[lttng-modules.git] / lttng-tracepoint.c

/*
 * lttng-tracepoint.c
 *
 * LTTng adaptation layer for Linux kernel 3.15+ tracepoints.
 *
 * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * 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; only
 * version 2.1 of the License.
 *
 * 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
 */

#include <linux/mutex.h>
#include <linux/err.h>
#include <linux/notifier.h>
#include <linux/tracepoint.h>
#include <linux/slab.h>
#include <linux/jhash.h>
#include <linux/module.h>

#include <lttng-tracepoint.h>
#include <wrapper/list.h>

/*
 * Protect the tracepoint table. lttng_tracepoint_mutex nests within
 * kernel/tracepoint.c tp_modlist_mutex. kernel/tracepoint.c
 * tracepoint_mutex nests within lttng_tracepoint_mutex.
 */
static
DEFINE_MUTEX(lttng_tracepoint_mutex);

#define TRACEPOINT_HASH_BITS 6
#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
static
struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];

/*
 * The tracepoint entry is the node contained within the hash table. It
 * is a mapping from the "string" key to the struct tracepoint pointer.
 */
struct tracepoint_entry {
	struct hlist_node hlist;
	struct tracepoint *tp;
	int refcount;
	struct list_head probes;
	char name[0];
};

struct lttng_tp_probe {
	struct tracepoint_func tp_func;
	struct list_head list;
};

static
int add_probe(struct tracepoint_entry *e, void *probe, void *data)
{
	struct lttng_tp_probe *p;
	int found = 0;

	list_for_each_entry(p, &e->probes, list) {
		if (p->tp_func.func == probe && p->tp_func.data == data) {
			found = 1;
			break;
		}
	}
	if (found)
		return -EEXIST;
	p = kmalloc(sizeof(struct lttng_tp_probe), GFP_KERNEL);
	if (!p)
		return -ENOMEM;
	p->tp_func.func = probe;
	p->tp_func.data = data;
	list_add(&p->list, &e->probes);
	return 0;
}

static
int remove_probe(struct tracepoint_entry *e, void *probe, void *data)
{
	struct lttng_tp_probe *p;
	int found = 0;

	list_for_each_entry(p, &e->probes, list) {
		if (p->tp_func.func == probe && p->tp_func.data == data) {
			found = 1;
			break;
		}
	}
	if (found) {
		list_del(&p->list);
		kfree(p);
		return 0;
	} else {
		WARN_ON(1);
		return -ENOENT;
	}
}

/*
 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
 * Must be called with lttng_tracepoint_mutex held.
 * Returns NULL if not present.
 */
static
struct tracepoint_entry *get_tracepoint(const char *name)
{
	struct hlist_head *head;
	struct tracepoint_entry *e;
	u32 hash = jhash(name, strlen(name), 0);

	head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
	lttng_hlist_for_each_entry(e, head, hlist) {
		if (!strcmp(name, e->name))
			return e;
	}
	return NULL;
}

/*
 * Add the tracepoint to the tracepoint hash table. Must be called with
 * lttng_tracepoint_mutex held.
 */
static
struct tracepoint_entry *add_tracepoint(const char *name)
{
	struct hlist_head *head;
	struct tracepoint_entry *e;
	size_t name_len = strlen(name) + 1;
	u32 hash = jhash(name, name_len - 1, 0);

	head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
	lttng_hlist_for_each_entry(e, head, hlist) {
		if (!strcmp(name, e->name)) {
			printk(KERN_NOTICE
				"tracepoint %s busy\n", name);
			return ERR_PTR(-EEXIST);        /* Already there */
		}
	}
	/*
	 * Using kmalloc here to allocate a variable length element. Could
	 * cause some memory fragmentation if overused.
	 */
	e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
	if (!e)
		return ERR_PTR(-ENOMEM);
	memcpy(&e->name[0], name, name_len);
	e->tp = NULL;
	e->refcount = 0;
	INIT_LIST_HEAD(&e->probes);
	hlist_add_head(&e->hlist, head);
	return e;
}

