btrfs: rename the option to nospace_cache
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / tracepoint.c
blobb219f1449c54f5a93cd83d8f22387b4ae1fe498f
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>
28 #include <linux/jump_label.h>
30 extern struct tracepoint * const __start___tracepoints_ptrs[];
31 extern struct tracepoint * const __stop___tracepoints_ptrs[];
33 /* Set to 1 to enable tracepoint debug output */
34 static const int tracepoint_debug;
37 * tracepoints_mutex nests inside module_mutex. Tracepoints mutex protects the
38 * builtin and module tracepoints and the hash table.
40 static DEFINE_MUTEX(tracepoints_mutex);
43 * Tracepoint hash table, containing the active tracepoints.
44 * Protected by tracepoints_mutex.
46 #define TRACEPOINT_HASH_BITS 6
47 #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
48 static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
51 * Note about RCU :
52 * It is used to delay the free of multiple probes array until a quiescent
53 * state is reached.
54 * Tracepoint entries modifications are protected by the tracepoints_mutex.
56 struct tracepoint_entry {
57 struct hlist_node hlist;
58 struct tracepoint_func *funcs;
59 int refcount; /* Number of times armed. 0 if disarmed. */
60 char name[0];
63 struct tp_probes {
64 union {
65 struct rcu_head rcu;
66 struct list_head list;
67 } u;
68 struct tracepoint_func probes[0];
71 static inline void *allocate_probes(int count)
73 struct tp_probes *p = kmalloc(count * sizeof(struct tracepoint_func)
74 + sizeof(struct tp_probes), GFP_KERNEL);
75 return p == NULL ? NULL : p->probes;
78 static void rcu_free_old_probes(struct rcu_head *head)
80 kfree(container_of(head, struct tp_probes, u.rcu));
83 static inline void release_probes(struct tracepoint_func *old)
85 if (old) {
86 struct tp_probes *tp_probes = container_of(old,
87 struct tp_probes, probes[0]);
88 call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes);
92 static void debug_print_probes(struct tracepoint_entry *entry)
94 int i;
96 if (!tracepoint_debug || !entry->funcs)
97 return;
99 for (i = 0; entry->funcs[i].func; i++)
100 printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i].func);
103 static struct tracepoint_func *
104 tracepoint_entry_add_probe(struct tracepoint_entry *entry,
105 void *probe, void *data)
107 int nr_probes = 0;
108 struct tracepoint_func *old, *new;
110 WARN_ON(!probe);
112 debug_print_probes(entry);
113 old = entry->funcs;
114 if (old) {
115 /* (N -> N+1), (N != 0, 1) probes */
116 for (nr_probes = 0; old[nr_probes].func; nr_probes++)
117 if (old[nr_probes].func == probe &&
118 old[nr_probes].data == data)
119 return ERR_PTR(-EEXIST);
121 /* + 2 : one for new probe, one for NULL func */
122 new = allocate_probes(nr_probes + 2);
123 if (new == NULL)
124 return ERR_PTR(-ENOMEM);
125 if (old)
126 memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
127 new[nr_probes].func = probe;
128 new[nr_probes].data = data;
129 new[nr_probes + 1].func = NULL;
130 entry->refcount = nr_probes + 1;
131 entry->funcs = new;
132 debug_print_probes(entry);
133 return old;
136 static void *
137 tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
138 void *probe, void *data)
140 int nr_probes = 0, nr_del = 0, i;
141 struct tracepoint_func *old, *new;
143 old = entry->funcs;
145 if (!old)
146 return ERR_PTR(-ENOENT);
148 debug_print_probes(entry);
149 /* (N -> M), (N > 1, M >= 0) probes */
150 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
151 if (!probe ||
152 (old[nr_probes].func == probe &&
153 old[nr_probes].data == data))
154 nr_del++;
157 if (nr_probes - nr_del == 0) {
158 /* N -> 0, (N > 1) */
159 entry->funcs = NULL;
160 entry->refcount = 0;
161 debug_print_probes(entry);
162 return old;
163 } else {
164 int j = 0;
165 /* N -> M, (N > 1, M > 0) */
166 /* + 1 for NULL */
167 new = allocate_probes(nr_probes - nr_del + 1);
168 if (new == NULL)
169 return ERR_PTR(-ENOMEM);
170 for (i = 0; old[i].func; i++)
171 if (probe &&
172 (old[i].func != probe || old[i].data != data))
173 new[j++] = old[i];
174 new[nr_probes - nr_del].func = NULL;
175 entry->refcount = nr_probes - nr_del;
176 entry->funcs = new;
178 debug_print_probes(entry);
179 return old;
183 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
184 * Must be called with tracepoints_mutex held.
