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Commit 127cafbb authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Ingo Molnar
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tracepoint: introduce *_noupdate APIs. 



Impact: add new tracepoint APIs to allow the batched registration of probes

new APIs separate tracepoint_probe_register(),
tracepoint_probe_unregister() into 2 steps. The first step of them
is just update tracepoint_entry, not connect or disconnect.

this patch introduces tracepoint_probe_update_all() for update all.

these APIs are very useful for registering lots of probes
but just updating once. Another very important thing is that
*_noupdate APIs do not require module_mutex.

Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: default avatarMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 19dba33c

include/linux/tracepoint.h

+4 −0
Original line number Diff line number Diff line
@@ -112,6 +112,10 @@ extern int tracepoint_probe_register(const char *name, void *probe); 
 */

extern int tracepoint_probe_unregister(const char *name, void *probe);



extern int tracepoint_probe_register_noupdate(const char *name, void *probe);

extern int tracepoint_probe_unregister_noupdate(const char *name, void *probe);

extern void tracepoint_probe_update_all(void);



struct tracepoint_iter {

	struct module *module;

	struct tracepoint *tracepoint;

kernel/tracepoint.c

+132 −38
Original line number Diff line number Diff line
@@ -59,7 +59,10 @@ struct tracepoint_entry { 
};



struct tp_probes {

	union {

		struct rcu_head rcu;

		struct list_head list;

	} u;

	void *probes[0];

};
@@ -72,7 +75,7 @@ static inline void *allocate_probes(int count) 


static void rcu_free_old_probes(struct rcu_head *head)

{

	kfree(container_of(head, struct tp_probes, rcu));

	kfree(container_of(head, struct tp_probes, u.rcu));

}



static inline void release_probes(void *old)
@@ -80,7 +83,7 @@ static inline void release_probes(void *old) 
	if (old) {

		struct tp_probes *tp_probes = container_of(old,

			struct tp_probes, probes[0]);

		call_rcu(&tp_probes->rcu, rcu_free_old_probes);

		call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes);

	}

}
@@ -299,6 +302,23 @@ static void tracepoint_update_probes(void) 
	module_update_tracepoints();

}



static void *tracepoint_add_probe(const char *name, void *probe)

{

	struct tracepoint_entry *entry;

	void *old;



	entry = get_tracepoint(name);

	if (!entry) {

		entry = add_tracepoint(name);

		if (IS_ERR(entry))

			return entry;

	}

	old = tracepoint_entry_add_probe(entry, probe);

	if (IS_ERR(old) && !entry->refcount)

		remove_tracepoint(entry);

	return old;

}



/**

 * tracepoint_probe_register -  Connect a probe to a tracepoint

 * @name: tracepoint name
@@ -309,36 +329,36 @@ static void tracepoint_update_probes(void) 
 */

int tracepoint_probe_register(const char *name, void *probe)

{

	struct tracepoint_entry *entry;

	int ret = 0;

	void *old;



	mutex_lock(&tracepoints_mutex);

	entry = get_tracepoint(name);

	if (!entry) {

		entry = add_tracepoint(name);

		if (IS_ERR(entry)) {

			ret = PTR_ERR(entry);

			goto end;

		}

	}

	old = tracepoint_entry_add_probe(entry, probe);

	if (IS_ERR(old)) {

		if (!entry->refcount)

			remove_tracepoint(entry);

		ret = PTR_ERR(old);

		goto end;

	}

	old = tracepoint_add_probe(name, probe);

	mutex_unlock(&tracepoints_mutex);

	if (IS_ERR(old))

		return PTR_ERR(old);



	tracepoint_update_probes();		/* may update entry */

	release_probes(old);

	return 0;

end:

	mutex_unlock(&tracepoints_mutex);

	return ret;

}

EXPORT_SYMBOL_GPL(tracepoint_probe_register);



static void *tracepoint_remove_probe(const char *name, void *probe)