/*
 * Remove the tracepoint from the tracepoint hash table. Must be called
 * with lttng_tracepoint_mutex held.
 */
static
void remove_tracepoint(struct tracepoint_entry *e)
{
	hlist_del(&e->hlist);
	kfree(e);
}

int lttng_tracepoint_probe_register(const char *name, void *probe, void *data)
{
	struct tracepoint_entry *e;
	int ret = 0;

	mutex_lock(&lttng_tracepoint_mutex);
	e = get_tracepoint(name);
	if (!e) {
		e = add_tracepoint(name);
		if (IS_ERR(e)) {
			ret = PTR_ERR(e);
			goto end;
		}
	}
	/* add (probe, data) to entry */
	ret = add_probe(e, probe, data);
	if (ret)
		goto end;
	e->refcount++;
	if (e->tp) {
		ret = tracepoint_probe_register(e->tp, probe, data);
		WARN_ON_ONCE(ret);
		ret = 0;
	}
end:
	mutex_unlock(&lttng_tracepoint_mutex);
	return ret;
}

int lttng_tracepoint_probe_unregister(const char *name, void *probe, void *data)
{
	struct tracepoint_entry *e;
	int ret = 0;

	mutex_lock(&lttng_tracepoint_mutex);
	e = get_tracepoint(name);
	if (!e) {
		ret = -ENOENT;
		goto end;
	}
	/* remove (probe, data) from entry */
	ret = remove_probe(e, probe, data);
	if (ret)
		goto end;
	if (e->tp) {
		ret = tracepoint_probe_unregister(e->tp, probe, data);
		WARN_ON_ONCE(ret);
		ret = 0;
	}
	if (!--e->refcount)
		remove_tracepoint(e);
end:
	mutex_unlock(&lttng_tracepoint_mutex);
	return ret;
}

#ifdef CONFIG_MODULES

static
int lttng_tracepoint_coming(struct tp_module *tp_mod)
{
	int i;

	mutex_lock(&lttng_tracepoint_mutex);
	for (i = 0; i < tp_mod->mod->num_tracepoints; i++) {
		struct tracepoint *tp;
		struct tracepoint_entry *e;
		struct lttng_tp_probe *p;

		tp = tp_mod->mod->tracepoints_ptrs[i];
		e = get_tracepoint(tp->name);
		if (!e) {
			e = add_tracepoint(tp->name);
			if (IS_ERR(e)) {
				pr_warn("LTTng: error (%ld) adding tracepoint\n",
					PTR_ERR(e));
				continue;
			}
		}
		/* If already enabled, just check consistency */
		if (e->tp) {
			WARN_ON(e->tp != tp);
			continue;
		}
		e->tp = tp;
		e->refcount++;
		/* register each (probe, data) */
		list_for_each_entry(p, &e->probes, list) {
			int ret;

			ret = tracepoint_probe_register(e->tp,
					p->tp_func.func, p->tp_func.data);
			WARN_ON_ONCE(ret);
		}
	}
	mutex_unlock(&lttng_tracepoint_mutex);
	return 0;
}

static
int lttng_tracepoint_going(struct tp_module *tp_mod)
{
	int i;

	mutex_lock(&lttng_tracepoint_mutex);
	for (i = 0; i < tp_mod->mod->num_tracepoints; i++) {
		struct tracepoint *tp;
		struct tracepoint_entry *e;
		struct lttng_tp_probe *p;

		tp = tp_mod->mod->tracepoints_ptrs[i];
		e = get_tracepoint(tp->name);
		if (!e || !e->tp)
			continue;
		/* unregister each (probe, data) */
		list_for_each_entry(p, &e->probes, list) {
			int ret;

			ret = tracepoint_probe_unregister(e->tp,
					p->tp_func.func, p->tp_func.data);
			WARN_ON_ONCE(ret);
		}
		e->tp = NULL;
		if (!--e->refcount)
			remove_tracepoint(e);
	}
	mutex_unlock(&lttng_tracepoint_mutex);
	return 0;
}

static
int lttng_tracepoint_notify(struct notifier_block *self,
		unsigned long val, void *data)
{
	struct tp_module *tp_mod = data;
	int ret = 0;

	switch (val) {
	case MODULE_STATE_COMING:
		ret = lttng_tracepoint_coming(tp_mod);
		break;
	case MODULE_STATE_GOING:
		ret = lttng_tracepoint_going(tp_mod);
		break;
	default:
		break;
	}
	return ret;
}

static
struct notifier_block lttng_tracepoint_notifier = {
	.notifier_call = lttng_tracepoint_notify,
	.priority = 0,
};

static
int lttng_tracepoint_module_init(void)
{
	return register_tracepoint_module_notifier(&lttng_tracepoint_notifier);
}

static
void lttng_tracepoint_module_exit(void)
{
	WARN_ON(unregister_tracepoint_module_notifier(&lttng_tracepoint_notifier));
}