185 * Returns NULL if not present.
187 static struct tracepoint_entry *get_tracepoint(const char *name)
189 struct hlist_head *head;
190 struct hlist_node *node;
191 struct tracepoint_entry *e;
192 u32 hash = jhash(name, strlen(name), 0);
194 head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
195 hlist_for_each_entry(e, node, head, hlist) {
196 if (!strcmp(name, e->name))
197 return e;
199 return NULL;
203 * Add the tracepoint to the tracepoint hash table. Must be called with
204 * tracepoints_mutex held.
206 static struct tracepoint_entry *add_tracepoint(const char *name)
208 struct hlist_head *head;
209 struct hlist_node *node;
210 struct tracepoint_entry *e;
211 size_t name_len = strlen(name) + 1;
212 u32 hash = jhash(name, name_len-1, 0);
214 head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
215 hlist_for_each_entry(e, node, head, hlist) {
216 if (!strcmp(name, e->name)) {
217 printk(KERN_NOTICE
218 "tracepoint %s busy\n", name);
219 return ERR_PTR(-EEXIST); /* Already there */
223 * Using kmalloc here to allocate a variable length element. Could
224 * cause some memory fragmentation if overused.
226 e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
227 if (!e)
228 return ERR_PTR(-ENOMEM);
229 memcpy(&e->name[0], name, name_len);
230 e->funcs = NULL;
231 e->refcount = 0;
232 hlist_add_head(&e->hlist, head);
233 return e;
237 * Remove the tracepoint from the tracepoint hash table. Must be called with
238 * mutex_lock held.
240 static inline void remove_tracepoint(struct tracepoint_entry *e)
242 hlist_del(&e->hlist);
243 kfree(e);
247 * Sets the probe callback corresponding to one tracepoint.
249 static void set_tracepoint(struct tracepoint_entry **entry,
250 struct tracepoint *elem, int active)
252 WARN_ON(strcmp((*entry)->name, elem->name) != 0);
254 if (elem->regfunc && !jump_label_enabled(&elem->key) && active)
255 elem->regfunc();
256 else if (elem->unregfunc && jump_label_enabled(&elem->key) && !active)
257 elem->unregfunc();
260 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
261 * probe callbacks array is consistent before setting a pointer to it.
262 * This array is referenced by __DO_TRACE from
263 * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
264 * is used.
266 rcu_assign_pointer(elem->funcs, (*entry)->funcs);
267 if (active && !jump_label_enabled(&elem->key))
268 jump_label_inc(&elem->key);
269 else if (!active && jump_label_enabled(&elem->key))
270 jump_label_dec(&elem->key);
274 * Disable a tracepoint and its probe callback.
275 * Note: only waiting an RCU period after setting elem->call to the empty
276 * function insures that the original callback is not used anymore. This insured
277 * by preempt_disable around the call site.
279 static void disable_tracepoint(struct tracepoint *elem)
281 if (elem->unregfunc && jump_label_enabled(&elem->key))
282 elem->unregfunc();
284 if (jump_label_enabled(&elem->key))
285 jump_label_dec(&elem->key);
286 rcu_assign_pointer(elem->funcs, NULL);
290 * tracepoint_update_probe_range - Update a probe range
291 * @begin: beginning of the range
292 * @end: end of the range
294 * Updates the probe callback corresponding to a range of tracepoints.
296 void tracepoint_update_probe_range(struct tracepoint * const *begin,
297 struct tracepoint * const *end)
299 struct tracepoint * const *iter;
300 struct tracepoint_entry *mark_entry;
302 if (!begin)
303 return;
305 mutex_lock(&tracepoints_mutex);
306 for (iter = begin; iter < end; iter++) {
307 mark_entry = get_tracepoint((*iter)->name);
308 if (mark_entry) {
309 set_tracepoint(&mark_entry, *iter,
310 !!mark_entry->refcount);
311 } else {
312 disable_tracepoint(*iter);
315 mutex_unlock(&tracepoints_mutex);
319 * Update probes, removing the faulty probes.
