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"));
178 if (!lttng_ust_liburcu_bp_synchronize_rcu
)
181 if (!lttng_ust_liburcu_bp_before_fork
) {
182 lttng_ust_liburcu_bp_before_fork
= URCU_FORCE_CAST(void (*)(void),
183 dlsym(RTLD_DEFAULT
, "rcu_bp_before_fork"));
184 if (!lttng_ust_liburcu_bp_before_fork
)
187 if (!lttng_ust_liburcu_bp_after_fork_parent
) {
188 lttng_ust_liburcu_bp_after_fork_parent
= URCU_FORCE_CAST(void (*)(void),
189 dlsym(RTLD_DEFAULT
, "rcu_bp_after_fork_parent"));
190 if (!lttng_ust_liburcu_bp_after_fork_parent
)
193 if (!lttng_ust_liburcu_bp_after_fork_child
) {
194 lttng_ust_liburcu_bp_after_fork_child
= URCU_FORCE_CAST(void (*)(void),
195 dlsym(RTLD_DEFAULT
, "rcu_bp_after_fork_child"));
196 if (!lttng_ust_liburcu_bp_after_fork_child
)
199 if (!lttng_ust_liburcu_bp_rcu_read_lock
) {
200 lttng_ust_liburcu_bp_rcu_read_lock
= URCU_FORCE_CAST(void (*)(void),
201 dlsym(RTLD_DEFAULT
, "rcu_read_lock_bp"));
202 if (!lttng_ust_liburcu_bp_rcu_read_lock
)
205 if (!lttng_ust_liburcu_bp_rcu_read_unlock
) {
206 lttng_ust_liburcu_bp_rcu_read_unlock
= URCU_FORCE_CAST(void (*)(void),
207 dlsym(RTLD_DEFAULT
, "rcu_read_unlock_bp"));
208 if (!lttng_ust_liburcu_bp_rcu_read_unlock
)
212 /* Fixup URCU bp TLS. */
213 lttng_ust_liburcu_bp_rcu_read_lock();
214 lttng_ust_liburcu_bp_rcu_read_unlock();
216 uatomic_set(&tracepoint_v1_api_used
, 1);
220 /* coverity[+alloc] */
221 static void *allocate_probes(int count
)
223 struct tp_probes
*p
=
224 zmalloc(count
* sizeof(struct lttng_ust_tracepoint_probe
)
225 + sizeof(struct tp_probes
));
226 return p
== NULL
? NULL
: p
->probes
;
229 /* coverity[+free : arg-0] */
230 static void release_probes(void *old
)
233 struct tp_probes
*tp_probes
= caa_container_of(old
,
234 struct tp_probes
, probes
[0]);
235 lttng_ust_synchronize_trace();
240 static void debug_print_probes(struct tracepoint_entry
*entry
)
244 if (!tracepoint_debug
|| !entry
->probes
)
247 for (i
= 0; entry
->probes
[i
].func
; i
++)
248 DBG("Probe %d : %p", i
, entry
->probes
[i
].func
);
252 tracepoint_entry_add_probe(struct tracepoint_entry
*entry
,
253 void (*probe
)(void), void *data
)
256 struct lttng_ust_tracepoint_probe
*old
, *new;
260 return ERR_PTR(-EINVAL
);
262 debug_print_probes(entry
);
265 /* (N -> N+1), (N != 0, 1) probes */
266 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++)
267 if (old
[nr_probes
].func
== probe
&&
268 old
[nr_probes
].data
== data
)
269 return ERR_PTR(-EEXIST
);
271 /* + 2 : one for new probe, one for NULL func */
272 new = allocate_probes(nr_probes
+ 2);
274 return ERR_PTR(-ENOMEM
);
277 nr_probes
* sizeof(struct lttng_ust_tracepoint_probe
));
278 new[nr_probes
].func
= probe
;
279 new[nr_probes
].data
= data
;
280 new[nr_probes
+ 1].func
= NULL
;
281 entry
