2 * Copyright (C) 2008-2011 Mathieu Desnoyers
3 * Copyright (C) 2009 Pierre-Marc Fournier
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation;
8 * version 2.1 of the License.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 * Ported to userspace by Pierre-Marc Fournier.
28 #include <urcu/arch.h>
29 #include <lttng/urcu/urcu-ust.h>
30 #include <urcu/hlist.h>
31 #include <urcu/uatomic.h>
32 #include <urcu/compiler.h>
33 #include <urcu/system.h>
35 #include <lttng/tracepoint.h>
36 #include <lttng/ust-abi.h> /* for LTTNG_UST_SYM_NAME_LEN */
38 #include <usterr-signal-safe.h>
41 #include "tracepoint-internal.h"
42 #include "lttng-tracer-core.h"
46 /* Test compiler support for weak symbols with hidden visibility. */
47 int __tracepoint_test_symbol1
__attribute__((weak
, visibility("hidden")));
48 void *__tracepoint_test_symbol2
__attribute__((weak
, visibility("hidden")));
51 } __tracepoint_test_symbol3
__attribute__((weak
, visibility("hidden")));
53 /* Set to 1 to enable tracepoint debug output */
54 static const int tracepoint_debug
;
55 static int initialized
;
58 * If tracepoint_destructors_state = 1, tracepoint destructors are
59 * enabled. They are disabled otherwise.
61 static int tracepoint_destructors_state
= 1;
64 * Expose the now deprecated symbol __tracepoints__disable_destructors for
65 * backward compatibility of applications built against old versions of
66 * lttng-ust. We need to keep __tracepoints__disable_destructors up to date
67 * within the new destructor disabling API because old applications read this
70 int __tracepoints__disable_destructors
__attribute__((weak
));
72 static void (*new_tracepoint_cb
)(struct lttng_ust_tracepoint
*);
75 * tracepoint_mutex nests inside UST mutex.
77 * Note about interaction with fork/clone: UST does not hold the
78 * tracepoint mutex across fork/clone because it is either:
79 * - nested within UST mutex, in which case holding the UST mutex across
81 * - taken by a library constructor, which should never race with a
82 * fork/clone if the application is expected to continue running with
83 * the same memory layout (no following exec()).
85 static pthread_mutex_t tracepoint_mutex
= PTHREAD_MUTEX_INITIALIZER
;
88 * libraries that contain tracepoints (struct tracepoint_lib).
89 * Protected by tracepoint mutex.
91 static CDS_LIST_HEAD(libs
);
94 * The tracepoint mutex protects the library tracepoints, the hash table, and
96 * All calls to the tracepoint API must be protected by the tracepoint mutex,
97 * excepts calls to tracepoint_register_lib and
98 * tracepoint_unregister_lib, which take the tracepoint mutex themselves.
102 * Tracepoint hash table, containing the active tracepoints.
103 * Protected by tracepoint mutex.
105 #define TRACEPOINT_HASH_BITS 12
106 #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
107 static struct cds_hlist_head tracepoint_table
[TRACEPOINT_TABLE_SIZE
];
109 static CDS_LIST_HEAD(old_probes
);
110 static int need_update
;
112 static CDS_LIST_HEAD(release_queue
);
113 static int release_queue_need_update
;
117 * It is used to to delay the free of multiple probes array until a quiescent
119 * Tracepoint entries modifications are protected by the tracepoint mutex.
121 struct tracepoint_entry
{
122 struct cds_hlist_node hlist
;
123 struct lttng_ust_tracepoint_probe
*probes
;
124 int refcount
; /* Number of times armed. 0 if disarmed. */
125 int callsite_refcount
; /* how many libs use this tracepoint */
132 struct cds_list_head list
;
133 /* Field below only used for call_rcu scheme */
134 /* struct rcu_head head; */
136 struct lttng_ust_tracepoint_probe probes
[0];
140 * Callsite hash table, containing the tracepoint call sites.
141 * Protected by tracepoint mutex.
