ALSA: hda - Add support for Toshiba Satellite M300
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / tracepoint.c
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1 /*
2 * Copyright (C) 2008 Mathieu Desnoyers
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
18 #include <linux/module.h>
19 #include <linux/mutex.h>
20 #include <linux/types.h>
21 #include <linux/jhash.h>
22 #include <linux/list.h>
23 #include <linux/rcupdate.h>
24 #include <linux/tracepoint.h>
25 #include <linux/err.h>
26 #include <linux/slab.h>
27 #include <linux/sched.h>
29 extern struct tracepoint __start___tracepoints[];
30 extern struct tracepoint __stop___tracepoints[];
32 /* Set to 1 to enable tracepoint debug output */
33 static const int tracepoint_debug;
36 * tracepoints_mutex nests inside module_mutex. Tracepoints mutex protects the
37 * builtin and module tracepoints and the hash table.
39 static DEFINE_MUTEX(tracepoints_mutex);
42 * Tracepoint hash table, containing the active tracepoints.
43 * Protected by tracepoints_mutex.
45 #define TRACEPOINT_HASH_BITS 6
46 #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
47 static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
50 * Note about RCU :
51 * It is used to delay the free of multiple probes array until a quiescent
52 * state is reached.
53 * Tracepoint entries modifications are protected by the tracepoints_mutex.
55 struct tracepoint_entry {
56 struct hlist_node hlist;
57 void **funcs;
58 int refcount; /* Number of times armed. 0 if disarmed. */
59 char name[0];
62 struct tp_probes {
63 union {
64 struct rcu_head rcu;
65 struct list_head list;
66 } u;
67 void *probes[0];
70 static inline void *allocate_probes(int count)
72 struct tp_probes *p = kmalloc(count * sizeof(void *)
73 + sizeof(struct tp_probes), GFP_KERNEL);
74 return p == NULL ? NULL : p->probes;
77 static void rcu_free_old_probes(struct rcu_head *head)
79 kfree(container_of(head, struct tp_probes, u.rcu));
82 static inline void release_probes(void *old)
84 if (old) {
85 struct tp_probes *tp_probes = container_of(old,
86 struct tp_probes, probes[0]);
87 call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes);
91 static void debug_print_probes(struct tracepoint_entry *entry)
93 int i;
95 if (!tracepoint_debug || !entry->funcs)
96 return;
98 for (i = 0; entry->funcs[i]; i++)
99 printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i]);
102 static void *
103 tracepoint_entry_add_probe(struct tracepoint_entry *entry, void *probe)
105 int nr_probes = 0;
106 void **old, **new;
108 WARN_ON(!probe);
110 debug_print_probes(entry);
111 old = entry->funcs;
112 if (old) {
113 /* (N -> N+1), (N != 0, 1) probes */
114 for (nr_probes = 0; old[nr_probes]; nr_probes++)
115 if (old[nr_probes] == probe)
116 return ERR_PTR(-EEXIST);
118 /* + 2 : one for new probe, one for NULL func */
119 new = allocate_probes(nr_probes + 2);
120 if (new == NULL)
121 return ERR_PTR(-ENOMEM);
122 if (old)
123 memcpy(new, old, nr_probes * sizeof(void *));
124 new[nr_probes] = probe;
125 new[nr_probes + 1] = NULL;
126 entry->refcount = nr_probes + 1;
127 entry->funcs = new;
128 debug_print_probes(entry);
129 return old;
132 static void *
133 tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe)
135 int nr_probes = 0, nr_del = 0, i;
136 void **old, **new;
138 old = entry->funcs;
140 if (!old)
141 return ERR_PTR(-ENOENT);
143 debug_print_probes(entry);
144 /* (N -> M), (N > 1, M >= 0) probes */
145 for (nr_probes = 0; old[nr_probes]; nr_probes++) {
146 if ((!probe || old[nr_probes] == probe))
147 nr_del++;
150 if (nr_probes - nr_del == 0) {
151 /* N -> 0, (N > 1) */
152 entry->funcs = NULL;
153 entry->refcount = 0;
154 debug_print_probes(entry);
155 return old;
156 } else {
157 int j = 0;
158 /* N -> M, (N > 1, M > 0) */
159 /* + 1 for NULL */
160 new = allocate_probes(nr_probes - nr_del + 1);
161 if (new == NULL)
162 return ERR_PTR(-ENOMEM);
163 for (i = 0; old[i]; i++)
164 if ((probe && old[i] != probe))
165 new[j++] = old[i];
166 new[nr_probes - nr_del] = NULL;
167 entry->refcount = nr_probes - nr_del;
168 entry->funcs = new;
170 debug_print_probes(entry);
171 return old;
175 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
176 * Must be called with tracepoints_mutex held.
