[lttng-modules.git] / ltt-events.c

/*
 * ltt-events.c
 *
 * Copyright 2010 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * Holds LTTng per-session event registry.
 */

#include <linux/module.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include "wrapper/vmalloc.h"	/* for wrapper_vmalloc_sync_all() */
#include "ltt-events.h"

static LIST_HEAD(sessions);
static LIST_HEAD(ltt_transport_list);
static DEFINE_MUTEX(sessions_mutex);
static struct kmem_cache *event_cache;

static void synchronize_trace(void)
{
	synchronize_sched();
#ifdef CONFIG_PREEMPT_RT
	synchronize_rcu();
#endif
}

struct ltt_session *ltt_session_create(void)
{
	struct ltt_session *session;

	mutex_lock(&sessions_mutex);
	session = kzalloc(sizeof(struct ltt_session), GFP_KERNEL);
	if (!session)
		return NULL;
	INIT_LIST_HEAD(&session->chan);
	INIT_LIST_HEAD(&session->events);
	list_add(&session->list, &sessions);
	mutex_unlock(&sessions_mutex);
	return session;
}

void ltt_session_destroy(struct ltt_session *session)
{
	struct ltt_channel *chan, *tmpchan;
	struct ltt_event *event, *tmpevent;
	int ret;

	mutex_lock(&sessions_mutex);
	ACCESS_ONCE(session->active) = 0;
	list_for_each_entry(event, &session->events, list) {
		ret = _ltt_event_unregister(event);
		WARN_ON(ret);
	}
	synchronize_trace();	/* Wait for in-flight events to complete */
	list_for_each_entry_safe(event, tmpevent, &session->events, list)
		_ltt_event_destroy(event);
	list_for_each_entry_safe(chan, tmpchan, &session->chan, list)
		_ltt_channel_destroy(chan);
	list_del(&session->list);
	mutex_unlock(&sessions_mutex);
	kfree(session);
}

int ltt_session_start(struct ltt_session *session)
{
	int ret = 0;

	mutex_lock(&sessions_mutex);
	if (session->active) {
		ret = -EBUSY;
		goto end;
	}
	ACCESS_ONCE(session->active) = 1;
	synchronize_trace();	/* Wait for in-flight events to complete */
end:
	mutex_unlock(&sessions_mutex);
	return ret;
}

int ltt_session_stop(struct ltt_session *session)
{
	int ret = 0;

	mutex_lock(&sessions_mutex);
	if (!session->active) {
		ret = -EBUSY;
		goto end;
	}
	ACCESS_ONCE(session->active) = 0;
	synchronize_trace();	/* Wait for in-flight events to complete */
end:
	mutex_unlock(&sessions_mutex);
	return ret;
}

static struct ltt_transport *ltt_transport_find(const char *name)
{
	struct ltt_transport *transport;

	list_for_each_entry(transport, &ltt_transport_list, node) {
		if (!strcmp(transport->name, name))
			return transport;
	}
	return NULL;
}

struct ltt_channel *ltt_channel_create(struct ltt_session *session,
				       const char *transport_name,
				       void *buf_addr,
				       size_t subbuf_size, size_t num_subbuf,
				       unsigned int switch_timer_interval,
				       unsigned int read_timer_interval)
{
	struct ltt_channel *chan;
	struct ltt_transport *transport;

	mutex_lock(&sessions_mutex);
	if (session->active) {
		printk(KERN_WARNING "LTTng refusing to add channel to active session\n");
		goto active;	/* Refuse to add channel to active session */
	}
	transport = ltt_transport_find(transport_name);
	if (!transport) {
		printk(KERN_WARNING "LTTng transport %s not found\n",
		       transport_name);
		goto notransport;
	}
	chan = kzalloc(sizeof(struct ltt_channel), GFP_KERNEL);
	if (!chan)
		goto nomem;
	chan->session = session;
	init_waitqueue_head(&chan->notify_wait);
	chan->chan = transport->ops.channel_create("[lttng]", session, buf_addr,
			subbuf_size, num_subbuf, switch_timer_interval,
			read_timer_interval);
	if (!chan->chan)
		goto create_error;
	chan->ops = &transport->ops;
	list_add(&chan->list, &session->chan);
	mutex_unlock(&sessions_mutex);
	return chan;

create_error:
	kfree(chan);
nomem:
notransport:
active:
	mutex_unlock(&sessions_mutex);
	return NULL;
}