#else /* #ifdef CONFIG_MODULES */

static
int lttng_tracepoint_module_init(void)
{
	return 0;
}

static
void lttng_tracepoint_module_exit(void)
{
}

#endif /* #else #ifdef CONFIG_MODULES */

static
void lttng_kernel_tracepoint_add(struct tracepoint *tp, void *priv)
{
	struct tracepoint_entry *e;
	struct lttng_tp_probe *p;
	int *ret = priv;

	mutex_lock(&lttng_tracepoint_mutex);
	e = get_tracepoint(tp->name);
	if (!e) {
		e = add_tracepoint(tp->name);
		if (IS_ERR(e)) {
			pr_warn("LTTng: error (%ld) adding tracepoint\n",
				PTR_ERR(e));
			*ret = (int) PTR_ERR(e);
			goto end;
		}
	}
	/* If already enabled, just check consistency */
	if (e->tp) {
		WARN_ON(e->tp != tp);
		goto end;
	}
	e->tp = tp;
	e->refcount++;
	/* register each (probe, data) */
	list_for_each_entry(p, &e->probes, list) {
		int ret;

		ret = tracepoint_probe_register(e->tp,
				p->tp_func.func, p->tp_func.data);
		WARN_ON_ONCE(ret);
	}
end:
	mutex_unlock(&lttng_tracepoint_mutex);
}

static
void lttng_kernel_tracepoint_remove(struct tracepoint *tp, void *priv)
{
	struct tracepoint_entry *e;
	int *ret = priv;

	mutex_lock(&lttng_tracepoint_mutex);
	e = get_tracepoint(tp->name);
	if (!e || e->refcount != 1 || !list_empty(&e->probes)) {
		*ret = -EINVAL;
		goto end;
	}
	remove_tracepoint(e);
end:
	mutex_unlock(&lttng_tracepoint_mutex);
}

int __init lttng_tracepoint_init(void)
{
	int ret = 0;

	for_each_kernel_tracepoint(lttng_kernel_tracepoint_add, &ret);
	if (ret)
		goto error;
	ret = lttng_tracepoint_module_init();
	if (ret)
		goto error_module;
	return 0;

error_module:
	{
		int error_ret = 0;

		for_each_kernel_tracepoint(lttng_kernel_tracepoint_remove,
				&error_ret);
		WARN_ON(error_ret);
	}
error:
	return ret;
}

void lttng_tracepoint_exit(void)
{
	int i, ret = 0;

	lttng_tracepoint_module_exit();
	for_each_kernel_tracepoint(lttng_kernel_tracepoint_remove, &ret);
	WARN_ON(ret);
	mutex_lock(&lttng_tracepoint_mutex);
	for (i = 0; i < TRACEPOINT_TABLE_SIZE; i++) {
		struct hlist_head *head = &tracepoint_table[i];