321 static void tracepoint_update_probes(void)
323 /* Core kernel tracepoints */
324 tracepoint_update_probe_range(__start___tracepoints_ptrs,
325 __stop___tracepoints_ptrs);
326 /* tracepoints in modules. */
327 module_update_tracepoints();
330 static struct tracepoint_func *
331 tracepoint_add_probe(const char *name, void *probe, void *data)
333 struct tracepoint_entry *entry;
334 struct tracepoint_func *old;
336 entry = get_tracepoint(name);
337 if (!entry) {
338 entry = add_tracepoint(name);
339 if (IS_ERR(entry))
340 return (struct tracepoint_func *)entry;
342 old = tracepoint_entry_add_probe(entry, probe, data);
343 if (IS_ERR(old) && !entry->refcount)
344 remove_tracepoint(entry);
345 return old;
349 * tracepoint_probe_register - Connect a probe to a tracepoint
350 * @name: tracepoint name
351 * @probe: probe handler
353 * Returns 0 if ok, error value on error.
354 * The probe address must at least be aligned on the architecture pointer size.
356 int tracepoint_probe_register(const char *name, void *probe, void *data)
358 struct tracepoint_func *old;
360 mutex_lock(&tracepoints_mutex);
361 old = tracepoint_add_probe(name, probe, data);
362 mutex_unlock(&tracepoints_mutex);
363 if (IS_ERR(old))
364 return PTR_ERR(old);
366 tracepoint_update_probes(); /* may update entry */
367 release_probes(old);
368 return 0;
370 EXPORT_SYMBOL_GPL(tracepoint_probe_register);
372 static struct tracepoint_func *
373 tracepoint_remove_probe(const char *name, void *probe, void *data)
375 struct tracepoint_entry *entry;
376 struct tracepoint_func *old;
378 entry = get_tracepoint(name);
379 if (!entry)
380 return ERR_PTR(-ENOENT);
381 old = tracepoint_entry_remove_probe(entry, probe, data);
382 if (IS_ERR(old))
383 return old;
384 if (!entry->refcount)
385 remove_tracepoint(entry);
386 return old;
390 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
391 * @name: tracepoint name
392 * @probe: probe function pointer
394 * We do not need to call a synchronize_sched to make sure the probes have
395 * finished running before doing a module unload, because the module unload
396 * itself uses stop_machine(), which insures that every preempt disabled section
397 * have finished.
399 int tracepoint_probe_unregister(const char *name, void *probe, void *data)
401 struct tracepoint_func *old;
403 mutex_lock(&tracepoints_mutex);
404 old = tracepoint_remove_probe(name, probe, data);
405 mutex_unlock(&tracepoints_mutex);
406 if (IS_ERR(old))
407 return PTR_ERR(old);
409 tracepoint_update_probes(); /* may update entry */
410 release_probes(old);
411 return 0;
413 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
415 static LIST_HEAD(old_probes);
416 static int need_update;
418 static void tracepoint_add_old_probes(void *old)
420 need_update = 1;
421 if (old) {
422 struct tp_probes *tp_probes = container_of(old,
423 struct tp_probes, probes[0]);
424 list_add(&tp_probes->u.list, &old_probes);
429 * tracepoint_probe_register_noupdate - register a probe but not connect
430 * @name: tracepoint name
431 * @probe: probe handler
433 * caller must call tracepoint_probe_update_all()
435 int tracepoint_probe_register_noupdate(const char *name, void *probe,
436 void *data)
438 struct tracepoint_func *old;
440 mutex_lock(&tracepoints_mutex);
441 old = tracepoint_add_probe(name, probe, data);
442 if (IS_ERR(old)) {
443 mutex_unlock(&tracepoints_mutex);
444 return PTR_ERR(old);
446 tracepoint_add_old_probes(old);
447 mutex_unlock(&tracepoints_mutex);
448 return 0;
450 EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);
453 * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
454 * @name: tracepoint name
455 * @probe: probe function pointer
457 * caller must call tracepoint_probe_update_all()
459 int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
460 void *data)
462 struct tracepoint_func *old;
464 mutex_lock(&tracepoints_mutex);
465 old = tracepoint_remove_probe(name, probe, data);
466 if (IS_ERR(old)) {
467 mutex_unlock(&tracepoints_mutex);
468 return PTR_ERR(old);
470 tracepoint_add_old_probes(old);
471 mutex_unlock(&tracepoints_mutex);
472 return 0;
474 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);
477 * tracepoint_probe_update_all - update tracepoints
479 void tracepoint_probe_update_all(void)
481 LIST_HEAD(release_probes);
482 struct tp_probes *pos, *next;
484 mutex_lock(&tracepoints_mutex);
485 if (!need_update) {
486 mutex_unlock(&tracepoints_mutex);
487 return;
489 if (!list_empty(&old_probes))
490 list_replace_init(&old_probes, &release_probes);
491 need_update = 0;
492 mutex_unlock(&tracepoints_mutex);
494 tracepoint_update_probes();
495 list_for_each_entry_safe(pos, next, &release_probes, u.list) {
496 list_del(&pos->u.list);
497 call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);
500 EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);
503 * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
504 * @tracepoint: current tracepoints (in), next tracepoint (out)
505 * @begin: beginning of the range
506 * @end: end of the range
508 * Returns whether a next tracepoint has been found (1) or not (0).