177 * Returns NULL if not present.
179 static struct tracepoint_entry *get_tracepoint(const char *name)
181 struct hlist_head *head;
182 struct hlist_node *node;
183 struct tracepoint_entry *e;
184 u32 hash = jhash(name, strlen(name), 0);
186 head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
187 hlist_for_each_entry(e, node, head, hlist) {
188 if (!strcmp(name, e->name))
189 return e;
191 return NULL;
195 * Add the tracepoint to the tracepoint hash table. Must be called with
196 * tracepoints_mutex held.
198 static struct tracepoint_entry *add_tracepoint(const char *name)
200 struct hlist_head *head;
201 struct hlist_node *node;
202 struct tracepoint_entry *e;
203 size_t name_len = strlen(name) + 1;
204 u32 hash = jhash(name, name_len-1, 0);
206 head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
207 hlist_for_each_entry(e, node, head, hlist) {
208 if (!strcmp(name, e->name)) {
209 printk(KERN_NOTICE
210 "tracepoint %s busy\n", name);
211 return ERR_PTR(-EEXIST); /* Already there */
215 * Using kmalloc here to allocate a variable length element. Could
216 * cause some memory fragmentation if overused.
218 e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
219 if (!e)
220 return ERR_PTR(-ENOMEM);
221 memcpy(&e->name[0], name, name_len);
222 e->funcs = NULL;
223 e->refcount = 0;
224 hlist_add_head(&e->hlist, head);
225 return e;
229 * Remove the tracepoint from the tracepoint hash table. Must be called with
230 * mutex_lock held.
232 static inline void remove_tracepoint(struct tracepoint_entry *e)
234 hlist_del(&e->hlist);
235 kfree(e);
239 * Sets the probe callback corresponding to one tracepoint.
241 static void set_tracepoint(struct tracepoint_entry **entry,
242 struct tracepoint *elem, int active)
244 WARN_ON(strcmp((*entry)->name, elem->name) != 0);
246 if (elem->regfunc && !elem->state && active)
247 elem->regfunc();
248 else if (elem->unregfunc && elem->state && !active)
249 elem->unregfunc();
252 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
253 * probe callbacks array is consistent before setting a pointer to it.
254 * This array is referenced by __DO_TRACE from
255 * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
256 * is used.
258 rcu_assign_pointer(elem->funcs, (*entry)->funcs);
259 elem->state = active;
263 * Disable a tracepoint and its probe callback.
264 * Note: only waiting an RCU period after setting elem->call to the empty
265 * function insures that the original callback is not used anymore. This insured
266 * by preempt_disable around the call site.
268 static void disable_tracepoint(struct tracepoint *elem)
270 if (elem->unregfunc && elem->state)
271 elem->unregfunc();
273 elem->state = 0;
274 rcu_assign_pointer(elem->funcs, NULL);
278 * tracepoint_update_probe_range - Update a probe range
279 * @begin: beginning of the range
280 * @end: end of the range
282 * Updates the probe callback corresponding to a range of tracepoints.
284 void
285 tracepoint_update_probe_range(struct tracepoint *begin, struct tracepoint *end)
287 struct tracepoint *iter;
288 struct tracepoint_entry *mark_entry;
290 if (!begin)
291 return;
293 mutex_lock(&tracepoints_mutex);
294 for (iter = begin; iter < end; iter++) {
295 mark_entry = get_tracepoint(iter->name);
296 if (mark_entry) {
297 set_tracepoint(&mark_entry, iter,
298 !!mark_entry->refcount);
299 } else {
300 disable_tracepoint(iter);
303 mutex_unlock(&tracepoints_mutex);
307 * Update probes, removing the faulty probes.
