libust: New transport mutex v2

[ust.git] / libust / tracer.c

/*
 * tracer.c
 *
 * (C) Copyright	2005-2008 -
 * 		Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca)
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
 *
 * Inspired from LTT :
 *  Karim Yaghmour (karim@opersys.com)
 *  Tom Zanussi (zanussi@us.ibm.com)
 *  Bob Wisniewski (bob@watson.ibm.com)
 * And from K42 :
 *  Bob Wisniewski (bob@watson.ibm.com)
 *
 * Changelog:
 *  22/09/06, Move to the marker/probes mechanism.
 *  19/10/05, Complete lockless mechanism.
 *  27/05/05, Modular redesign and rewrite.
 */

#include <urcu-bp.h>
#include <urcu/rculist.h>

#include <ust/clock.h>

#include "tracercore.h"
#include "tracer.h"
#include "usterr.h"

//ust// static void async_wakeup(unsigned long data);
//ust// 
//ust// static DEFINE_TIMER(ltt_async_wakeup_timer, async_wakeup, 0, 0);

/* Default callbacks for modules */
notrace int ltt_filter_control_default(enum ltt_filter_control_msg msg,
		struct ust_trace *trace)
{
	return 0;
}

int ltt_statedump_default(struct ust_trace *trace)
{
	return 0;
}

/* Callbacks for registered modules */

int (*ltt_filter_control_functor)
	(enum ltt_filter_control_msg msg, struct ust_trace *trace) =
					ltt_filter_control_default;
struct module *ltt_filter_control_owner;

/* These function pointers are protected by a trace activation check */
struct module *ltt_run_filter_owner;
int (*ltt_statedump_functor)(struct ust_trace *trace) =
					ltt_statedump_default;
struct module *ltt_statedump_owner;

struct chan_info_struct chan_infos[] = {
	[LTT_CHANNEL_METADATA] = {
		LTT_METADATA_CHANNEL,
		LTT_DEFAULT_SUBBUF_SIZE_LOW,
		LTT_DEFAULT_N_SUBBUFS_LOW,
	},
	[LTT_CHANNEL_UST] = {
		LTT_UST_CHANNEL,
		LTT_DEFAULT_SUBBUF_SIZE_HIGH,
		LTT_DEFAULT_N_SUBBUFS_HIGH,
	},
};

static enum ltt_channels get_channel_type_from_name(const char *name)
{
	int i;

	if (!name)
		return LTT_CHANNEL_UST;

	for (i = 0; i < ARRAY_SIZE(chan_infos); i++)
		if (chan_infos[i].name && !strcmp(name, chan_infos[i].name))
			return (enum ltt_channels)i;

	return LTT_CHANNEL_UST;
}

/**
 * ltt_module_register - LTT module registration
 * @name: module type
 * @function: callback to register
 * @owner: module which owns the callback
 *
 * The module calling this registration function must ensure that no
 * trap-inducing code will be executed by "function". E.g. vmalloc_sync_all()
 * must be called between a vmalloc and the moment the memory is made visible to
 * "function". This registration acts as a vmalloc_sync_all. Therefore, only if
 * the module allocates virtual memory after its registration must it
 * synchronize the TLBs.
 */
//ust// int ltt_module_register(enum ltt_module_function name, void *function,
//ust// 		struct module *owner)
//ust// {
//ust// 	int ret = 0;
//ust// 
//ust// 	/*
//ust// 	 * Make sure no page fault can be triggered by the module about to be
//ust// 	 * registered. We deal with this here so we don't have to call
//ust// 	 * vmalloc_sync_all() in each module's init.
//ust// 	 */
//ust// 	vmalloc_sync_all();
//ust// 
//ust// 	switch (name) {
//ust// 	case LTT_FUNCTION_RUN_FILTER:
//ust// 		if (ltt_run_filter_owner != NULL) {
//ust// 			ret = -EEXIST;
//ust// 			goto end;
//ust// 		}
//ust// 		ltt_filter_register((ltt_run_filter_functor)function);
//ust// 		ltt_run_filter_owner = owner;
//ust// 		break;
//ust// 	case LTT_FUNCTION_FILTER_CONTROL:
//ust// 		if (ltt_filter_control_owner != NULL) {
//ust// 			ret = -EEXIST;
//ust// 			goto end;
//ust// 		}
//ust// 		ltt_filter_control_functor =
//ust// 			(int (*)(enum ltt_filter_control_msg,
//ust// 			struct ust_trace *))function;
//ust// 		ltt_filter_control_owner = owner;
//ust// 		break;
//ust// 	case LTT_FUNCTION_STATEDUMP:
//ust// 		if (ltt_statedump_owner != NULL) {
//ust// 			ret = -EEXIST;
//ust// 			goto end;
//ust// 		}
//ust// 		ltt_statedump_functor =
//ust// 			(int (*)(struct ust_trace *))function;
//ust// 		ltt_statedump_owner = owner;
//ust// 		break;
//ust// 	}
//ust// 
//ust// end:
//ust// 
//ust// 	return ret;
//ust// }