143 #define CALLSITE_HASH_BITS 12
144 #define CALLSITE_TABLE_SIZE (1 << CALLSITE_HASH_BITS)
145 static struct cds_hlist_head callsite_table
[CALLSITE_TABLE_SIZE
];
147 struct callsite_entry
{
148 struct cds_hlist_node hlist
; /* hash table node */
149 struct cds_list_head node
; /* lib list of callsites node */
150 struct lttng_ust_tracepoint
*tp
;
151 bool tp_entry_callsite_ref
; /* Has a tp_entry took a ref on this callsite */
154 static int tracepoint_v1_api_used
;
155 static void (*lttng_ust_liburcu_bp_synchronize_rcu
)(void);
156 static void (*lttng_ust_liburcu_bp_rcu_read_lock
)(void);
157 static void (*lttng_ust_liburcu_bp_rcu_read_unlock
)(void);
158 void (*lttng_ust_liburcu_bp_before_fork
)(void);
159 void (*lttng_ust_liburcu_bp_after_fork_parent
)(void);
160 void (*lttng_ust_liburcu_bp_after_fork_child
)(void);
162 static bool lttng_ust_tracepoint_v1_used(void)
164 return uatomic_read(&tracepoint_v1_api_used
);
167 static void lttng_ust_tracepoint_set_v1_used(void)
169 if (!lttng_ust_tracepoint_v1_used()) {
171 * Perform dlsym here rather than lazily on first use to
172 * eliminate nesting of dynamic loader lock (used within
173 * dlsym) inside the ust lock.
175 if (!lttng_ust_liburcu_bp_synchronize_rcu
) {
176 lttng_ust_liburcu_bp_synchronize_rcu
= URCU_FORCE_CAST(void (*)(void),
177 dlsym(RTLD_DEFAULT
, "synchronize_rcu_bp"));
179 * Allow legacy applications compiled without
180 * _LGPL_SOURCE to use v1 API. Those are not
181 * required to be linked against liburcu-bp,
182 * so in those situations the liburcu-bp symbols
183 * are not present in the global symbol table,
184 * and we do not need to call urcu-bp
187 * However, nothing prevents a _LGPL_SOURCE
188 * instrumented library loaded afterwards to
189 * require liburcu-bp, so we need to check again
192 if (!lttng_ust_liburcu_bp_synchronize_rcu
)
195 if (!lttng_ust_liburcu_bp_before_fork
) {
196 lttng_ust_liburcu_bp_before_fork
= URCU_FORCE_CAST(void (*)(void),
197 dlsym(RTLD_DEFAULT
, "rcu_bp_before_fork"));
198 if (!lttng_ust_liburcu_bp_before_fork
)
201 if (!lttng_ust_liburcu_bp_after_fork_parent
) {
202 lttng_ust_liburcu_bp_after_fork_parent
= URCU_FORCE_CAST(void (*)(void),
203 dlsym(RTLD_DEFAULT
, "rcu_bp_after_fork_parent"));
204 if (!lttng_ust_liburcu_bp_after_fork_parent
)
207 if (!lttng_ust_liburcu_bp_after_fork_child
) {
208 lttng_ust_liburcu_bp_after_fork_child
= URCU_FORCE_CAST(void (*)(void),
209 dlsym(RTLD_DEFAULT
, "rcu_bp_after_fork_child"));
210 if (!lttng_ust_liburcu_bp_after_fork_child
)
213 if (!lttng_ust_liburcu_bp_rcu_read_lock
) {
214 lttng_ust_liburcu_bp_rcu_read_lock
= URCU_FORCE_CAST(void (*)(void),
215 dlsym(RTLD_DEFAULT
, "rcu_read_lock_bp"));
216 if (!lttng_ust_liburcu_bp_rcu_read_lock
)
219 if (!lttng_ust_liburcu_bp_rcu_read_unlock
) {
220 lttng_ust_liburcu_bp_rcu_read_unlock
= URCU_FORCE_CAST(void (*)(void),
221 dlsym(RTLD_DEFAULT
, "rcu_read_unlock_bp"));
222 if (!lttng_ust_liburcu_bp_rcu_read_unlock
)
226 /* Fixup URCU bp TLS. */
227 lttng_ust_liburcu_bp_rcu_read_lock();
228 lttng_ust_liburcu_bp_rcu_read_unlock();
230 uatomic_set(&tracepoint_v1_api_used
, 1);
234 /* coverity[+alloc] */
235 static void *allocate_probes(int count
)
237 struct tp_probes
*p
=
238 zmalloc(count
* sizeof(struct lttng_ust_tracepoint_probe
)
239 + sizeof(struct tp_probes
));
240 return p
== NULL
? NULL
: p
->probes
;
243 /* coverity[+free : arg-0] */
244 static void release_probes(void *old
)
247 struct tp_probes
*tp_probes
= caa_container_of(old
,
248 struct tp_probes
, probes
[0]);
249 lttng_ust_synchronize_trace();
254 static void debug_print_probes(struct tracepoint_entry
*entry
)
258 if (!tracepoint_debug