309 static void tracepoint_update_probes(void)
311 /* Core kernel tracepoints */
312 tracepoint_update_probe_range(__start___tracepoints,
313 __stop___tracepoints);
314 /* tracepoints in modules. */
315 module_update_tracepoints();
318 static void *tracepoint_add_probe(const char *name, void *probe)
320 struct tracepoint_entry *entry;
321 void *old;
323 entry = get_tracepoint(name);
324 if (!entry) {
325 entry = add_tracepoint(name);
326 if (IS_ERR(entry))
327 return entry;
329 old = tracepoint_entry_add_probe(entry, probe);
330 if (IS_ERR(old) && !entry->refcount)
331 remove_tracepoint(entry);
332 return old;
336 * tracepoint_probe_register - Connect a probe to a tracepoint
337 * @name: tracepoint name
338 * @probe: probe handler
340 * Returns 0 if ok, error value on error.
341 * The probe address must at least be aligned on the architecture pointer size.
343 int tracepoint_probe_register(const char *name, void *probe)
345 void *old;
347 mutex_lock(&tracepoints_mutex);
348 old = tracepoint_add_probe(name, probe);
349 mutex_unlock(&tracepoints_mutex);
350 if (IS_ERR(old))
351 return PTR_ERR(old);
353 tracepoint_update_probes(); /* may update entry */
354 release_probes(old);
355 return 0;
357 EXPORT_SYMBOL_GPL(tracepoint_probe_register);
359 static void *tracepoint_remove_probe(const char *name, void *probe)
361 struct tracepoint_entry *entry;
362 void *old;
364 entry = get_tracepoint(name);
365 if (!entry)
366 return ERR_PTR(-ENOENT);
367 old = tracepoint_entry_remove_probe(entry, probe);
368 if (IS_ERR(old))
369 return old;
370 if (!entry->refcount)
371 remove_tracepoint(entry);
372 return old;
376 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
377 * @name: tracepoint name
378 * @probe: probe function pointer
380 * We do not need to call a synchronize_sched to make sure the probes have
381 * finished running before doing a module unload, because the module unload
382 * itself uses stop_machine(), which insures that every preempt disabled section
383 * have finished.
385 int tracepoint_probe_unregister(const char *name, void *probe)
387 void *old;
389 mutex_lock(&tracepoints_mutex);
390 old = tracepoint_remove_probe(name, probe);
391 mutex_unlock(&tracepoints_mutex);
392 if (IS_ERR(old))
393 return PTR_ERR(old);
395 tracepoint_update_probes(); /* may update entry */
396 release_probes(old);
397 return 0;
399 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
401 static LIST_HEAD(old_probes);
402 static int need_update;
404 static void tracepoint_add_old_probes(void *old)
406 need_update = 1;
407 if (old) {
408 struct tp_probes *tp_probes = container_of(old,
409 struct tp_probes, probes[0]);
410 list_add(&tp_probes->u.list, &old_probes);
415 * tracepoint_probe_register_noupdate - register a probe but not connect
416 * @name: tracepoint name
417 * @probe: probe handler
419 * caller must call tracepoint_probe_update_all()
421 int tracepoint_probe_register_noupdate(const char *name, void *probe)
423 void *old;
425 mutex_lock(&tracepoints_mutex);
426 old = tracepoint_add_probe(name, probe);
427 if (IS_ERR(old)) {
428 mutex_unlock(&tracepoints_mutex);
429 return PTR_ERR(old);
431 tracepoint_add_old_probes(old);
432 mutex_unlock(&tracepoints_mutex);
433 return 0;
435 EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);
438 * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
439 * @name: tracepoint name
440 * @probe: probe function pointer
442 * caller must call tracepoint_probe_update_all()
444 int tracepoint_probe_unregister_noupdate(const char *name, void *probe)
446 void *old;
448 mutex_lock(&tracepoints_mutex);
449 old = tracepoint_remove_probe(name, probe);
450 if (IS_ERR(old)) {
451 mutex_unlock(&tracepoints_mutex);
452 return PTR_ERR(old);
454 tracepoint_add_old_probes(old);
455 mutex_unlock(&tracepoints_mutex);
456 return 0;
458 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);
461 * tracepoint_probe_update_all - update tracepoints
463 void tracepoint_probe_update_all(void)
465 LIST_HEAD(release_probes);
466 struct tp_probes *pos, *next;
468 mutex_lock(&tracepoints_mutex);
469 if (!need_update) {
470 mutex_unlock(&tracepoints_mutex);
471 return;
473 if (!list_empty(&old_probes))
474 list_replace_init(&old_probes, &release_probes);
475 need_update = 0;
476 mutex_unlock(&tracepoints_mutex);
478 tracepoint_update_probes();
479 list_for_each_entry_safe(pos, next, &release_probes, u.list) {
480 list_del(&pos->u.list);
481 call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);
484 EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);
487 * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
488 * @tracepoint: current tracepoints (in), next tracepoint (out)
489 * @begin: beginning of the range
490 * @end: end of the range
492 * Returns whether a next tracepoint has been found (1) or not (0).