/**
 * ltt_module_unregister - LTT module unregistration
 * @name: module type
 */
//ust// void ltt_module_unregister(enum ltt_module_function name)
//ust// {
//ust// 	switch (name) {
//ust// 	case LTT_FUNCTION_RUN_FILTER:
//ust// 		ltt_filter_unregister();
//ust// 		ltt_run_filter_owner = NULL;
//ust// 		/* Wait for preempt sections to finish */
//ust// 		synchronize_sched();
//ust// 		break;
//ust// 	case LTT_FUNCTION_FILTER_CONTROL:
//ust// 		ltt_filter_control_functor = ltt_filter_control_default;
//ust// 		ltt_filter_control_owner = NULL;
//ust// 		break;
//ust// 	case LTT_FUNCTION_STATEDUMP:
//ust// 		ltt_statedump_functor = ltt_statedump_default;
//ust// 		ltt_statedump_owner = NULL;
//ust// 		break;
//ust// 	}
//ust// 
//ust// }

static CDS_LIST_HEAD(ltt_transport_list);
/* transport mutex, nests inside traces mutex (ltt_lock_traces) */
static DEFINE_MUTEX(ltt_transport_mutex);
/**
 * ltt_transport_register - LTT transport registration
 * @transport: transport structure
 *
 * Registers a transport which can be used as output to extract the data out of
 * LTTng. The module calling this registration function must ensure that no
 * trap-inducing code will be executed by the transport functions. E.g.
 * vmalloc_sync_all() must be called between a vmalloc and the moment the memory
 * is made visible to the transport function. This registration acts as a
 * vmalloc_sync_all. Therefore, only if the module allocates virtual memory
 * after its registration must it synchronize the TLBs.
 */
void ltt_transport_register(struct ltt_transport *transport)
{
	/*
	 * Make sure no page fault can be triggered by the module about to be
	 * registered. We deal with this here so we don't have to call
	 * vmalloc_sync_all() in each module's init.
	 */
//ust//	vmalloc_sync_all();

	pthread_mutex_lock(&ltt_transport_mutex);
	cds_list_add_tail(&transport->node, &ltt_transport_list);
	pthread_mutex_unlock(&ltt_transport_mutex);
}

/**
 * ltt_transport_unregister - LTT transport unregistration
 * @transport: transport structure
 */
void ltt_transport_unregister(struct ltt_transport *transport)
{
	pthread_mutex_lock(&ltt_transport_mutex);
	cds_list_del(&transport->node);
	pthread_mutex_unlock(&ltt_transport_mutex);
}

static inline int is_channel_overwrite(enum ltt_channels chan,
	enum trace_mode mode)
{
	switch (mode) {
	case LTT_TRACE_NORMAL:
		return 0;
	case LTT_TRACE_FLIGHT:
		switch (chan) {
		case LTT_CHANNEL_METADATA:
			return 0;
		default:
			return 1;
		}
	case LTT_TRACE_HYBRID:
		switch (chan) {
		case LTT_CHANNEL_METADATA:
			return 0;
		default:
			return 1;
		}
	default:
		return 0;
	}
}

static void trace_async_wakeup(struct ust_trace *trace)
{
	int i;
	struct ust_channel *chan;

	/* Must check each channel for pending read wakeup */
	for (i = 0; i < trace->nr_channels; i++) {
		chan = &trace->channels[i];
		if (chan->active)
			trace->ops->wakeup_channel(chan);
	}
}