|| !entry
->probes
)
261 for (i
= 0; entry
->probes
[i
].func
; i
++)
262 DBG("Probe %d : %p", i
, entry
->probes
[i
].func
);
266 tracepoint_entry_add_probe(struct tracepoint_entry
*entry
,
267 void (*probe
)(void), void *data
)
270 struct lttng_ust_tracepoint_probe
*old
, *new;
274 return ERR_PTR(-EINVAL
);
276 debug_print_probes(entry
);
279 /* (N -> N+1), (N != 0, 1) probes */
280 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++)
281 if (old
[nr_probes
].func
== probe
&&
282 old
[nr_probes
].data
== data
)
283 return ERR_PTR(-EEXIST
);
285 /* + 2 : one for new probe, one for NULL func */
286 new = allocate_probes(nr_probes
+ 2);
288 return ERR_PTR(-ENOMEM
);
291 nr_probes
* sizeof(struct lttng_ust_tracepoint_probe
));
292 new[nr_probes
].func
= probe
;
293 new[nr_probes
].data
= data
;
294 new[nr_probes
+ 1].func
= NULL
;
295 entry
->refcount
= nr_probes
+ 1;
297 debug_print_probes(entry
);
302 tracepoint_entry_remove_probe(struct tracepoint_entry
*entry
,
303 void (*probe
)(void), void *data
)
305 int nr_probes
= 0, nr_del
= 0, i
;
306 struct lttng_ust_tracepoint_probe
*old
, *new;
311 return ERR_PTR(-ENOENT
);
313 debug_print_probes(entry
);
314 /* (N -> M), (N > 1, M >= 0) probes */
316 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++) {
317 if (old
[nr_probes
].func
== probe
&&
318 old
[nr_probes
].data
== data
)
323 if (nr_probes
- nr_del
== 0) {
324 /* N -> 0, (N > 1) */
325 entry
->probes
= NULL
;
327 debug_print_probes(entry
);
331 /* N -> M, (N > 1, M > 0) */
333 new = allocate_probes(nr_probes
- nr_del
+ 1);
335 return ERR_PTR(-ENOMEM
);
336 for (i
= 0; old
[i
].func
; i
++)
337 if (old
[i
].func
!= probe
|| old
[i
].data
!= data
)
339 new[nr_probes
- nr_del
].func
= NULL
;
340 entry
->refcount
= nr_probes
- nr_del
;
343 debug_print_probes(entry
);
348 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
349 * Must be called with tracepoint mutex held.
350 * Returns NULL if not present.
352 static struct tracepoint_entry
*get_tracepoint(const char *name
)
354 struct cds_hlist_head
*head
;
355 struct cds_hlist_node
*node
;
356 struct tracepoint_entry
*e
;
357 size_t name_len
= strlen(name
);
360 if (name_len
> LTTNG_UST_SYM_NAME_LEN
- 1) {
361 WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name
, LTTNG_UST_SYM_NAME_LEN
- 1);
362 name_len
= LTTNG_UST_SYM_NAME_LEN
- 1;
364 hash
= jhash(name
, name_len
, 0);
365 head
= &tracepoint_table
[hash
& (TRACEPOINT_TABLE_SIZE
- 1)];
366 cds_hlist_for_each_entry(e
, node
, head
, hlist
) {
367 if (!strncmp(name
, e
->name
, LTTNG_UST_SYM_NAME_LEN
- 1))
374 * Add the tracepoint to the tracepoint hash table. Must be called with
375 * tracepoint mutex held.
377 static struct tracepoint_entry
*add_tracepoint(const char *name
,
378 const char *signature
)
380 struct cds_hlist_head
*head
;
381 struct cds_hlist_node
*node
;
382 struct tracepoint_entry
*e
;
383 size_t name_len
= strlen(name
);
384 size_t sig_len
= strlen(signature
);
385 size_t sig_off
, name_off
;
388 if (name_len
> LTTNG_UST_SYM_NAME_LEN
- 1) {
389 WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name
, LTTNG_UST_SYM_NAME_LEN
- 1);
390 name_len
= LTTNG_UST_SYM_NAME_LEN
- 1;
392 hash
= jhash(name
, name_len
, 0);
393 head
= &tracepoint_table
[hash
& (TRACEPOINT_TABLE_SIZE
- 1)];
394 cds_hlist_for_each_entry(e
, node
, head
, hlist
) {
395 if (!strncmp(name
, e
->name
, LTTNG_UST_SYM_NAME_LEN
- 1)) {
396 DBG("tracepoint %s busy", name
);
397 return ERR_PTR(-EEXIST
); /* Already there */
402 * Using zmalloc here to allocate a variable length elements: name and
403 * signature. Could cause some memory fragmentation if overused.