/*
 * Only used internally at session destruction.
 */
void _ltt_channel_destroy(struct ltt_channel *chan)
{
	chan->ops->channel_destroy(chan->chan);
	list_del(&chan->list);
	kfree(chan);
}

/*
 * Supports event creation while tracing session is active.
 */
struct ltt_event *ltt_event_create(struct ltt_channel *chan, char *name,
				   enum instrum_type itype,
				   const struct lttng_event_desc *event_desc,
				   void *filter)
{
	struct ltt_event *event;
	int ret;

	mutex_lock(&sessions_mutex);
	if (chan->free_event_id == -1UL)
		goto full;
	/*
	 * This is O(n^2) (for each event, the loop is called at event
	 * creation). Might require a hash if we have lots of events.
	 */
	list_for_each_entry(event, &chan->session->events, list)
		if (!strcmp(event->desc->name, name))
			goto exist;
	event = kmem_cache_zalloc(event_cache, GFP_KERNEL);
	if (!event)
		goto cache_error;
	event->chan = chan;
	event->desc = event_desc;
	event->filter = filter;
	event->id = chan->free_event_id++;
	event->itype = itype;
	/* Populate ltt_event structure before tracepoint registration. */
	smp_wmb();
	switch (itype) {
	case INSTRUM_TRACEPOINTS:
		ret = tracepoint_probe_register(name, event_desc->probe_callback,
						event);
		if (ret)
			goto register_error;
		break;
	default:
		WARN_ON_ONCE(1);
	}
	list_add(&event->list, &chan->session->events);
	mutex_unlock(&sessions_mutex);
	return event;

register_error:
	kmem_cache_free(event_cache, event);
cache_error:
exist:
full:
	mutex_unlock(&sessions_mutex);
	return NULL;
}

/*
 * Only used internally at session destruction.
 */
int _ltt_event_unregister(struct ltt_event *event)
{
	int ret = -EINVAL;

	switch (event->itype) {
	case INSTRUM_TRACEPOINTS:
		ret = tracepoint_probe_unregister(event->desc->name,
						  event->desc->probe_callback,
						  event);
		if (ret)
			return ret;
		break;
	default:
		WARN_ON_ONCE(1);
	}
	return ret;
}

/*
 * Only used internally at session destruction.
 */
void _ltt_event_destroy(struct ltt_event *event)
{
	ltt_event_put(event->desc);
	list_del(&event->list);
	kmem_cache_free(event_cache, event);
}

/**
 * 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.
	 */
	wrapper_vmalloc_sync_all();

	mutex_lock(&sessions_mutex);
	list_add_tail(&transport->node, &ltt_transport_list);
	mutex_unlock(&sessions_mutex);
}
EXPORT_SYMBOL_GPL(ltt_transport_register);

/**
 * ltt_transport_unregister - LTT transport unregistration
 * @transport: transport structure
 */
void ltt_transport_unregister(struct ltt_transport *transport)
{
	mutex_lock(&sessions_mutex);
	list_del(&transport->node);
	mutex_unlock(&sessions_mutex);
}
EXPORT_SYMBOL_GPL(ltt_transport_unregister);


static int __init ltt_events_init(void)
{
	int ret;

	event_cache = KMEM_CACHE(ltt_event, 0);
	if (!event_cache)
		return -ENOMEM;
	ret = ltt_debugfs_abi_init();
	if (ret)
		goto error_abi;
	return 0;
error_abi:
	kmem_cache_destroy(event_cache);
	return ret;
}

module_init(ltt_events_init);

static void __exit ltt_events_exit(void)
{
	struct ltt_session *session, *tmpsession;

	ltt_debugfs_abi_exit();
	list_for_each_entry_safe(session, tmpsession, &sessions, list)
		ltt_session_destroy(session);
	kmem_cache_destroy(event_cache);
}

module_exit(ltt_events_exit);