->refcount
= nr_probes
+ 1;
283 debug_print_probes(entry
);
288 tracepoint_entry_remove_probe(struct tracepoint_entry
*entry
,
289 void (*probe
)(void), void *data
)
291 int nr_probes
= 0, nr_del
= 0, i
;
292 struct lttng_ust_tracepoint_probe
*old
, *new;
297 return ERR_PTR(-ENOENT
);
299 debug_print_probes(entry
);
300 /* (N -> M), (N > 1, M >= 0) probes */
302 for (nr_probes
= 0; old
[nr_probes
].func
; nr_probes
++) {
303 if (old
[nr_probes
].func
== probe
&&
304 old
[nr_probes
].data
== data
)
309 if (nr_probes
- nr_del
== 0) {
310 /* N -> 0, (N > 1) */
311 entry
->probes
= NULL
;
313 debug_print_probes(entry
);
317 /* N -> M, (N > 1, M > 0) */
319 new = allocate_probes(nr_probes
- nr_del
+ 1);
321 return ERR_PTR(-ENOMEM
);
322 for (i
= 0; old
[i
].func
; i
++)
323 if (old
[i
].func
!= probe
|| old
[i
].data
!= data
)
325 new[nr_probes
- nr_del
].func
= NULL
;
326 entry
->refcount
= nr_probes
- nr_del
;
329 debug_print_probes(entry
);
334 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
335 * Must be called with tracepoint mutex held.
336 * Returns NULL if not present.
338 static struct tracepoint_entry
*get_tracepoint(const char *name
)
340 struct cds_hlist_head
*head
;
341 struct cds_hlist_node
*node
;
342 struct tracepoint_entry
*e
;
343 size_t name_len
= strlen(name
);
346 if (name_len
> LTTNG_UST_SYM_NAME_LEN
- 1) {
347 WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name
, LTTNG_UST_SYM_NAME_LEN
- 1);
348 name_len
= LTTNG_UST_SYM_NAME_LEN
- 1;
350 hash
= jhash(name
, name_len
, 0);
351 head
= &tracepoint_table
[hash
& (TRACEPOINT_TABLE_SIZE
- 1)];
352 cds_hlist_for_each_entry(e
, node
, head
, hlist
) {
353 if (!strncmp(name
, e
->name
, LTTNG_UST_SYM_NAME_LEN
- 1))
360 * Add the tracepoint to the tracepoint hash table. Must be called with
361 * tracepoint mutex held.
363 static struct tracepoint_entry
*add_tracepoint(const char *name
,
364 const char *signature
)
366 struct cds_hlist_head
*head
;
367 struct cds_hlist_node
*node
;
368 struct tracepoint_entry
*e
;
369 size_t name_len
= strlen(name
);
370 size_t sig_len
= strlen(signature
);
371 size_t sig_off
, name_off
;
374 if (name_len
> LTTNG_UST_SYM_NAME_LEN
- 1) {
375 WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name
, LTTNG_UST_SYM_NAME_LEN
- 1);
376 name_len
= LTTNG_UST_SYM_NAME_LEN
- 1;
378 hash
= jhash(name
, name_len
, 0);
379 head
= &tracepoint_table
[hash
& (TRACEPOINT_TABLE_SIZE
- 1)];
380 cds_hlist_for_each_entry(e
, node
, head
, hlist
) {
381 if (!strncmp(name
, e
->name
, LTTNG_UST_SYM_NAME_LEN
- 1)) {
382 DBG("tracepoint %s busy", name
);
383 return ERR_PTR(-EEXIST
); /* Already there */
388 * Using zmalloc here to allocate a variable length elements: name and
389 * signature. Could cause some memory fragmentation if overused.