//ust// /* Timer to send async wakeups to the readers */
//ust// static void async_wakeup(unsigned long data)
//ust// {
//ust// 	struct ust_trace *trace;
//ust// 
//ust// 	/*
//ust// 	 * PREEMPT_RT does not allow spinlocks to be taken within preempt
//ust// 	 * disable sections (spinlock taken in wake_up). However, mainline won't
//ust// 	 * allow mutex to be taken in interrupt context. Ugly.
//ust// 	 * A proper way to do this would be to turn the timer into a
//ust// 	 * periodically woken up thread, but it adds to the footprint.
//ust// 	 */
//ust// #ifndef CONFIG_PREEMPT_RT
//ust// 	rcu_read_lock_sched();
//ust// #else
//ust// 	ltt_lock_traces();
//ust// #endif
//ust// 	cds_list_for_each_entry_rcu(trace, &ltt_traces.head, list) {
//ust// 		trace_async_wakeup(trace);
//ust// 	}
//ust// #ifndef CONFIG_PREEMPT_RT
//ust// 	rcu_read_unlock_sched();
//ust// #else
//ust// 	ltt_unlock_traces();
//ust// #endif
//ust// 
//ust// 	mod_timer(&ltt_async_wakeup_timer, jiffies + LTT_PERCPU_TIMER_INTERVAL);
//ust// }

/**
 * _ltt_trace_find - find a trace by given name.
 * trace_name: trace name
 *
 * Returns a pointer to the trace structure, NULL if not found.
 */
struct ust_trace *_ltt_trace_find(const char *trace_name)
{
	struct ust_trace *trace;

	cds_list_for_each_entry(trace, &ltt_traces.head, list)
		if (!strncmp(trace->trace_name, trace_name, NAME_MAX))
			return trace;

	return NULL;
}

/* _ltt_trace_find_setup :
 * find a trace in setup list by given name.
 *
 * Returns a pointer to the trace structure, NULL if not found.
 */
struct ust_trace *_ltt_trace_find_setup(const char *trace_name)
{
	struct ust_trace *trace;

	cds_list_for_each_entry(trace, &ltt_traces.setup_head, list)
		if (!strncmp(trace->trace_name, trace_name, NAME_MAX))
			return trace;

	return NULL;
}

/**
 * ltt_release_transport - Release an LTT transport
 * @kref : reference count on the transport
 */
void ltt_release_transport(struct urcu_ref *urcu_ref)
{
//ust// 	struct ust_trace *trace = container_of(kref,
//ust// 			struct ust_trace, ltt_transport_kref);
//ust// 	trace->ops->remove_dirs(trace);
}

/**
 * ltt_release_trace - Release a LTT trace
 * @kref : reference count on the trace
 */
void ltt_release_trace(struct urcu_ref *urcu_ref)
{
	struct ust_trace *trace = _ust_container_of(urcu_ref,
			struct ust_trace, urcu_ref);
	ltt_channels_trace_free(trace->channels);
	free(trace);
}

static inline void prepare_chan_size_num(unsigned int *subbuf_size,
					 unsigned int *n_subbufs)
{
	/* Make sure the subbuffer size is larger than a page */
	*subbuf_size = max_t(unsigned int, *subbuf_size, PAGE_SIZE);

	/* round to next power of 2 */
	*subbuf_size = 1 << get_count_order(*subbuf_size);
	*n_subbufs = 1 << get_count_order(*n_subbufs);

	/* Subbuf size and number must both be power of two */
	WARN_ON(hweight32(*subbuf_size) != 1);
	WARN_ON(hweight32(*n_subbufs) != 1);
}

int _ltt_trace_setup(const char *trace_name)
{
	int err = 0;
	struct ust_trace *new_trace = NULL;
	int metadata_index;
	unsigned int chan;
	enum ltt_channels chantype;

	if (_ltt_trace_find_setup(trace_name)) {
		ERR("Trace name %s already used", trace_name);
		err = -EEXIST;
		goto traces_error;
	}

	if (_ltt_trace_find(trace_name)) {
		ERR("Trace name %s already used", trace_name);
		err = -EEXIST;
		goto traces_error;
	}

	new_trace = zmalloc(sizeof(struct ust_trace));
	if (!new_trace) {
		ERR("Unable to allocate memory for trace %s", trace_name);
		err = -ENOMEM;
		goto traces_error;
	}
	strncpy(new_trace->trace_name, trace_name, NAME_MAX);
	new_trace->channels = ltt_channels_trace_alloc(&new_trace->nr_channels,
				ust_channels_overwrite_by_default,
				ust_channels_request_collection_by_default, 1);
	if (!new_trace->channels) {
		ERR("Unable to allocate memory for chaninfo  %s\n", trace_name);
		err = -ENOMEM;
		goto trace_free;
	}