405 name_off
= sizeof(struct tracepoint_entry
);
406 sig_off
= name_off
+ name_len
+ 1;
408 e
= zmalloc(sizeof(struct tracepoint_entry
) + name_len
+ 1 + sig_len
+ 1);
410 return ERR_PTR(-ENOMEM
);
411 e
->name
= (char *) e
+ name_off
;
412 memcpy(e
->name
, name
, name_len
+ 1);
413 e
->name
[name_len
] = '\0';
415 e
->signature
= (char *) e
+ sig_off
;
416 memcpy(e
->signature
, signature
, sig_len
+ 1);
417 e
->signature
[sig_len
] = '\0';
421 e
->callsite_refcount
= 0;
423 cds_hlist_add_head(&e
->hlist
, head
);
428 * Remove the tracepoint from the tracepoint hash table. Must be called with
429 * tracepoint mutex held.
431 static void remove_tracepoint(struct tracepoint_entry
*e
)
433 cds_hlist_del(&e
->hlist
);
438 * Sets the probe callback corresponding to one tracepoint.
440 static void set_tracepoint(struct tracepoint_entry
**entry
,
441 struct lttng_ust_tracepoint
*elem
, int active
)
443 WARN_ON(strncmp((*entry
)->name
, elem
->name
, LTTNG_UST_SYM_NAME_LEN
- 1) != 0);
445 * Check that signatures match before connecting a probe to a
446 * tracepoint. Warn the user if they don't.
448 if (strcmp(elem
->signature
, (*entry
)->signature
) != 0) {
449 static int warned
= 0;
451 /* Only print once, don't flood console. */
453 WARN("Tracepoint signature mismatch, not enabling one or more tracepoints. Ensure that the tracepoint probes prototypes match the application.");
454 WARN("Tracepoint \"%s\" signatures: call: \"%s\" vs probe: \"%s\".",
455 elem
->name
, elem
->signature
, (*entry
)->signature
);
458 /* Don't accept connecting non-matching signatures. */
463 * rcu_assign_pointer has a cmm_smp_wmb() which makes sure that the new
464 * probe callbacks array is consistent before setting a pointer to it.
465 * This array is referenced by __DO_TRACE from
466 * include/linux/tracepoints.h. A matching cmm_smp_read_barrier_depends()
469 lttng_ust_rcu_assign_pointer(elem
->probes
, (*entry
)->probes
);
470 CMM_STORE_SHARED(elem
->state
, active
);
474 * Disable a tracepoint and its probe callback.
475 * Note: only waiting an RCU period after setting elem->call to the empty
476 * function insures that the original callback is not used anymore. This insured
477 * by preempt_disable around the call site.
479 static void disable_tracepoint(struct lttng_ust_tracepoint
*elem
)
481 CMM_STORE_SHARED(elem
->state
, 0);
482 lttng_ust_rcu_assign_pointer(elem
->probes
, NULL
);
486 * Add the callsite to the callsite hash table. Must be called with
487 * tracepoint mutex held.
489 static void add_callsite(struct tracepoint_lib
* lib
, struct lttng_ust_tracepoint
*tp
)
491 struct cds_hlist_head
*head
;
492 struct callsite_entry
*e
;
493 const char *name
= tp
->name
;
494 size_t name_len
= strlen(name
);
496 struct tracepoint_entry
*tp_entry
;
498 if (name_len
> LTTNG_UST_SYM_NAME_LEN
- 1) {
499 WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name
, LTTNG_UST_SYM_NAME_LEN
- 1);
500 name_len
= LTTNG_UST_SYM_NAME_LEN
- 1;
502 hash
= jhash(name
, name_len
, 0);
503 head
= &callsite_table
[hash
& (CALLSITE_TABLE_SIZE
- 1)];
504 e
= zmalloc(sizeof(struct callsite_entry
));
506 PERROR("Unable to add callsite for tracepoint \"%s\"", name
);
509 cds_hlist_add_head(&e
->hlist
, head
);
511 cds_list_add(&e
->node
, &lib
->callsites
);
513 tp_entry
= get_tracepoint(name
);
516 tp_entry
->callsite_refcount
++;
517 e
->tp_entry_callsite_ref
= true;
521 * Remove the callsite from the callsite hash table and from lib
522 * callsite list. Must be called with tracepoint mutex held.
524 static void remove_callsite(struct callsite_entry
*e
)
526 struct tracepoint_entry
*tp_entry
;
528 tp_entry
= get_tracepoint(e
->tp
->name
);
530 if (e
->tp_entry_callsite_ref
)
531 tp_entry
->callsite_refcount
--;
532 if (tp_entry
->callsite_refcount
== 0)
533 disable_tracepoint(e
->tp
);
535 cds_hlist_del(&e
->hlist
);
536 cds_list_del(&e
->node
);
541 * Enable/disable all callsites based on the state of a specific
543 * Must be called with tracepoint mutex held.
