[deliverable/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 <linux/vmalloc.h>	/* For 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);
	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;
	}
	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;
	}
	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(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,
				       int overwrite, 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;
	char *transport_name;

	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_name = overwrite ? "relay-overwrite" : "relay-discard";
	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,
				   void *probe, 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->name, name))
			goto exist;
	event = kmem_cache_zalloc(event_cache, GFP_KERNEL);
	if (!event)
		goto cache_error;
	event->name = kmalloc(strlen(name) + 1, GFP_KERNEL);
	if (!event->name)
		goto name_error;
	strcpy(event->name, name);
	event->chan = chan;
	event->probe = probe;
	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, probe, 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:
	kfree(event->name);
name_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->name, event->probe,
						  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)
{
	kfree(event->name);
	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.
	 */
	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_probes_init();
	if (ret)
		goto error;
	ret = ltt_debugfs_abi_init();
	if (ret)
		goto error_abi;
	return 0;
error_abi:
	ltt_probes_exit();
error:
	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();
	ltt_probes_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 <linux/vmalloc.h> /* For 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	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	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	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(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	int overwrite, void *buf_addr,
	112	size_t subbuf_size, size_t num_subbuf,
	113	unsigned int switch_timer_interval,
	114	unsigned int read_timer_interval)
	115	{
	116	struct ltt_channel *chan;
	117	struct ltt_transport *transport;
	118	char *transport_name;
	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_name = overwrite ? "relay-overwrite" : "relay-discard";
	126	transport = ltt_transport_find(transport_name);
	127	if (!transport) {
	128	printk(KERN_WARNING "LTTng transport %s not found\n",
	129	transport_name);
	130	goto notransport;
	131	}
	132	chan = kzalloc(sizeof(struct ltt_channel), GFP_KERNEL);
	133	if (!chan)
	134	goto nomem;
	135	chan->session = session;
	136	init_waitqueue_head(&chan->notify_wait);
	137	chan->chan = transport->ops.channel_create("[lttng]", session, buf_addr,
	138	subbuf_size, num_subbuf, switch_timer_interval,
	139	read_timer_interval);
	140	if (!chan->chan)
	141	goto create_error;
	142	chan->ops = &transport->ops;
	143	list_add(&chan->list, &session->chan);
	144	mutex_unlock(&sessions_mutex);
	145	return chan;
	146
	147	create_error:
	148	kfree(chan);
	149	nomem:
	150	notransport:
	151	active:
	152	mutex_unlock(&sessions_mutex);
	153	return NULL;
	154	}
	155
	156	/*
	157	* Only used internally at session destruction.
	158	*/
	159	void _ltt_channel_destroy(struct ltt_channel *chan)
	160	{
	161	chan->ops->channel_destroy(chan->chan);
	162	list_del(&chan->list);
	163	kfree(chan);
	164	}
	165
	166	/*
	167	* Supports event creation while tracing session is active.
	168	*/
	169	struct ltt_event ltt_event_create(struct ltt_channel chan, char *name,
	170	enum instrum_type itype,
	171	void probe, 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->name, name))
	185	goto exist;
	186	event = kmem_cache_zalloc(event_cache, GFP_KERNEL);
	187	if (!event)
	188	goto cache_error;
	189	event->name = kmalloc(strlen(name) + 1, GFP_KERNEL);
	190	if (!event->name)
	191	goto name_error;
	192	strcpy(event->name, name);
	193	event->chan = chan;
	194	event->probe = probe;
	195	event->filter = filter;
	196	event->id = chan->free_event_id++;
	197	event->itype = itype;
	198	/* Populate ltt_event structure before tracepoint registration. */
	199	smp_wmb();
	200	switch (itype) {
	201	case INSTRUM_TRACEPOINTS:
	202	ret = tracepoint_probe_register(name, probe, event);
	203	if (ret)
	204	goto register_error;
	205	break;
	206	default:
	207	WARN_ON_ONCE(1);
	208	}
	209	list_add(&event->list, &chan->session->events);
	210	mutex_unlock(&sessions_mutex);
	211	return event;
	212
	213	register_error:
	214	kfree(event->name);
	215	name_error:
	216	kmem_cache_free(event_cache, event);
	217	cache_error:
	218	exist:
	219	full:
	220	mutex_unlock(&sessions_mutex);
	221	return NULL;
	222	}
	223
	224	/*
	225	* Only used internally at session destruction.