	/*
	 * Force metadata channel to active, no overwrite.
	 */
	metadata_index = ltt_channels_get_index_from_name("metadata");
	WARN_ON(metadata_index < 0);
	new_trace->channels[metadata_index].overwrite = 0;
	new_trace->channels[metadata_index].active = 1;

	/*
	 * Set hardcoded tracer defaults for some channels
	 */
	for (chan = 0; chan < new_trace->nr_channels; chan++) {
		if (!(new_trace->channels[chan].active))
			continue;

		chantype = get_channel_type_from_name(
			ltt_channels_get_name_from_index(chan));
		new_trace->channels[chan].subbuf_size =
			chan_infos[chantype].def_subbufsize;
		new_trace->channels[chan].subbuf_cnt =
			chan_infos[chantype].def_subbufcount;
	}

	cds_list_add(&new_trace->list, &ltt_traces.setup_head);
	return 0;

trace_free:
	free(new_trace);
traces_error:
	return err;
}


int ltt_trace_setup(const char *trace_name)
{
	int ret;
	ltt_lock_traces();
	ret = _ltt_trace_setup(trace_name);
	ltt_unlock_traces();
	return ret;
}

/* must be called from within a traces lock. */
static void _ltt_trace_free(struct ust_trace *trace)
{
	cds_list_del(&trace->list);
	free(trace);
}

int ltt_trace_set_type(const char *trace_name, const char *trace_type)
{
	int err = 0;
	struct ust_trace *trace;
	struct ltt_transport *tran_iter, *transport = NULL;

	ltt_lock_traces();

	trace = _ltt_trace_find_setup(trace_name);
	if (!trace) {
		ERR("Trace not found %s", trace_name);
		err = -ENOENT;
		goto traces_error;
	}

	pthread_mutex_lock(&ltt_transport_mutex);
	cds_list_for_each_entry(tran_iter, &ltt_transport_list, node) {
		if (!strcmp(tran_iter->name, trace_type)) {
			transport = tran_iter;
			break;
		}
	}
	pthread_mutex_unlock(&ltt_transport_mutex);

	if (!transport) {
		ERR("Transport %s is not present", trace_type);
		err = -EINVAL;
		goto traces_error;
	}

	trace->transport = transport;

traces_error:
	ltt_unlock_traces();
	return err;
}

int ltt_trace_set_channel_subbufsize(const char *trace_name,
		const char *channel_name, unsigned int size)
{
	int err = 0;
	struct ust_trace *trace;
	int index;

	ltt_lock_traces();

	trace = _ltt_trace_find_setup(trace_name);
	if (!trace) {
		ERR("Trace not found %s", trace_name);
		err = -ENOENT;
		goto traces_error;
	}

	index = ltt_channels_get_index_from_name(channel_name);
	if (index < 0) {
		ERR("Channel %s not found", channel_name);
		err = -ENOENT;
		goto traces_error;
	}
	trace->channels[index].subbuf_size = size;

traces_error:
	ltt_unlock_traces();
	return err;
}

int ltt_trace_set_channel_subbufcount(const char *trace_name,
		const char *channel_name, unsigned int cnt)
{
	int err = 0;
	struct ust_trace *trace;
	int index;

	ltt_lock_traces();

	trace = _ltt_trace_find_setup(trace_name);
	if (!trace) {
		ERR("Trace not found %s", trace_name);
		err = -ENOENT;
		goto traces_error;
	}

	index = ltt_channels_get_index_from_name(channel_name);
	if (index < 0) {
		ERR("Channel %s not found", channel_name);
		err = -ENOENT;
		goto traces_error;
	}
	trace->channels[index].subbuf_cnt = cnt;

traces_error:
	ltt_unlock_traces();
	return err;
}

int ltt_trace_set_channel_enable(const char *trace_name,
		const char *channel_name, unsigned int enable)
{
	int err = 0;
	struct ust_trace *trace;
	int index;

	ltt_lock_traces();

	trace = _ltt_trace_find_setup(trace_name);
	if (!trace) {
		ERR("Trace not found %s", trace_name);
		err = -ENOENT;
		goto traces_error;
	}