545 static void tracepoint_sync_callsites(const char *name
)
547 struct cds_hlist_head
*head
;
548 struct cds_hlist_node
*node
;
549 struct callsite_entry
*e
;
550 size_t name_len
= strlen(name
);
552 struct tracepoint_entry
*tp_entry
;
554 tp_entry
= get_tracepoint(name
);
555 if (name_len
> LTTNG_UST_SYM_NAME_LEN
- 1) {
556 WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name
, LTTNG_UST_SYM_NAME_LEN
- 1);
557 name_len
= LTTNG_UST_SYM_NAME_LEN
- 1;
559 hash
= jhash(name
, name_len
, 0);
560 head
= &callsite_table
[hash
& (CALLSITE_TABLE_SIZE
- 1)];
561 cds_hlist_for_each_entry(e
, node
, head
, hlist
) {
562 struct lttng_ust_tracepoint
*tp
= e
->tp
;
564 if (strncmp(name
, tp
->name
, LTTNG_UST_SYM_NAME_LEN
- 1))
567 if (!e
->tp_entry_callsite_ref
) {
568 tp_entry
->callsite_refcount
++;
569 e
->tp_entry_callsite_ref
= true;
571 set_tracepoint(&tp_entry
, tp
,
572 !!tp_entry
->refcount
);
574 disable_tracepoint(tp
);
575 e
->tp_entry_callsite_ref
= false;
581 * tracepoint_update_probe_range - Update a probe range
582 * @begin: beginning of the range
583 * @end: end of the range
585 * Updates the probe callback corresponding to a range of tracepoints.
588 void tracepoint_update_probe_range(struct lttng_ust_tracepoint
* const *begin
,
589 struct lttng_ust_tracepoint
* const *end
)
591 struct lttng_ust_tracepoint
* const *iter
;
592 struct tracepoint_entry
*mark_entry
;
594 for (iter
= begin
; iter
< end
; iter
++) {
596 continue; /* skip dummy */
597 if (!(*iter
)->name
) {
598 disable_tracepoint(*iter
);
601 mark_entry
= get_tracepoint((*iter
)->name
);
603 set_tracepoint(&mark_entry
, *iter
,
604 !!mark_entry
->refcount
);
606 disable_tracepoint(*iter
);
611 static void lib_update_tracepoints(struct tracepoint_lib
*lib
)
613 tracepoint_update_probe_range(lib
->tracepoints_start
,
614 lib
->tracepoints_start
+ lib
->tracepoints_count
);
617 static void lib_register_callsites(struct tracepoint_lib
*lib
)
619 struct lttng_ust_tracepoint
* const *begin
;
620 struct lttng_ust_tracepoint
* const *end
;
621 struct lttng_ust_tracepoint
* const *iter
;
623 begin
= lib
->tracepoints_start
;
624 end
= lib
->tracepoints_start
+ lib
->tracepoints_count
;
626 for (iter
= begin
; iter
< end
; iter
++) {
628 continue; /* skip dummy */
629 if (!(*iter
)->name
) {
632 add_callsite(lib
, *iter
);
636 static void lib_unregister_callsites(struct tracepoint_lib
*lib
)
638 struct callsite_entry
*callsite
, *tmp
;
640 cds_list_for_each_entry_safe(callsite
, tmp
, &lib
->callsites
, node
)
641 remove_callsite(callsite
);
645 * Update probes, removing the faulty probes.
647 static void tracepoint_update_probes(void)
649 struct tracepoint_lib
*lib
;
651 /* tracepoints registered from libraries and executable. */
652 cds_list_for_each_entry(lib
, &libs
, list
)
653 lib_update_tracepoints(lib
);
656 static struct lttng_ust_tracepoint_probe
*
657 tracepoint_add_probe(const char *name
, void (*probe
)(void), void *data
,
658 const char *signature
)
660 struct tracepoint_entry
*entry
;
661 struct lttng_ust_tracepoint_probe
*old
;
663 entry
= get_tracepoint(name
);
665 if (strcmp(entry
->signature
, signature
) != 0) {
666 ERR("Tracepoint and probe signature do not match.");
667 return ERR_PTR(-EINVAL
);
670 entry
= add_tracepoint(name
, signature
);
672 return (struct lttng_ust_tracepoint_probe
*)entry
;
674 old
= tracepoint_entry_add_probe(entry
, probe
, data
);
675 if (IS_ERR(old
) && !entry
->refcount
)
676 remove_tracepoint(entry
);
680 static void tracepoint_release_queue_add_old_probes(void *old
)
682 release_queue_need_update
= 1;
684 struct tp_probes
*tp_probes
= caa_container_of(old
,
685 struct tp_probes
, probes
[0]);
686 cds_list_add(&tp_probes
->u
.list
, &release_queue
);
691 * __tracepoint_probe_register - Connect a probe to a tracepoint
692 * @name: tracepoint name
693 * @probe: probe handler
695 * Returns 0 if ok, error value on error.