509 * Will return the first tracepoint in the range if the input tracepoint is
510 * NULL.
512 int tracepoint_get_iter_range(struct tracepoint * const **tracepoint,
513 struct tracepoint * const *begin, struct tracepoint * const *end)
515 if (!*tracepoint && begin != end) {
516 *tracepoint = begin;
517 return 1;
519 if (*tracepoint >= begin && *tracepoint < end)
520 return 1;
521 return 0;
523 EXPORT_SYMBOL_GPL(tracepoint_get_iter_range);
525 static void tracepoint_get_iter(struct tracepoint_iter *iter)
527 int found = 0;
529 /* Core kernel tracepoints */
530 if (!iter->module) {
531 found = tracepoint_get_iter_range(&iter->tracepoint,
532 __start___tracepoints_ptrs,
533 __stop___tracepoints_ptrs);
534 if (found)
535 goto end;
537 /* tracepoints in modules. */
538 found = module_get_iter_tracepoints(iter);
539 end:
540 if (!found)
541 tracepoint_iter_reset(iter);
544 void tracepoint_iter_start(struct tracepoint_iter *iter)
546 tracepoint_get_iter(iter);
548 EXPORT_SYMBOL_GPL(tracepoint_iter_start);
550 void tracepoint_iter_next(struct tracepoint_iter *iter)
552 iter->tracepoint++;
554 * iter->tracepoint may be invalid because we blindly incremented it.
555 * Make sure it is valid by marshalling on the tracepoints, getting the
556 * tracepoints from following modules if necessary.
558 tracepoint_get_iter(iter);
560 EXPORT_SYMBOL_GPL(tracepoint_iter_next);
562 void tracepoint_iter_stop(struct tracepoint_iter *iter)
565 EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
567 void tracepoint_iter_reset(struct tracepoint_iter *iter)
569 iter->module = NULL;
570 iter->tracepoint = NULL;
572 EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
574 #ifdef CONFIG_MODULES
576 int tracepoint_module_notify(struct notifier_block *self,
577 unsigned long val, void *data)
579 struct module *mod = data;
581 switch (val) {
582 case MODULE_STATE_COMING:
583 case MODULE_STATE_GOING:
584 tracepoint_update_probe_range(mod->tracepoints_ptrs,
585 mod->tracepoints_ptrs + mod->num_tracepoints);
586 break;
588 return 0;
591 struct notifier_block tracepoint_module_nb = {
592 .notifier_call = tracepoint_module_notify,
593 .priority = 0,
596 static int init_tracepoints(void)
598 return register_module_notifier(&tracepoint_module_nb);
600 __initcall(init_tracepoints);
602 #endif /* CONFIG_MODULES */
604 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
606 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
607 static int sys_tracepoint_refcount;
609 void syscall_regfunc(void)
611 unsigned long flags;
612 struct task_struct *g, *t;
614 if (!sys_tracepoint_refcount) {
615 read_lock_irqsave(&tasklist_lock, flags);
616 do_each_thread(g, t) {
617 /* Skip kernel threads. */
618 if (t->mm)
619 set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
620 } while_each_thread(g, t);
621 read_unlock_irqrestore(&tasklist_lock, flags);
623 sys_tracepoint_refcount++;
626 void syscall_unregfunc(void)
628 unsigned long flags;
629 struct task_struct *g, *t;
631 sys_tracepoint_refcount--;
632 if (!sys_tracepoint_refcount) {
633 read_lock_irqsave(&tasklist_lock, flags);
634 do_each_thread(g, t) {
635 clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
636 } while_each_thread(g, t);
637 read_unlock_irqrestore(&tasklist_lock, flags);
640 #endif