391 name_off
= sizeof(struct tracepoint_entry
);
392 sig_off
= name_off
+ name_len
+ 1;
394 e
= zmalloc(sizeof(struct tracepoint_entry
) + name_len
+ 1 + sig_len
+ 1);
396 return ERR_PTR(-ENOMEM
);
397 e
->name
= (char *) e
+ name_off
;
398 memcpy(e
->name
, name
, name_len
+ 1);
399 e
->name
[name_len
] = '\0';
401 e
->signature
= (char *) e
+ sig_off
;
402 memcpy(e
->signature
, signature
, sig_len
+ 1);
403 e
->signature
[sig_len
] = '\0';
407 e
->callsite_refcount
= 0;
409 cds_hlist_add_head(&e
->hlist
, head
);
414 * Remove the tracepoint from the tracepoint hash table. Must be called with
415 * tracepoint mutex held.
417 static void remove_tracepoint(struct tracepoint_entry
*e
)
419 cds_hlist_del(&e
->hlist
);
424 * Sets the probe callback corresponding to one tracepoint.
426 static void set_tracepoint(struct tracepoint_entry
**entry
,
427 struct lttng_ust_tracepoint
*elem
, int active
)
429 WARN_ON(strncmp((*entry
)->name
, elem
->name
, LTTNG_UST_SYM_NAME_LEN
- 1) != 0);
431 * Check that signatures match before connecting a probe to a
432 * tracepoint. Warn the user if they don't.
434 if (strcmp(elem
->signature
, (*entry
)->signature
) != 0) {
435 static int warned
= 0;
437 /* Only print once, don't flood console. */
439 WARN("Tracepoint signature mismatch, not enabling one or more tracepoints. Ensure that the tracepoint probes prototypes match the application.");
440 WARN("Tracepoint \"%s\" signatures: call: \"%s\" vs probe: \"%s\".",
441 elem
->name
, elem
->signature
, (*entry
)->signature
);
444 /* Don't accept connecting non-matching signatures. */
449 * rcu_assign_pointer has a cmm_smp_wmb() which makes sure that the new
450 * probe callbacks array is consistent before setting a pointer to it.
451 * This array is referenced by __DO_TRACE from
452 * include/linux/tracepoints.h. A matching cmm_smp_read_barrier_depends()
455 lttng_ust_rcu_assign_pointer(elem
->probes
, (*entry
)->probes
);
456 CMM_STORE_SHARED(elem
->state
, active
);
460 * Disable a tracepoint and its probe callback.
461 * Note: only waiting an RCU period after setting elem->call to the empty
462 * function insures that the original callback is not used anymore. This insured
463 * by preempt_disable around the call site.
465 static void disable_tracepoint(struct lttng_ust_tracepoint
*elem
)
467 CMM_STORE_SHARED(elem
->state
, 0);
468 lttng_ust_rcu_assign_pointer(elem
->probes
, NULL
);
472 * Add the callsite to the callsite hash table. Must be called with
473 * tracepoint mutex held.
475 static void add_callsite(struct tracepoint_lib
* lib
, struct lttng_ust_tracepoint
*tp
)
477 struct cds_hlist_head
*head
;
478 struct callsite_entry
*e
;
479 const char *name
= tp
->name
;
480 size_t name_len
= strlen(name
);
482 struct tracepoint_entry
*tp_entry
;
484 if (name_len
> LTTNG_UST_SYM_NAME_LEN
- 1) {
485 WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name
, LTTNG_UST_SYM_NAME_LEN
- 1);
486 name_len
= LTTNG_UST_SYM_NAME_LEN
- 1;
488 hash
= jhash(name
, name_len
, 0);
489 head
= &callsite_table
[hash
& (CALLSITE_TABLE_SIZE
- 1)];
490 e
= zmalloc(sizeof(struct callsite_entry
));
492 PERROR("Unable to add callsite for tracepoint \"%s\"", name
);
495 cds_hlist_add_head(&e
->hlist
, head
);
497 cds_list_add(&e
->node
, &lib
->callsites
);
499 tp_entry
= get_tracepoint(name
);
502 tp_entry
->callsite_refcount
++;
503 e
->tp_entry_callsite_ref
= true;
507 * Remove the callsite from the callsite hash table and from lib
508 * callsite list. Must be called with tracepoint mutex held.