696 * The probe address must at least be aligned on the architecture pointer size.
697 * Called with the tracepoint mutex held.
699 int __tracepoint_probe_register(const char *name
, void (*probe
)(void),
700 void *data
, const char *signature
)
705 DBG("Registering probe to tracepoint %s", name
);
707 pthread_mutex_lock(&tracepoint_mutex
);
708 old
= tracepoint_add_probe(name
, probe
, data
, signature
);
714 tracepoint_sync_callsites(name
);
717 pthread_mutex_unlock(&tracepoint_mutex
);
722 * Caller needs to invoke __tracepoint_probe_release_queue() after
723 * calling __tracepoint_probe_register_queue_release() one or multiple
724 * times to ensure it does not leak memory.
726 int __tracepoint_probe_register_queue_release(const char *name
,
727 void (*probe
)(void), void *data
, const char *signature
)
732 DBG("Registering probe to tracepoint %s. Queuing release.", name
);
734 pthread_mutex_lock(&tracepoint_mutex
);
735 old
= tracepoint_add_probe(name
, probe
, data
, signature
);
741 tracepoint_sync_callsites(name
);
742 tracepoint_release_queue_add_old_probes(old
);
744 pthread_mutex_unlock(&tracepoint_mutex
);
748 static void *tracepoint_remove_probe(const char *name
, void (*probe
)(void),
751 struct tracepoint_entry
*entry
;
754 entry
= get_tracepoint(name
);
756 return ERR_PTR(-ENOENT
);
757 old
= tracepoint_entry_remove_probe(entry
, probe
, data
);
760 if (!entry
->refcount
)
761 remove_tracepoint(entry
);
766 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
767 * @name: tracepoint name
768 * @probe: probe function pointer
769 * @probe: probe data pointer
771 int __tracepoint_probe_unregister(const char *name
, void (*probe
)(void),
777 DBG("Un-registering probe from tracepoint %s", name
);
779 pthread_mutex_lock(&tracepoint_mutex
);
780 old
= tracepoint_remove_probe(name
, probe
, data
);
785 tracepoint_sync_callsites(name
);
788 pthread_mutex_unlock(&tracepoint_mutex
);
793 * Caller needs to invoke __tracepoint_probe_release_queue() after
794 * calling __tracepoint_probe_unregister_queue_release() one or multiple
795 * times to ensure it does not leak memory.
797 int __tracepoint_probe_unregister_queue_release(const char *name
,
798 void (*probe
)(void), void *data
)
803 DBG("Un-registering probe from tracepoint %s. Queuing release.", name
);
805 pthread_mutex_lock(&tracepoint_mutex
);
806 old
= tracepoint_remove_probe(name
, probe
, data
);
811 tracepoint_sync_callsites(name
);
812 tracepoint_release_queue_add_old_probes(old
);
814 pthread_mutex_unlock(&tracepoint_mutex
);
818 void __tracepoint_probe_prune_release_queue(void)
820 CDS_LIST_HEAD(release_probes
);
821 struct tp_probes
*pos
, *next
;
823 DBG("Release queue of unregistered tracepoint probes.");
825 pthread_mutex_lock(&tracepoint_mutex
);
826 if (!release_queue_need_update
)
828 if (!cds_list_empty(&release_queue
))
829 cds_list_replace_init(&release_queue
, &release_probes
);
830 release_queue_need_update
= 0;
832 /* Wait for grace period between all sync_callsites and free. */
833 lttng_ust_synchronize_trace();
835 cds_list_for_each_entry_safe(pos
, next
, &release_probes
, u
.list
) {
836 cds_list_del(&pos
->u
.list
);
840 pthread_mutex_unlock(&tracepoint_mutex
);
843 static void tracepoint_add_old_probes(void *old
)
847 struct tp_probes
*tp_probes
= caa_container_of(old
,
848 struct tp_probes
, probes
[0]);
849 cds_list_add(&tp_probes
->u
.list
, &old_probes
);
854 * tracepoint_probe_register_noupdate - register a probe but not connect
855 * @name: tracepoint name
856 * @probe: probe handler
858 * caller must call tracepoint_probe_update_all()
860 int tracepoint_probe_register_noupdate(const char *name
, void (*probe
)(void),
861 void *data
, const char *signature
)
866 pthread_mutex_lock(&tracepoint_mutex
);
867 old
= tracepoint_add_probe(name
, probe
, data
, signature
);
872 tracepoint_add_old_probes(old
);
874 pthread_mutex_unlock(&tracepoint_mutex
);
879 * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
880 * @name: tracepoint name
881 * @probe: probe function pointer
883 * caller must call tracepoint_probe_update_all()
884 * Called with the tracepoint mutex held.