		/* All tracepoints should be removed */
		WARN_ON(!hlist_empty(head));
	}
	mutex_unlock(&lttng_tracepoint_mutex);
}
Commit	Line	Data
20591cf7 MD	1	/*
	2	* lttng-tracepoint.c
	3	*
	4	* LTTng adaptation layer for Linux kernel 3.15+ tracepoints.
	5	*
	6	* Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	7	*
	8	* This library is free software; you can redistribute it and/or
	9	* modify it under the terms of the GNU Lesser General Public
	10	* License as published by the Free Software Foundation; only
	11	* version 2.1 of the License.
	12	*
	13	* This library is distributed in the hope that it will be useful,
	14	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	15	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	16	* Lesser General Public License for more details.
	17	*
	18	* You should have received a copy of the GNU Lesser General Public
	19	* License along with this library; if not, write to the Free Software
	20	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	21	*/
	22
20591cf7 MD	23	#include <linux/mutex.h>
	24	#include <linux/err.h>
	25	#include <linux/notifier.h>
	26	#include <linux/tracepoint.h>
	27	#include <linux/slab.h>
	28	#include <linux/jhash.h>
	29	#include <linux/module.h>
	30
241ae9a8 MD	31	#include <lttng-tracepoint.h>
241ae9a8 MD	32	#include <wrapper/list.h>
20591cf7 MD	33
	34	/*
	35	* Protect the tracepoint table. lttng_tracepoint_mutex nests within
	36	* kernel/tracepoint.c tp_modlist_mutex. kernel/tracepoint.c
	37	* tracepoint_mutex nests within lttng_tracepoint_mutex.
	38	*/
	39	static
	40	DEFINE_MUTEX(lttng_tracepoint_mutex);
	41
	42	#define TRACEPOINT_HASH_BITS 6
	43	#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
	44	static
	45	struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
	46
	47	/*
	48	* The tracepoint entry is the node contained within the hash table. It
	49	* is a mapping from the "string" key to the struct tracepoint pointer.
	50	*/
	51	struct tracepoint_entry {
	52	struct hlist_node hlist;
	53	struct tracepoint *tp;
	54	int refcount;
	55	struct list_head probes;
	56	char name[0];
	57	};
	58
	59	struct lttng_tp_probe {
	60	struct tracepoint_func tp_func;
	61	struct list_head list;
	62	};
	63
	64	static
	65	int add_probe(struct tracepoint_entry e, void probe, void *data)
	66	{
	67	struct lttng_tp_probe *p;
	68	int found = 0;
	69
	70	list_for_each_entry(p, &e->probes, list) {
	71	if (p->tp_func.func == probe && p->tp_func.data == data) {
	72	found = 1;
	73	break;
	74	}
	75	}
	76	if (found)
	77	return -EEXIST;
	78	p = kmalloc(sizeof(struct lttng_tp_probe), GFP_KERNEL);
	79	if (!p)
	80	return -ENOMEM;
	81	p->tp_func.func = probe;
	82	p->tp_func.data = data;
	83	list_add(&p->list, &e->probes);
	84	return 0;
	85	}
	86
	87	static
	88	int remove_probe(struct tracepoint_entry e, void probe, void *data)
	89	{
	90	struct lttng_tp_probe *p;
	91	int found = 0;
	92
	93	list_for_each_entry(p, &e->probes, list) {
	94	if (p->tp_func.func == probe && p->tp_func.data == data) {
	95	found = 1;
	96	break;
97	}
98	}
99	if (found) {
100	list_del(&p->list);
101	kfree(p);
102	return 0;
103	} else {
104	WARN_ON(1);
105	return -ENOENT;
106	}
107	}
108
109	/*
110	* Get tracepoint if the tracepoint is present in the tracepoint hash table.
111	* Must be called with lttng_tracepoint_mutex held.
112	* Returns NULL if not present.
113	*/
114	static
115	struct tracepoint_entry get_tracepoint(const char name)
116	{
117	struct hlist_head *head;
118	struct tracepoint_entry *e;
119	u32 hash = jhash(name, strlen(name), 0);
120
121	head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
f934e302	122	lttng_hlist_for_each_entry(e, head, hlist) {
20591cf7 MD	123	if (!strcmp(name, e->name))
	124	return e;
	125	}
	126	return NULL;
	127	}
	128
	129	/*
	130	* Add the tracepoint to the tracepoint hash table. Must be called with