	/*
	 * Datas in metadata channel(marker info) is necessary to be able to
	 * read the trace, we always enable this channel.
	 */
	if (!enable && !strcmp(channel_name, "metadata")) {
		ERR("Trying to disable metadata channel");
		err = -EINVAL;
		goto traces_error;
	}

	index = ltt_channels_get_index_from_name(channel_name);
	if (index < 0) {
		ERR("Channel %s not found", channel_name);
		err = -ENOENT;
		goto traces_error;
	}

	trace->channels[index].active = enable;

traces_error:
	ltt_unlock_traces();
	return err;
}

int ltt_trace_set_channel_overwrite(const char *trace_name,
		const char *channel_name, unsigned int overwrite)
{
	int err = 0;
	struct ust_trace *trace;
	int index;

	ltt_lock_traces();

	trace = _ltt_trace_find_setup(trace_name);
	if (!trace) {
		ERR("Trace not found %s", trace_name);
		err = -ENOENT;
		goto traces_error;
	}

	/*
	 * Always put the metadata channel in non-overwrite mode :
	 * This is a very low traffic channel and it can't afford to have its
	 * data overwritten : this data (marker info) is necessary to be
	 * able to read the trace.
	 */
	if (overwrite && !strcmp(channel_name, "metadata")) {
		ERR("Trying to set metadata channel to overwrite mode");
		err = -EINVAL;
		goto traces_error;
	}

	index = ltt_channels_get_index_from_name(channel_name);
	if (index < 0) {
		ERR("Channel %s not found", channel_name);
		err = -ENOENT;
		goto traces_error;
	}

	trace->channels[index].overwrite = overwrite;

traces_error:
	ltt_unlock_traces();
	return err;
}

int ltt_trace_alloc(const char *trace_name)
{
	int err = 0;
	struct ust_trace *trace;
	unsigned int subbuf_size, subbuf_cnt;
//ust//	unsigned long flags;
	int chan;
	const char *channel_name;

	ltt_lock_traces();

	if (_ltt_trace_find(trace_name)) { /* Trace already allocated */
		err = 1;
		goto traces_error;
	}

	trace = _ltt_trace_find_setup(trace_name);
	if (!trace) {
		ERR("Trace not found %s", trace_name);
		err = -ENOENT;
		goto traces_error;
	}

	urcu_ref_init(&trace->urcu_ref);
	urcu_ref_init(&trace->ltt_transport_urcu_ref);
//ust//	init_waitqueue_head(&trace->urcu_ref_wq);
	trace->active = 0;
//ust//	get_trace_clock();
	trace->freq_scale = trace_clock_freq_scale();

	if (!trace->transport) {
		ERR("Transport is not set");
		err = -EINVAL;
		goto transport_error;
	}
//ust//	if (!try_module_get(trace->transport->owner)) {
//ust//		ERR("Can't lock transport module");
//ust//		err = -ENODEV;
//ust//		goto transport_error;
//ust//	}
	trace->ops = &trace->transport->ops;

//ust//	err = trace->ops->create_dirs(trace);
//ust//	if (err) {
//ust//		ERR("Can't create dir for trace %s", trace_name);
//ust//		goto dirs_error;
//ust//	}

//ust//	local_irq_save(flags);
	trace->start_freq = trace_clock_frequency();
	trace->start_tsc = trace_clock_read64();
	gettimeofday(&trace->start_time, NULL); //ust// changed /* FIXME: is this ok? */
//ust//	local_irq_restore(flags);

	for (chan = 0; chan < trace->nr_channels; chan++) {
		if (!(trace->channels[chan].active))
			continue;

		channel_name = ltt_channels_get_name_from_index(chan);
		WARN_ON(!channel_name);
		subbuf_size = trace->channels[chan].subbuf_size;
		subbuf_cnt = trace->channels[chan].subbuf_cnt;
		prepare_chan_size_num(&subbuf_size, &subbuf_cnt);
		err = trace->ops->create_channel(trace_name, trace,
				channel_name,
				&trace->channels[chan],
				subbuf_size,
				subbuf_cnt,
				trace->channels[chan].overwrite);
		if (err != 0) {
			ERR("Cannot create channel %s", channel_name);
			goto create_channel_error;
		}
	}

	cds_list_del(&trace->list);
//ust//	if (cds_list_empty(&ltt_traces.head)) {
//ust//		mod_timer(&ltt_async_wakeup_timer,
//ust//				jiffies + LTT_PERCPU_TIMER_INTERVAL);
//ust//		set_kernel_trace_flag_all_tasks();
//ust//	}
	cds_list_add_rcu(&trace->list, &ltt_traces.head);
//ust//	synchronize_sched();

	ltt_unlock_traces();

	return 0;

create_channel_error:
	for (chan--; chan >= 0; chan--)
		if (trace->channels[chan].active)
			trace->ops->remove_channel(&trace->channels[chan]);