493 * Will return the first tracepoint in the range if the input tracepoint is
494 * NULL.
496 int tracepoint_get_iter_range(struct tracepoint **tracepoint,
497 struct tracepoint *begin, struct tracepoint *end)
499 if (!*tracepoint && begin != end) {
500 *tracepoint = begin;
501 return 1;
503 if (*tracepoint >= begin && *tracepoint < end)
504 return 1;
505 return 0;
507 EXPORT_SYMBOL_GPL(tracepoint_get_iter_range);
509 static void tracepoint_get_iter(struct tracepoint_iter *iter)
511 int found = 0;
513 /* Core kernel tracepoints */
514 if (!iter->module) {
515 found = tracepoint_get_iter_range(&iter->tracepoint,
516 __start___tracepoints, __stop___tracepoints);
517 if (found)
518 goto end;
520 /* tracepoints in modules. */
521 found = module_get_iter_tracepoints(iter);
522 end:
523 if (!found)
524 tracepoint_iter_reset(iter);
527 void tracepoint_iter_start(struct tracepoint_iter *iter)
529 tracepoint_get_iter(iter);
531 EXPORT_SYMBOL_GPL(tracepoint_iter_start);
533 void tracepoint_iter_next(struct tracepoint_iter *iter)
535 iter->tracepoint++;
537 * iter->tracepoint may be invalid because we blindly incremented it.
538 * Make sure it is valid by marshalling on the tracepoints, getting the
539 * tracepoints from following modules if necessary.
541 tracepoint_get_iter(iter);
543 EXPORT_SYMBOL_GPL(tracepoint_iter_next);
545 void tracepoint_iter_stop(struct tracepoint_iter *iter)
548 EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
550 void tracepoint_iter_reset(struct tracepoint_iter *iter)
552 iter->module = NULL;
553 iter->tracepoint = NULL;
555 EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
557 #ifdef CONFIG_MODULES
559 int tracepoint_module_notify(struct notifier_block *self,
560 unsigned long val, void *data)
562 struct module *mod = data;
564 switch (val) {
565 case MODULE_STATE_COMING:
566 case MODULE_STATE_GOING:
567 tracepoint_update_probe_range(mod->tracepoints,
568 mod->tracepoints + mod->num_tracepoints);
569 break;
571 return 0;
574 struct notifier_block tracepoint_module_nb = {
575 .notifier_call = tracepoint_module_notify,
576 .priority = 0,
579 static int init_tracepoints(void)
581 return register_module_notifier(&tracepoint_module_nb);
583 __initcall(init_tracepoints);
585 #endif /* CONFIG_MODULES */
587 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
589 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
590 static int sys_tracepoint_refcount;
592 void syscall_regfunc(void)
594 unsigned long flags;
595 struct task_struct *g, *t;
597 if (!sys_tracepoint_refcount) {
598 read_lock_irqsave(&tasklist_lock, flags);
599 do_each_thread(g, t) {
600 /* Skip kernel threads. */
601 if (t->mm)
602 set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
603 } while_each_thread(g, t);
604 read_unlock_irqrestore(&tasklist_lock, flags);
606 sys_tracepoint_refcount++;
609 void syscall_unregfunc(void)
611 unsigned long flags;
612 struct task_struct *g, *t;
614 sys_tracepoint_refcount--;
615 if (!sys_tracepoint_refcount) {
616 read_lock_irqsave(&tasklist_lock, flags);
617 do_each_thread(g, t) {
618 clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
619 } while_each_thread(g, t);
620 read_unlock_irqrestore(&tasklist_lock, flags);
623 #endif