510 static void remove_callsite(struct callsite_entry
*e
)
512 struct tracepoint_entry
*tp_entry
;
514 tp_entry
= get_tracepoint(e
->tp
->name
);
516 if (e
->tp_entry_callsite_ref
)
517 tp_entry
->callsite_refcount
--;
518 if (tp_entry
->callsite_refcount
== 0)
519 disable_tracepoint(e
->tp
);
521 cds_hlist_del(&e
->hlist
);
522 cds_list_del(&e
->node
);
527 * Enable/disable all callsites based on the state of a specific
529 * Must be called with tracepoint mutex held.
531 static void tracepoint_sync_callsites(const char *name
)
533 struct cds_hlist_head
*head
;
534 struct cds_hlist_node
*node
;
535 struct callsite_entry
*e
;
536 size_t name_len
= strlen(name
);
538 struct tracepoint_entry
*tp_entry
;
540 tp_entry
= get_tracepoint(name
);
541 if (name_len
> LTTNG_UST_SYM_NAME_LEN
- 1) {
542 WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name
, LTTNG_UST_SYM_NAME_LEN
- 1);
543 name_len
= LTTNG_UST_SYM_NAME_LEN
- 1;
545 hash
= jhash(name
, name_len
, 0);
546 head
= &callsite_table
[hash
& (CALLSITE_TABLE_SIZE
- 1)];
547 cds_hlist_for_each_entry(e
, node
, head
, hlist
) {
548 struct lttng_ust_tracepoint
*tp
= e
->tp
;
550 if (strncmp(name
, tp
->name
, LTTNG_UST_SYM_NAME_LEN
- 1))
553 if (!e
->tp_entry_callsite_ref
) {
554 tp_entry
->callsite_refcount
++;
555 e
->tp_entry_callsite_ref
= true;
557 set_tracepoint(&tp_entry
, tp
,
558 !!tp_entry
->refcount
);
560 disable_tracepoint(tp
);
561 e
->tp_entry_callsite_ref
= false;
567 * tracepoint_update_probe_range - Update a probe range
568 * @begin: beginning of the range
569 * @end: end of the range
571 * Updates the probe callback corresponding to a range of tracepoints.
574 void tracepoint_update_probe_range(struct lttng_ust_tracepoint
* const *begin
,
575 struct lttng_ust_tracepoint
* const *end
)
577 struct lttng_ust_tracepoint
* const *iter
;
578 struct tracepoint_entry
*mark_entry
;
580 for (iter
= begin
; iter
< end
; iter
++) {
582 continue; /* skip dummy */
583 if (!(*iter
)->name
) {
584 disable_tracepoint(*iter
);
587 mark_entry
= get_tracepoint((*iter
)->name
);
589 set_tracepoint(&mark_entry
, *iter
,
590 !!mark_entry
->refcount
);
592 disable_tracepoint(*iter
);
597 static void lib_update_tracepoints(struct tracepoint_lib
*lib
)
599 tracepoint_update_probe_range(lib
->tracepoints_start
,
600 lib
->tracepoints_start
+ lib
->tracepoints_count
);
603 static void lib_register_callsites(struct tracepoint_lib
*lib
)
605 struct lttng_ust_tracepoint
* const *begin
;
606 struct lttng_ust_tracepoint
* const *end
;
607 struct lttng_ust_tracepoint
* const *iter
;
609 begin
= lib
->tracepoints_start
;
610 end
= lib
->tracepoints_start
+ lib
->tracepoints_count
;
612 for (iter
= begin
; iter
< end
; iter
++) {
614 continue; /* skip dummy */
615 if (!(*iter
)->name
) {
618 add_callsite(lib
, *iter
);
622 static void lib_unregister_callsites(struct tracepoint_lib
*lib
)
624 struct callsite_entry
*callsite
, *tmp
;
626 cds_list_for_each_entry_safe(callsite
, tmp
, &lib
->callsites
, node
)
627 remove_callsite(callsite
);
631 * Update probes, removing the faulty probes.