	131	* lttng_tracepoint_mutex held.
	132	*/
	133	static
	134	struct tracepoint_entry add_tracepoint(const char name)
	135	{
	136	struct hlist_head *head;
	137	struct tracepoint_entry *e;
	138	size_t name_len = strlen(name) + 1;
	139	u32 hash = jhash(name, name_len - 1, 0);
	140
	141	head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
f934e302	142	lttng_hlist_for_each_entry(e, head, hlist) {
20591cf7 MD	143	if (!strcmp(name, e->name)) {
	144	printk(KERN_NOTICE
	145	"tracepoint %s busy\n", name);
	146	return ERR_PTR(-EEXIST); /* Already there */
	147	}
	148	}
	149	/*
	150	* Using kmalloc here to allocate a variable length element. Could
	151	* cause some memory fragmentation if overused.
	152	*/
	153	e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
	154	if (!e)
	155	return ERR_PTR(-ENOMEM);
	156	memcpy(&e->name[0], name, name_len);
	157	e->tp = NULL;
	158	e->refcount = 0;
	159	INIT_LIST_HEAD(&e->probes);
	160	hlist_add_head(&e->hlist, head);
	161	return e;
	162	}
	163
	164	/*
	165	* Remove the tracepoint from the tracepoint hash table. Must be called
	166	* with lttng_tracepoint_mutex held.
	167	*/
	168	static
	169	void remove_tracepoint(struct tracepoint_entry *e)
	170	{
	171	hlist_del(&e->hlist);
	172	kfree(e);
	173	}
	174
	175	int lttng_tracepoint_probe_register(const char name, void probe, void *data)
	176	{
	177	struct tracepoint_entry *e;
	178	int ret = 0;
	179
	180	mutex_lock(&lttng_tracepoint_mutex);
	181	e = get_tracepoint(name);
	182	if (!e) {
	183	e = add_tracepoint(name);
	184	if (IS_ERR(e)) {
	185	ret = PTR_ERR(e);
	186	goto end;
	187	}
	188	}
	189	/* add (probe, data) to entry */
	190	ret = add_probe(e, probe, data);
	191	if (ret)
	192	goto end;
	193	e->refcount++;
	194	if (e->tp) {
	195	ret = tracepoint_probe_register(e->tp, probe, data);
	196	WARN_ON_ONCE(ret);
	197	ret = 0;
	198	}
	199	end:
	200	mutex_unlock(&lttng_tracepoint_mutex);
	201	return ret;
	202	}
	203
	204	int lttng_tracepoint_probe_unregister(const char name, void probe, void *data)
	205	{
	206	struct tracepoint_entry *e;
207	int ret = 0;
208
209	mutex_lock(&lttng_tracepoint_mutex);
210	e = get_tracepoint(name);
211	if (!e) {
212	ret = -ENOENT;
213	goto end;
214	}
215	/* remove (probe, data) from entry */
216	ret = remove_probe(e, probe, data);
217	if (ret)
218	goto end;
219	if (e->tp) {
220	ret = tracepoint_probe_unregister(e->tp, probe, data);
221	WARN_ON_ONCE(ret);
222	ret = 0;
223	}
224	if (!--e->refcount)
225	remove_tracepoint(e);
226	end:
227	mutex_unlock(&lttng_tracepoint_mutex);
228	return ret;
229	}
230
231	#ifdef CONFIG_MODULES
232
233	static
234	int lttng_tracepoint_coming(struct tp_module *tp_mod)
235	{
236	int i;
237
238	mutex_lock(&lttng_tracepoint_mutex);
239	for (i = 0; i < tp_mod->mod->num_tracepoints; i++) {
240	struct tracepoint *tp;
241	struct tracepoint_entry *e;
242	struct lttng_tp_probe *p;
243
244	tp = tp_mod->mod->tracepoints_ptrs[i];
245	e = get_tracepoint(tp->name);
246	if (!e) {
247	e = add_tracepoint(tp->name);
248	if (IS_ERR(e)) {
249	pr_warn("LTTng: error (%ld) adding tracepoint\n",
250	PTR_ERR(e));
251	continue;
252	}
253	}
254	/* If already enabled, just check consistency */
255	if (e->tp) {
256	WARN_ON(e->tp != tp);
257	continue;
258	}
259	e->tp = tp;
260	e->refcount++;
261	/* register each (probe, data) */
262	list_for_each_entry(p, &e->probes, list) {
263	int ret;
264
265	ret = tracepoint_probe_register(e->tp,
266	p->tp_func.func, p->tp_func.data);
267	WARN_ON_ONCE(ret);
268	}
269	}
270	mutex_unlock(&lttng_tracepoint_mutex);
271	return 0;
272	}
273
274	static
275	int lttng_tracepoint_going(struct tp_module *tp_mod)
276	{
277	int i;
278
279	mutex_lock(&lttng_tracepoint_mutex);
280	for (i = 0; i < tp_mod->mod->num_tracepoints; i++) {
281	struct tracepoint *tp;
282	struct tracepoint_entry *e;