{

	struct tracepoint_entry *entry;

	void *old;



	entry = get_tracepoint(name);

	if (!entry)

		return ERR_PTR(-ENOENT);

	old = tracepoint_entry_remove_probe(entry, probe);

	if (IS_ERR(old))

		return old;

	if (!entry->refcount)

		remove_tracepoint(entry);

	return old;

}



/**

 * tracepoint_probe_unregister -  Disconnect a probe from a tracepoint

 * @name: tracepoint name
@@ -351,31 +371,105 @@ EXPORT_SYMBOL_GPL(tracepoint_probe_register); 
 */

int tracepoint_probe_unregister(const char *name, void *probe)

{

	struct tracepoint_entry *entry;

	void *old;

	int ret = -ENOENT;



	mutex_lock(&tracepoints_mutex);

	entry = get_tracepoint(name);

	if (!entry)

		goto end;

	old = tracepoint_entry_remove_probe(entry, probe);

	if (IS_ERR(old)) {

		ret = PTR_ERR(old);

		goto end;

	}

	if (!entry->refcount)

		remove_tracepoint(entry);

	old = tracepoint_remove_probe(name, probe);

	mutex_unlock(&tracepoints_mutex);

	if (IS_ERR(old))

		return PTR_ERR(old);



	tracepoint_update_probes();		/* may update entry */

	release_probes(old);

	return 0;

end:

	mutex_unlock(&tracepoints_mutex);

	return ret;

}

EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);



static LIST_HEAD(old_probes);

static int need_update;



static void tracepoint_add_old_probes(void *old)

{

	need_update = 1;

	if (old) {

		struct tp_probes *tp_probes = container_of(old,

			struct tp_probes, probes[0]);

		list_add(&tp_probes->u.list, &old_probes);

	}

}



/**

 * tracepoint_probe_register_noupdate -  register a probe but not connect

 * @name: tracepoint name

 * @probe: probe handler

 *

 * caller must call tracepoint_probe_update_all()

 */

int tracepoint_probe_register_noupdate(const char *name, void *probe)

{

	void *old;



	mutex_lock(&tracepoints_mutex);

	old = tracepoint_add_probe(name, probe);

	if (IS_ERR(old)) {

		mutex_unlock(&tracepoints_mutex);

		return PTR_ERR(old);

	}

	tracepoint_add_old_probes(old);

	mutex_unlock(&tracepoints_mutex);

	return 0;

}

EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);



/**

 * tracepoint_probe_unregister_noupdate -  remove a probe but not disconnect

 * @name: tracepoint name

 * @probe: probe function pointer

 *

 * caller must call tracepoint_probe_update_all()

 */

int tracepoint_probe_unregister_noupdate(const char *name, void *probe)

{

	void *old;



	mutex_lock(&tracepoints_mutex);

	old = tracepoint_remove_probe(name, probe);

	if (IS_ERR(old)) {

		mutex_unlock(&tracepoints_mutex);

		return PTR_ERR(old);

	}

	tracepoint_add_old_probes(old);

	mutex_unlock(&tracepoints_mutex);

	return 0;

}

EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);



/**

 * tracepoint_probe_update_all -  update tracepoints

 */

void tracepoint_probe_update_all(void)

{

	LIST_HEAD(release_probes);

	struct tp_probes *pos, *next;



	mutex_lock(&tracepoints_mutex);

	if (!need_update) {

		mutex_unlock(&tracepoints_mutex);

		return;

	}

	if (!list_empty(&old_probes))

		list_replace_init(&old_probes, &release_probes);

	need_update = 0;

	mutex_unlock(&tracepoints_mutex);



	tracepoint_update_probes();

	list_for_each_entry_safe(pos, next, &release_probes, u.list) {

		list_del(&pos->u.list);

		call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);

	}

}

EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);



/**

 * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.

 * @tracepoint: current tracepoints (in), next tracepoint (out)