	226	*/
	227	int _ltt_event_unregister(struct ltt_event *event)
	228	{
	229	int ret = -EINVAL;
	230
	231	switch (event->itype) {
	232	case INSTRUM_TRACEPOINTS:
	233	ret = tracepoint_probe_unregister(event->name, event->probe,
	234	event);
	235	if (ret)
	236	return ret;
	237	break;
	238	default:
	239	WARN_ON_ONCE(1);
	240	}
	241	return ret;
	242	}
	243
	244	/*
	245	* Only used internally at session destruction.
	246	*/
	247	void _ltt_event_destroy(struct ltt_event *event)
	248	{
	249	kfree(event->name);
	250	list_del(&event->list);
	251	kmem_cache_free(event_cache, event);
	252	}
	253
	254	/**
	255	* ltt_transport_register - LTT transport registration
	256	* @transport: transport structure
	257	*
	258	* Registers a transport which can be used as output to extract the data out of
	259	* LTTng. The module calling this registration function must ensure that no
	260	* trap-inducing code will be executed by the transport functions. E.g.
	261	* vmalloc_sync_all() must be called between a vmalloc and the moment the memory
	262	* is made visible to the transport function. This registration acts as a
	263	* vmalloc_sync_all. Therefore, only if the module allocates virtual memory
	264	* after its registration must it synchronize the TLBs.
	265	*/
	266	void ltt_transport_register(struct ltt_transport *transport)
	267	{
	268	/*
	269	* Make sure no page fault can be triggered by the module about to be
	270	* registered. We deal with this here so we don't have to call
	271	* vmalloc_sync_all() in each module's init.
	272	*/
	273	vmalloc_sync_all();
	274
	275	mutex_lock(&sessions_mutex);
	276	list_add_tail(&transport->node, &ltt_transport_list);
	277	mutex_unlock(&sessions_mutex);
	278	}
	279	EXPORT_SYMBOL_GPL(ltt_transport_register);
	280
	281	/**
	282	* ltt_transport_unregister - LTT transport unregistration
	283	* @transport: transport structure
	284	*/
	285	void ltt_transport_unregister(struct ltt_transport *transport)
	286	{
	287	mutex_lock(&sessions_mutex);
	288	list_del(&transport->node);
	289	mutex_unlock(&sessions_mutex);
	290	}
	291	EXPORT_SYMBOL_GPL(ltt_transport_unregister);
	292
	293
	294	static int __init ltt_events_init(void)
	295	{
	296	int ret;
	297
	298	event_cache = KMEM_CACHE(ltt_event, 0);
	299	if (!event_cache)
	300	return -ENOMEM;
	301	ret = ltt_probes_init();
	302	if (ret)
	303	goto error;
	304	ret = ltt_debugfs_abi_init();
	305	if (ret)
	306	goto error_abi;
	307	return 0;
	308	error_abi:
	309	ltt_probes_exit();
	310	error:
	311	kmem_cache_destroy(event_cache);
	312	return ret;
	313	}
	314
	315	module_init(ltt_events_init);
	316
	317	static void __exit ltt_events_exit(void)
	318	{
	319	struct ltt_session session, tmpsession;
	320
	321	ltt_debugfs_abi_exit();
	322	ltt_probes_exit();
	323	list_for_each_entry_safe(session, tmpsession, &sessions, list)
	324	ltt_session_destroy(session);
	325	kmem_cache_destroy(event_cache);
	326	}
	327
	328	module_exit(ltt_events_exit);
	329
	330	MODULE_LICENSE("GPL and additional rights");
	331	MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
	332	MODULE_DESCRIPTION("LTTng Events");