
	260	{
	261	int ret = LTTNG_OK;
	262	struct ltt_ust_channel *uchan = NULL;
	263	struct lttng_channel *defattr = NULL;
	264
	265	assert(usess);
	266
	267	/* Creating channel attributes if needed */
	268	if (attr == NULL) {
	269	defattr = channel_new_default_attr(LTTNG_DOMAIN_UST, type);
	270	if (defattr == NULL) {
	271	ret = LTTNG_ERR_FATAL;
	272	goto error;
	273	}
	274	attr = defattr;
	275	}
	276
	277	if (usess->snapshot_mode) {
	278	/* Force channel attribute for snapshot mode. */
	279	attr->attr.overwrite = 1;
	280	attr->attr.output = LTTNG_EVENT_MMAP;
	281	}
	282
	283	/*
	284	* Validate UST buffer size and number of buffers: must both be power of 2
	285	* and nonzero. We validate right here for UST, because applications will
	286	* not report the error to the user (unlike kernel tracing).
	287	*/
	288	if (!attr->attr.subbuf_size \|\|
	289	(attr->attr.subbuf_size & (attr->attr.subbuf_size - 1))) {
	290	ret = LTTNG_ERR_INVALID;
	291	goto error;
	292	}
	293
	294	/*
	295	* Invalid subbuffer size if it's lower then the page size.
	296	*/
	297	if (attr->attr.subbuf_size < page_size) {
	298	ret = LTTNG_ERR_INVALID;
	299	goto error;
	300	}
	301
	302	if (!attr->attr.num_subbuf \|\|
	303	(attr->attr.num_subbuf & (attr->attr.num_subbuf - 1))) {
	304	ret = LTTNG_ERR_INVALID;
	305	goto error;
	306	}
	307
	308	if (attr->attr.output != LTTNG_EVENT_MMAP) {
	309	ret = LTTNG_ERR_NOT_SUPPORTED;
	310	goto error;
	311	}
	312
	313	/*
	314	* The tracefile_size should not be < to the subbuf_size, otherwise
	315	* we won't be able to write the packets on disk
	316	*/
	317	if ((attr->attr.tracefile_size > 0) &&
	318	(attr->attr.tracefile_size < attr->attr.subbuf_size)) {
	319	ret = LTTNG_ERR_INVALID;
	320	goto error;
	321	}
	322
	323	/* Validate buffer type. */
	324	switch (type) {
	325	case LTTNG_BUFFER_PER_PID:
	326	break;
	327	case LTTNG_BUFFER_PER_UID:
	328	break;
	329	default:
	330	ret = LTTNG_ERR_BUFFER_NOT_SUPPORTED;
	331	goto error;
	332	}
	333
	334	/* Create UST channel */
	335	uchan = trace_ust_create_channel(attr);
	336	if (uchan == NULL) {
	337	ret = LTTNG_ERR_FATAL;
	338	goto error;
	339	}
	340	uchan->enabled = 1;
	341	if (trace_ust_is_max_id(usess->used_channel_id)) {
	342	ret = LTTNG_ERR_UST_CHAN_FAIL;
	343	goto error;
	344	}
	345	uchan->id = trace_ust_get_next_chan_id(usess);
	346
	347	DBG2("Channel %s is being created for UST with buffer %d and id %" PRIu64,
	348	uchan->name, type, uchan->id);
	349
	350	/* Flag session buffer type. */
	351	if (!usess->buffer_type_changed) {
	352	usess->buffer_type = type;
	353	usess->buffer_type_changed = 1;
	354	} else if (usess->buffer_type != type) {
	355	/* Buffer type was already set. Refuse to create channel. */
	356	ret = LTTNG_ERR_BUFFER_TYPE_MISMATCH;
	357	goto error_free_chan;
	358	}
	359
	360	/* Enable channel for global domain */
	361	ret = ust_app_create_channel_glb(usess, uchan);
	362	if (ret < 0 && ret != -LTTNG_UST_ERR_EXIST) {
	363	ret = LTTNG_ERR_UST_CHAN_FAIL;
	364	goto error_free_chan;
	365	}
	366
	367	/* Adding the channel to the channel hash table. */
	368	rcu_read_lock();
	369	if (strncmp(uchan->name, DEFAULT_METADATA_NAME,
	370	sizeof(uchan->name))) {
	371	lttng_ht_add_unique_str(usess->domain_global.channels, &uchan->node);
	372	} else {
	373	/*
	374	* Copy channel attribute to session if this is metadata so if NO
	375	* application exists we can access that data in the shadow copy during
	376	* the global update of newly registered application.
	377	*/
	378	memcpy(&usess->metadata_attr, &uchan->attr,
	379	sizeof(usess->metadata_attr));
	380	}
	381	rcu_read_unlock();
	382
	383	DBG2("Channel %s created successfully", uchan->name);
	384
	385	free(defattr);
	386	return LTTNG_OK;
	387
	388	error_free_chan:
	389	/*
	390	* No need to remove the channel from the hash table because at this point
	391	* it was not added hence the direct call and no call_rcu().
	392	*/
	393	trace_ust_destroy_channel(uchan);
	394	error:
	395	free(defattr);
	396	return ret;
	397	}
	398
	399	/*
	400	* Disable UST channel for session and domain.
	401	*/
	402	int channel_ust_disable(struct ltt_ust_session *usess,
	403	struct ltt_ust_channel *uchan)
	404	{
	405	int ret = LTTNG_OK;
	406
	407	assert(usess);
	408	assert(uchan);
	409
	410	/* Already disabled */
	411	if (uchan->enabled == 0) {
	412	DBG2("Channel UST %s already disabled", uchan->name);
	413	goto end;
	414	}
	415
	416	DBG2("Channel %s being disabled in UST global domain", uchan->name);
	417	/* Disable channel for global domain */
	418	ret = ust_app_disable_channel_glb(usess, uchan);
	419	if (ret < 0 && ret != -LTTNG_UST_ERR_EXIST) {
	420	ret = LTTNG_ERR_UST_CHAN_DISABLE_FAIL;
	421	goto error;
	422	}
	423
	424	uchan->enabled = 0;
	425
	426	DBG2("Channel %s disabled successfully", uchan->name);
	427
	428	return LTTNG_OK;
	429
	430	end:
	431	error:
	432	return ret;
	433	}