MODULE_LICENSE("GPL and additional rights");
MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
MODULE_DESCRIPTION("LTTng Events");
Commit	Line	Data
	1	/*
	2	* ltt-events.c
	3	*
	4	* Copyright 2010 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	5	*
	6	* Holds LTTng per-session event registry.
	7	*/
	8
	9	#include <linux/module.h>
	10	#include <linux/list.h>
	11	#include <linux/mutex.h>
	12	#include <linux/sched.h>
	13	#include <linux/slab.h>
	14	#include "wrapper/vmalloc.h" /* for wrapper_vmalloc_sync_all() */
	15	#include "ltt-events.h"
	16
	17	static LIST_HEAD(sessions);
	18	static LIST_HEAD(ltt_transport_list);
	19	static DEFINE_MUTEX(sessions_mutex);
	20	static struct kmem_cache *event_cache;
	21
	22	static void synchronize_trace(void)
	23	{
	24	synchronize_sched();
	25	#ifdef CONFIG_PREEMPT_RT
	26	synchronize_rcu();
	27	#endif
	28	}
	29
	30	struct ltt_session *ltt_session_create(void)
	31	{
	32	struct ltt_session *session;
	33
	34	mutex_lock(&sessions_mutex);
	35	session = kzalloc(sizeof(struct ltt_session), GFP_KERNEL);
	36	if (!session)
	37	return NULL;
	38	INIT_LIST_HEAD(&session->chan);
	39	INIT_LIST_HEAD(&session->events);
	40	list_add(&session->list, &sessions);
	41	mutex_unlock(&sessions_mutex);
	42	return session;
	43	}
	44
	45	void ltt_session_destroy(struct ltt_session *session)
	46	{
	47	struct ltt_channel chan, tmpchan;
	48	struct ltt_event event, tmpevent;
	49	int ret;
	50
	51	mutex_lock(&sessions_mutex);
	52	ACCESS_ONCE(session->active) = 0;
	53	list_for_each_entry(event, &session->events, list) {
	54	ret = _ltt_event_unregister(event);
	55	WARN_ON(ret);
	56	}
	57	synchronize_trace(); /* Wait for in-flight events to complete */
	58	list_for_each_entry_safe(event, tmpevent, &session->events, list)
	59	_ltt_event_destroy(event);
	60	list_for_each_entry_safe(chan, tmpchan, &session->chan, list)
	61	_ltt_channel_destroy(chan);
	62	list_del(&session->list);
	63	mutex_unlock(&sessions_mutex);
	64	kfree(session);
	65	}
	66
	67	int ltt_session_start(struct ltt_session *session)
	68	{
	69	int ret = 0;
	70
	71	mutex_lock(&sessions_mutex);
	72	if (session->active) {
	73	ret = -EBUSY;
	74	goto end;
	75	}
	76	ACCESS_ONCE(session->active) = 1;
	77	synchronize_trace(); /* Wait for in-flight events to complete */
	78	end:
	79	mutex_unlock(&sessions_mutex);
	80	return ret;
	81	}
	82
	83	int ltt_session_stop(struct ltt_session *session)
	84	{
	85	int ret = 0;
	86
	87	mutex_lock(&sessions_mutex);
	88	if (!session->active) {
	89	ret = -EBUSY;
	90	goto end;
	91	}
	92	ACCESS_ONCE(session->active) = 0;
	93	synchronize_trace(); /* Wait for in-flight events to complete */
	94	end:
	95	mutex_unlock(&sessions_mutex);
	96	return ret;
	97	}
	98
	99	static struct ltt_transport ltt_transport_find(const char name)
	100	{
	101	struct ltt_transport *transport;
	102
	103	list_for_each_entry(transport, &ltt_transport_list, node) {
	104	if (!strcmp(transport->name, name))
	105	return transport;
	106	}
	107	return NULL;
	108	}
	109
	110	struct ltt_channel ltt_channel_create(struct ltt_session session,