283	struct lttng_tp_probe *p;
284
285	tp = tp_mod->mod->tracepoints_ptrs[i];
286	e = get_tracepoint(tp->name);
287	if (!e \|\| !e->tp)
288	continue;
289	/* unregister each (probe, data) */
290	list_for_each_entry(p, &e->probes, list) {
291	int ret;
292
293	ret = tracepoint_probe_unregister(e->tp,
294	p->tp_func.func, p->tp_func.data);
295	WARN_ON_ONCE(ret);
296	}
297	e->tp = NULL;
298	if (!--e->refcount)
299	remove_tracepoint(e);
300	}
301	mutex_unlock(&lttng_tracepoint_mutex);
302	return 0;
303	}
304
305	static
306	int lttng_tracepoint_notify(struct notifier_block *self,
307	unsigned long val, void *data)
308	{
309	struct tp_module *tp_mod = data;
310	int ret = 0;
311
312	switch (val) {
313	case MODULE_STATE_COMING:
314	ret = lttng_tracepoint_coming(tp_mod);
315	break;
316	case MODULE_STATE_GOING:
317	ret = lttng_tracepoint_going(tp_mod);
318	break;
319	default:
320	break;
321	}
322	return ret;
323	}
324
325	static
326	struct notifier_block lttng_tracepoint_notifier = {
327	.notifier_call = lttng_tracepoint_notify,
328	.priority = 0,
329	};
330
331	static
332	int lttng_tracepoint_module_init(void)
333	{
334	return register_tracepoint_module_notifier(&lttng_tracepoint_notifier);
335	}
336
337	static
338	void lttng_tracepoint_module_exit(void)
339	{
340	WARN_ON(unregister_tracepoint_module_notifier(&lttng_tracepoint_notifier));
341	}
342
343	#else /* #ifdef CONFIG_MODULES */
344
345	static
346	int lttng_tracepoint_module_init(void)
347	{
348	return 0;
349	}
350
351	static
352	void lttng_tracepoint_module_exit(void)
353	{
354	}
355
356	#endif /* #else #ifdef CONFIG_MODULES */
357
358	static
359	void lttng_kernel_tracepoint_add(struct tracepoint tp, void priv)
360	{
361	struct tracepoint_entry *e;
362	struct lttng_tp_probe *p;
363	int *ret = priv;
364
365	mutex_lock(&lttng_tracepoint_mutex);
366	e = get_tracepoint(tp->name);
367	if (!e) {
368	e = add_tracepoint(tp->name);
369	if (IS_ERR(e)) {
370	pr_warn("LTTng: error (%ld) adding tracepoint\n",
371	PTR_ERR(e));
372	*ret = (int) PTR_ERR(e);
373	goto end;
374	}
375	}
376	/* If already enabled, just check consistency */
377	if (e->tp) {
378	WARN_ON(e->tp != tp);
379	goto end;
380	}
381	e->tp = tp;
382	e->refcount++;
383	/* register each (probe, data) */
384	list_for_each_entry(p, &e->probes, list) {
385	int ret;
386
387	ret = tracepoint_probe_register(e->tp,
388	p->tp_func.func, p->tp_func.data);
389	WARN_ON_ONCE(ret);
390	}
391	end:
392	mutex_unlock(&lttng_tracepoint_mutex);
393	}
394
395	static
396	void lttng_kernel_tracepoint_remove(struct tracepoint tp, void priv)
397	{
398	struct tracepoint_entry *e;
399	int *ret = priv;
400
401	mutex_lock(&lttng_tracepoint_mutex);
402	e = get_tracepoint(tp->name);
403	if (!e \|\| e->refcount != 1 \|\| !list_empty(&e->probes)) {
404	*ret = -EINVAL;
405	goto end;
406	}
407	remove_tracepoint(e);
408	end:
409	mutex_unlock(&lttng_tracepoint_mutex);
410	}
411
412	int __init lttng_tracepoint_init(void)
413	{
414	int ret = 0;
415
416	for_each_kernel_tracepoint(lttng_kernel_tracepoint_add, &ret);
417	if (ret)
418	goto error;
419	ret = lttng_tracepoint_module_init();
420	if (ret)
421	goto error_module;
422	return 0;
423
424	error_module:
425	{
426	int error_ret = 0;
427
428	for_each_kernel_tracepoint(lttng_kernel_tracepoint_remove,
429	&error_ret);
430	WARN_ON(error_ret);
431	}
432	error:
433	return ret;
434	}
435
436	void lttng_tracepoint_exit(void)
437	{
438	int i, ret = 0;
439
440	lttng_tracepoint_module_exit();
441	for_each_kernel_tracepoint(lttng_kernel_tracepoint_remove, &ret);
442	WARN_ON(ret);
443	mutex_lock(&lttng_tracepoint_mutex);
444	for (i = 0; i < TRACEPOINT_TABLE_SIZE; i++) {
445	struct hlist_head *head = &tracepoint_table[i];
446
447	/* All tracepoints should be removed */
448	WARN_ON(!hlist_empty(head));
449	}
450	mutex_unlock(&lttng_tracepoint_mutex);
451	}