//ust// dirs_error:
//ust//	module_put(trace->transport->owner);
transport_error:
//ust//	put_trace_clock();
traces_error:
	ltt_unlock_traces();
	return err;
}

/*
 * It is worked as a wrapper for current version of ltt_control.ko.
 * We will make a new ltt_control based on debugfs, and control each channel's
 * buffer.
 */
//ust// static int ltt_trace_create(const char *trace_name, const char *trace_type,
//ust// 		enum trace_mode mode,
//ust// 		unsigned int subbuf_size_low, unsigned int n_subbufs_low,
//ust// 		unsigned int subbuf_size_med, unsigned int n_subbufs_med,
//ust// 		unsigned int subbuf_size_high, unsigned int n_subbufs_high)
//ust// {
//ust// 	int err = 0;
//ust// 
//ust// 	err = ltt_trace_setup(trace_name);
//ust// 	if (IS_ERR_VALUE(err))
//ust// 		return err;
//ust// 
//ust// 	err = ltt_trace_set_type(trace_name, trace_type);
//ust// 	if (IS_ERR_VALUE(err))
//ust// 		return err;
//ust// 
//ust// 	err = ltt_trace_alloc(trace_name);
//ust// 	if (IS_ERR_VALUE(err))
//ust// 		return err;
//ust// 
//ust// 	return err;
//ust// }

/* Must be called while sure that trace is in the list. */
static int _ltt_trace_destroy(struct ust_trace *trace)
{
	int err = -EPERM;

	if (trace == NULL) {
		err = -ENOENT;
		goto traces_error;
	}
	if (trace->active) {
		ERR("Can't destroy trace %s : tracer is active", trace->trace_name);
		err = -EBUSY;
		goto active_error;
	}
	/* Everything went fine */
	cds_list_del_rcu(&trace->list);
	synchronize_rcu();
	if (cds_list_empty(&ltt_traces.head)) {
//ust//		clear_kernel_trace_flag_all_tasks();
		/*
		 * We stop the asynchronous delivery of reader wakeup, but
		 * we must make one last check for reader wakeups pending
		 * later in __ltt_trace_destroy.
		 */
//ust//		del_timer_sync(&ltt_async_wakeup_timer);
	}
	return 0;

	/* error handling */
active_error:
traces_error:
	return err;
}

/* Sleepable part of the destroy */
static void __ltt_trace_destroy(struct ust_trace *trace, int drop)
{
	int i;
	struct ust_channel *chan;

	if(!drop) {
		for (i = 0; i < trace->nr_channels; i++) {
			chan = &trace->channels[i];
			if (chan->active)
				trace->ops->finish_channel(chan);
		}
	}

	/*
	 * The currently destroyed trace is not in the trace list anymore,
	 * so it's safe to call the async wakeup ourself. It will deliver
	 * the last subbuffers.
	 */
	trace_async_wakeup(trace);

	for (i = 0; i < trace->nr_channels; i++) {
		chan = &trace->channels[i];
		if (chan->active)
			trace->ops->remove_channel(chan);
	}

	urcu_ref_put(&trace->ltt_transport_urcu_ref, ltt_release_transport);

//ust//	module_put(trace->transport->owner);

	/*
	 * Wait for lttd readers to release the files, therefore making sure
	 * the last subbuffers have been read.
	 */
//ust//	if (atomic_read(&trace->kref.refcount) > 1) {
//ust//		int ret = 0;
//ust//		__wait_event_interruptible(trace->kref_wq,
//ust//			(atomic_read(&trace->kref.refcount) == 1), ret);
//ust//	}
	urcu_ref_put(&trace->urcu_ref, ltt_release_trace);
}

int ltt_trace_destroy(const char *trace_name, int drop)
{
	int err = 0;
	struct ust_trace *trace;

	ltt_lock_traces();

	trace = _ltt_trace_find(trace_name);
	if (trace) {
		err = _ltt_trace_destroy(trace);
		if (err)
			goto error;

		ltt_unlock_traces();