	111	const char *transport_name,
	112	void *buf_addr,
	113	size_t subbuf_size, size_t num_subbuf,
	114	unsigned int switch_timer_interval,
	115	unsigned int read_timer_interval)
	116	{
	117	struct ltt_channel *chan;
	118	struct ltt_transport *transport;
	119
	120	mutex_lock(&sessions_mutex);
	121	if (session->active) {
	122	printk(KERN_WARNING "LTTng refusing to add channel to active session\n");
	123	goto active; /* Refuse to add channel to active session */
	124	}
	125	transport = ltt_transport_find(transport_name);
	126	if (!transport) {
	127	printk(KERN_WARNING "LTTng transport %s not found\n",
	128	transport_name);
	129	goto notransport;
	130	}
	131	chan = kzalloc(sizeof(struct ltt_channel), GFP_KERNEL);
	132	if (!chan)
	133	goto nomem;
	134	chan->session = session;
	135	init_waitqueue_head(&chan->notify_wait);
	136	chan->chan = transport->ops.channel_create("[lttng]", session, buf_addr,
	137	subbuf_size, num_subbuf, switch_timer_interval,
	138	read_timer_interval);
	139	if (!chan->chan)
	140	goto create_error;
	141	chan->ops = &transport->ops;
	142	list_add(&chan->list, &session->chan);
	143	mutex_unlock(&sessions_mutex);
	144	return chan;
	145
	146	create_error:
	147	kfree(chan);
	148	nomem:
	149	notransport:
	150	active:
	151	mutex_unlock(&sessions_mutex);
	152	return NULL;
	153	}
	154
	155	/*
	156	* Only used internally at session destruction.
	157	*/
	158	void _ltt_channel_destroy(struct ltt_channel *chan)
	159	{
	160	chan->ops->channel_destroy(chan->chan);
	161	list_del(&chan->list);
	162	kfree(chan);
	163	}
	164
	165	/*
	166	* Supports event creation while tracing session is active.
	167	*/
	168	struct ltt_event ltt_event_create(struct ltt_channel chan, char *name,
	169	enum instrum_type itype,
	170	const struct lttng_event_desc *event_desc,
	171	void *filter)
	172	{
	173	struct ltt_event *event;
	174	int ret;
	175
	176	mutex_lock(&sessions_mutex);
	177	if (chan->free_event_id == -1UL)
	178	goto full;
	179	/*
	180	* This is O(n^2) (for each event, the loop is called at event
	181	* creation). Might require a hash if we have lots of events.
	182	*/
	183	list_for_each_entry(event, &chan->session->events, list)
	184	if (!strcmp(event->desc->name, name))
	185	goto exist;
	186	event = kmem_cache_zalloc(event_cache, GFP_KERNEL);
	187	if (!event)
	188	goto cache_error;
	189	event->chan = chan;
	190	event->desc = event_desc;
	191	event->filter = filter;
	192	event->id = chan->free_event_id++;
	193	event->itype = itype;
	194	/* Populate ltt_event structure before tracepoint registration. */
	195	smp_wmb();
	196	switch (itype) {
	197	case INSTRUM_TRACEPOINTS:
	198	ret = tracepoint_probe_register(name, event_desc->probe_callback,
	199	event);
	200	if (ret)
	201	goto register_error;
	202	break;
	203	default:
	204	WARN_ON_ONCE(1);
	205	}
	206	list_add(&event->list, &chan->session->events);
	207	mutex_unlock(&sessions_mutex);
	208	return event;
	209
	210	register_error:
	211	kmem_cache_free(event_cache, event);
	212	cache_error:
	213	exist:
	214	full:
	215	mutex_unlock(&sessions_mutex);
	216	return NULL;
	217	}
	218