886 int tracepoint_probe_unregister_noupdate(const char *name
, void (*probe
)(void),
892 DBG("Un-registering probe from tracepoint %s", name
);
894 pthread_mutex_lock(&tracepoint_mutex
);
895 old
= tracepoint_remove_probe(name
, probe
, data
);
900 tracepoint_add_old_probes(old
);
902 pthread_mutex_unlock(&tracepoint_mutex
);
907 * tracepoint_probe_update_all - update tracepoints
909 void tracepoint_probe_update_all(void)
911 CDS_LIST_HEAD(release_probes
);
912 struct tp_probes
*pos
, *next
;
914 pthread_mutex_lock(&tracepoint_mutex
);
918 if (!cds_list_empty(&old_probes
))
919 cds_list_replace_init(&old_probes
, &release_probes
);
922 tracepoint_update_probes();
923 /* Wait for grace period between update_probes and free. */
924 lttng_ust_synchronize_trace();
925 cds_list_for_each_entry_safe(pos
, next
, &release_probes
, u
.list
) {
926 cds_list_del(&pos
->u
.list
);
930 pthread_mutex_unlock(&tracepoint_mutex
);
933 void tracepoint_set_new_tracepoint_cb(void (*cb
)(struct lttng_ust_tracepoint
*))
935 new_tracepoint_cb
= cb
;
938 static void new_tracepoints(struct lttng_ust_tracepoint
* const *start
,
939 struct lttng_ust_tracepoint
* const *end
)
941 if (new_tracepoint_cb
) {
942 struct lttng_ust_tracepoint
* const *t
;
944 for (t
= start
; t
< end
; t
++) {
946 new_tracepoint_cb(*t
);
952 * tracepoint_{un,}register_lib is meant to be looked up by instrumented
953 * applications through dlsym(). If found, those can register their
954 * tracepoints, else those tracepoints will not be available for
955 * tracing. The number at the end of those symbols acts as a major
956 * version for tracepoints.
958 * Older instrumented applications should still work with newer
959 * liblttng-ust, but it is fine that instrumented applications compiled
960 * against recent liblttng-ust headers require a recent liblttng-ust
961 * runtime for those tracepoints to be taken into account.
963 int tracepoint_register_lib2(struct lttng_ust_tracepoint
* const *tracepoints_start
,
964 int tracepoints_count
)
966 struct tracepoint_lib
*pl
, *iter
;
970 pl
= (struct tracepoint_lib
*) zmalloc(sizeof(struct tracepoint_lib
));
972 PERROR("Unable to register tracepoint lib");
975 pl
->tracepoints_start
= tracepoints_start
;
976 pl
->tracepoints_count
= tracepoints_count
;
977 CDS_INIT_LIST_HEAD(&pl
->callsites
);
979 pthread_mutex_lock(&tracepoint_mutex
);
981 * We sort the libs by struct lib pointer address.
983 cds_list_for_each_entry_reverse(iter
, &libs
, list
) {
984 BUG_ON(iter
== pl
); /* Should never be in the list twice */
986 /* We belong to the location right after iter. */
987 cds_list_add(&pl
->list
, &iter
->list
);
991 /* We should be added at the head of the list */
992 cds_list_add(&pl
->list
, &libs
);
994 new_tracepoints(tracepoints_start
, tracepoints_start
+ tracepoints_count
);
995 lib_register_callsites(pl
);
996 lib_update_tracepoints(pl
);
997 pthread_mutex_unlock(&tracepoint_mutex
);
999 DBG("just registered a tracepoints section from %p and having %d tracepoints",
1000 tracepoints_start
, tracepoints_count
);
1004 for (i
= 0; i
< tracepoints_count
; i
++) {
1005 DBG("registered tracepoint: %s", tracepoints_start
[i
]->name
);
1012 /* Exposed for backward compatibility with old instrumented applications. */
1013 int tracepoint_register_lib(struct lttng_ust_tracepoint
* const *tracepoints_start
,
1014 int tracepoints_count
)
1016 lttng_ust_tracepoint_set_v1_used();
1017 return tracepoint_register_lib2(tracepoints_start
, tracepoints_count
);
1020 int tracepoint_unregister_lib2(struct lttng_ust_tracepoint
* const *tracepoints_start
)
1022 struct tracepoint_lib
*lib
;
1024 pthread_mutex_lock(&tracepoint_mutex
);
1025 cds_list_for_each_entry(lib
, &libs
, list
) {
1026 if (lib
->tracepoints_start
!= tracepoints_start
)
1029 cds_list_del(&lib
->list
);
1031 * Unregistering a callsite also decreases the
1032 * callsite reference count of the corresponding
1033 * tracepoint, and disables the tracepoint if
1034 * the reference count drops to zero.