		__ltt_trace_destroy(trace, drop);
//ust//		put_trace_clock();

		return 0;
	}

	trace = _ltt_trace_find_setup(trace_name);
	if (trace) {
		_ltt_trace_free(trace);
		ltt_unlock_traces();
		return 0;
	}

	err = -ENOENT;

	/* Error handling */
error:
	ltt_unlock_traces();
	return err;
}

/* must be called from within a traces lock. */
static int _ltt_trace_start(struct ust_trace *trace)
{
	int err = 0;

	if (trace == NULL) {
		err = -ENOENT;
		goto traces_error;
	}
	if (trace->active)
		DBG("Tracing already active for trace %s", trace->trace_name);
//ust//	if (!try_module_get(ltt_run_filter_owner)) {
//ust//		err = -ENODEV;
//ust//		ERR("Cannot lock filter module");
//ust//		goto get_ltt_run_filter_error;
//ust//	}
	trace->active = 1;
	/* Read by trace points without protection : be careful */
	ltt_traces.num_active_traces++;
	return err;

	/* error handling */
//ust// get_ltt_run_filter_error:
traces_error:
	return err;
}

int ltt_trace_start(const char *trace_name)
{
	int err = 0;
	struct ust_trace *trace;

	ltt_lock_traces();

	trace = _ltt_trace_find(trace_name);
	err = _ltt_trace_start(trace);
	if (err)
		goto no_trace;

	ltt_unlock_traces();

	/*
	 * Call the process-wide state dump.
	 * Notice that there is no protection on the trace : that's exactly
	 * why we iterate on the list and check for trace equality instead of
	 * directly using this trace handle inside the logging function: we want
	 * to record events only in a single trace in the trace session list.
	 */

	ltt_dump_marker_state(trace);

//ust//	if (!try_module_get(ltt_statedump_owner)) {
//ust//		err = -ENODEV;
//ust//		ERR("Cannot lock state dump module");
//ust//	} else {
		ltt_statedump_functor(trace);
//ust//		module_put(ltt_statedump_owner);
//ust//	}

	return err;

	/* Error handling */
no_trace:
	ltt_unlock_traces();
	return err;
}

/* must be called from within traces lock */
static int _ltt_trace_stop(struct ust_trace *trace)
{
	int err = -EPERM;

	if (trace == NULL) {
		err = -ENOENT;
		goto traces_error;
	}
	if (!trace->active)
		DBG("LTT : Tracing not active for trace %s", trace->trace_name);
	if (trace->active) {
		trace->active = 0;
		ltt_traces.num_active_traces--;
//ust//		synchronize_sched(); /* Wait for each tracing to be finished */
	}
//ust//	module_put(ltt_run_filter_owner);
	/* Everything went fine */
	return 0;

	/* Error handling */
traces_error:
	return err;
}

int ltt_trace_stop(const char *trace_name)
{
	int err = 0;
	struct ust_trace *trace;

	ltt_lock_traces();
	trace = _ltt_trace_find(trace_name);
	err = _ltt_trace_stop(trace);
	ltt_unlock_traces();
	return err;
}

/**
 * ltt_filter_control - Trace filter control in-kernel API
 * @msg: Action to perform on the filter
 * @trace_name: Trace on which the action must be done
 */
int ltt_filter_control(enum ltt_filter_control_msg msg, const char *trace_name)
{
	int err;
	struct ust_trace *trace;

	DBG("ltt_filter_control : trace %s", trace_name);
	ltt_lock_traces();
	trace = _ltt_trace_find(trace_name);
	if (trace == NULL) {
		ERR("Trace does not exist. Cannot proxy control request");
		err = -ENOENT;
		goto trace_error;
	}
//ust//	if (!try_module_get(ltt_filter_control_owner)) {
//ust//		err = -ENODEV;
//ust//		goto get_module_error;
//ust//	}
	switch (msg) {
	case LTT_FILTER_DEFAULT_ACCEPT:
		DBG("Proxy filter default accept %s", trace_name);
		err = (*ltt_filter_control_functor)(msg, trace);
		break;
	case LTT_FILTER_DEFAULT_REJECT:
		DBG("Proxy filter default reject %s", trace_name);
		err = (*ltt_filter_control_functor)(msg, trace);
		break;
	default:
		err = -EPERM;
	}
//ust//	module_put(ltt_filter_control_owner);

//ust// get_module_error:
trace_error:
	ltt_unlock_traces();
	return err;
}