	219	/*
	220	* Only used internally at session destruction.
	221	*/
	222	int _ltt_event_unregister(struct ltt_event *event)
	223	{
	224	int ret = -EINVAL;
	225
	226	switch (event->itype) {
	227	case INSTRUM_TRACEPOINTS:
	228	ret = tracepoint_probe_unregister(event->desc->name,
	229	event->desc->probe_callback,
	230	event);
	231	if (ret)
	232	return ret;
	233	break;
	234	default:
	235	WARN_ON_ONCE(1);
	236	}
	237	return ret;
	238	}
	239
	240	/*
	241	* Only used internally at session destruction.
	242	*/
	243	void _ltt_event_destroy(struct ltt_event *event)
	244	{
	245	ltt_event_put(event->desc);
	246	list_del(&event->list);
	247	kmem_cache_free(event_cache, event);
	248	}
	249
	250	/**
	251	* ltt_transport_register - LTT transport registration
	252	* @transport: transport structure
	253	*
	254	* Registers a transport which can be used as output to extract the data out of
	255	* LTTng. The module calling this registration function must ensure that no
	256	* trap-inducing code will be executed by the transport functions. E.g.
	257	* vmalloc_sync_all() must be called between a vmalloc and the moment the memory
	258	* is made visible to the transport function. This registration acts as a
	259	* vmalloc_sync_all. Therefore, only if the module allocates virtual memory
	260	* after its registration must it synchronize the TLBs.
	261	*/
	262	void ltt_transport_register(struct ltt_transport *transport)
	263	{
	264	/*
	265	* Make sure no page fault can be triggered by the module about to be
	266	* registered. We deal with this here so we don't have to call
	267	* vmalloc_sync_all() in each module's init.
	268	*/
	269	wrapper_vmalloc_sync_all();
	270
	271	mutex_lock(&sessions_mutex);
	272	list_add_tail(&transport->node, &ltt_transport_list);
	273	mutex_unlock(&sessions_mutex);
	274	}
	275	EXPORT_SYMBOL_GPL(ltt_transport_register);
	276
	277	/**
	278	* ltt_transport_unregister - LTT transport unregistration
	279	* @transport: transport structure
	280	*/
	281	void ltt_transport_unregister(struct ltt_transport *transport)
	282	{
	283	mutex_lock(&sessions_mutex);
	284	list_del(&transport->node);
	285	mutex_unlock(&sessions_mutex);
	286	}
	287	EXPORT_SYMBOL_GPL(ltt_transport_unregister);
	288
	289
	290	static int __init ltt_events_init(void)
	291	{
	292	int ret;
	293
	294	event_cache = KMEM_CACHE(ltt_event, 0);
	295	if (!event_cache)
	296	return -ENOMEM;
	297	ret = ltt_debugfs_abi_init();
	298	if (ret)
	299	goto error_abi;
	300	return 0;
	301	error_abi:
	302	kmem_cache_destroy(event_cache);
	303	return ret;
	304	}
	305
	306	module_init(ltt_events_init);
	307
	308	static void __exit ltt_events_exit(void)
	309	{
	310	struct ltt_session session, tmpsession;
	311
	312	ltt_debugfs_abi_exit();
	313	list_for_each_entry_safe(session, tmpsession, &sessions, list)
	314	ltt_session_destroy(session);
	315	kmem_cache_destroy(event_cache);
	316	}
	317
	318	module_exit(ltt_events_exit);
	319
	320	MODULE_LICENSE("GPL and additional rights");
	321	MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
	322	MODULE_DESCRIPTION("LTTng Events");