1036 lib_unregister_callsites(lib
);
1037 DBG("just unregistered a tracepoints section from %p",
1038 lib
->tracepoints_start
);
1042 pthread_mutex_unlock(&tracepoint_mutex
);
1046 /* Exposed for backward compatibility with old instrumented applications. */
1047 int tracepoint_unregister_lib(struct lttng_ust_tracepoint
* const *tracepoints_start
)
1049 lttng_ust_tracepoint_set_v1_used();
1050 return tracepoint_unregister_lib2(tracepoints_start
);
1054 * Report in debug message whether the compiler correctly supports weak
1055 * hidden symbols. This test checks that the address associated with two
1056 * weak symbols with hidden visibility is the same when declared within
1057 * two compile units part of the same module.
1059 static void check_weak_hidden(void)
1061 DBG("Your compiler treats weak symbols with hidden visibility for integer objects as %s between compile units part of the same module.",
1062 &__tracepoint_test_symbol1
== lttng_ust_tp_check_weak_hidden1() ?
1064 "DIFFERENT addresses");
1065 DBG("Your compiler treats weak symbols with hidden visibility for pointer objects as %s between compile units part of the same module.",
1066 &__tracepoint_test_symbol2
== lttng_ust_tp_check_weak_hidden2() ?
1068 "DIFFERENT addresses");
1069 DBG("Your compiler treats weak symbols with hidden visibility for 24-byte structure objects as %s between compile units part of the same module.",
1070 &__tracepoint_test_symbol3
== lttng_ust_tp_check_weak_hidden3() ?
1072 "DIFFERENT addresses");
1075 void init_tracepoint(void)
1077 if (uatomic_xchg(&initialized
, 1) == 1)
1080 check_weak_hidden();
1083 void exit_tracepoint(void)
1089 * Create the wrapper symbols.
1091 #undef tp_rcu_read_lock
1092 #undef tp_rcu_read_unlock
1093 #undef tp_rcu_dereference
1095 void tp_rcu_read_lock(void)
1097 lttng_ust_urcu_read_lock();
1100 void tp_rcu_read_unlock(void)
1102 lttng_ust_urcu_read_unlock();
1105 void *tp_rcu_dereference_sym(void *p
)
1107 return lttng_ust_rcu_dereference(p
);
1111 * Programs that have threads that survive after they exit, and therefore call
1112 * library destructors, should disable the tracepoint destructors by calling
1113 * tp_disable_destructors(). This will leak the tracepoint
1114 * instrumentation library shared object, leaving its teardown to the operating
1115 * system process teardown.
1117 * To access and/or modify this value, users need to use a combination of
1118 * dlopen(3) and dlsym(3) to get an handle on the
1119 * tp_disable_destructors and tp_get_destructors_state symbols below.
1121 void tp_disable_destructors(void)
1123 uatomic_set(&tracepoint_destructors_state
, 0);
1127 * Returns 1 if the destructors are enabled and should be executed.
1128 * Returns 0 if the destructors are disabled.
1130 int tp_get_destructors_state(void)
1132 return uatomic_read(&tracepoint_destructors_state
);
1135 void lttng_ust_synchronize_trace(void)
1137 lttng_ust_urcu_synchronize_rcu();
1139 * For legacy tracepoint instrumentation, also wait for urcu-bp
1142 if (lttng_ust_liburcu_bp_synchronize_rcu
)
1143 lttng_ust_liburcu_bp_synchronize_rcu();
1147 * Create the wrapper symbols for legacy v1 API.
1149 void tp_rcu_read_lock_bp(void)
1151 lttng_ust_urcu_read_lock();
1154 void tp_rcu_read_unlock_bp(void)
1156 lttng_ust_urcu_read_unlock();
1159 void *tp_rcu_dereference_sym_bp(void *p
)
1161 return lttng_ust_rcu_dereference(p
);