633 static void tracepoint_update_probes(void)
635 struct tracepoint_lib
*lib
;
637 /* tracepoints registered from libraries and executable. */
638 cds_list_for_each_entry(lib
, &libs
, list
)
639 lib_update_tracepoints(lib
);
642 static struct lttng_ust_tracepoint_probe
*
643 tracepoint_add_probe(const char *name
, void (*probe
)(void), void *data
,
644 const char *signature
)
646 struct tracepoint_entry
*entry
;
647 struct lttng_ust_tracepoint_probe
*old
;
649 entry
= get_tracepoint(name
);
651 if (strcmp(entry
->signature
, signature
) != 0) {
652 ERR("Tracepoint and probe signature do not match.");
653 return ERR_PTR(-EINVAL
);
656 entry
= add_tracepoint(name
, signature
);
658 return (struct lttng_ust_tracepoint_probe
*)entry
;
660 old
= tracepoint_entry_add_probe(entry
, probe
, data
);
661 if (IS_ERR(old
) && !entry
->refcount
)
662 remove_tracepoint(entry
);
666 static void tracepoint_release_queue_add_old_probes(void *old
)
668 release_queue_need_update
= 1;
670 struct tp_probes
*tp_probes
= caa_container_of(old
,
671 struct tp_probes
, probes
[0]);
672 cds_list_add(&tp_probes
->u
.list
, &release_queue
);
677 * __tracepoint_probe_register - Connect a probe to a tracepoint
678 * @name: tracepoint name
679 * @probe: probe handler
681 * Returns 0 if ok, error value on error.
682 * The probe address must at least be aligned on the architecture pointer size.
683 * Called with the tracepoint mutex held.
685 int __tracepoint_probe_register(const char *name
, void (*probe
)(void),
686 void *data
, const char *signature
)
691 DBG("Registering probe to tracepoint %s", name
);
693 pthread_mutex_lock(&tracepoint_mutex
);
694 old
= tracepoint_add_probe(name
, probe
, data
, signature
);
700 tracepoint_sync_callsites(name
);
703 pthread_mutex_unlock(&tracepoint_mutex
);
708 * Caller needs to invoke __tracepoint_probe_release_queue() after
709 * calling __tracepoint_probe_register_queue_release() one or multiple
710 * times to ensure it does not leak memory.
712 int __tracepoint_probe_register_queue_release(const char *name
,
713 void (*probe
)(void), void *data
, const char *signature
)
718 DBG("Registering probe to tracepoint %s. Queuing release.", name
);
720 pthread_mutex_lock(&tracepoint_mutex
);
721 old
= tracepoint_add_probe(name
, probe
, data
, signature
);
727 tracepoint_sync_callsites(name
);
728 tracepoint_release_queue_add_old_probes(old
);
730 pthread_mutex_unlock(&tracepoint_mutex
);
734 static void *tracepoint_remove_probe(const char *name
, void (*probe
)(void),
737 struct tracepoint_entry
*entry
;
740 entry
= get_tracepoint(name
);
742 return ERR_PTR(-ENOENT
);
743 old
= tracepoint_entry_remove_probe(entry
, probe
, data
);
746 if (!entry
->refcount
)
747 remove_tracepoint(entry
);
752 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
753 * @name: tracepoint name
754 * @probe: probe function pointer
755 * @probe: probe data pointer
757 int __tracepoint_probe_unregister(const char *name
, void (*probe
)(void),
763 DBG("Un-registering probe from tracepoint %s", name
);
765 pthread_mutex_lock(&tracepoint_mutex
);
766 old
= tracepoint_remove_probe(name
, probe
, data
);
771 tracepoint_sync_callsites(name
);
774 pthread_mutex_unlock(&tracepoint_mutex
);
779 * Caller needs to invoke __tracepoint_probe_release_queue() after
780 * calling __tracepoint_probe_unregister_queue_release() one or multiple
781 * times to ensure it does not leak memory.
783 int __tracepoint_probe_unregister_queue_release(const char *name
,
784 void (*probe
)(void), void *data
)
789 DBG("Un-registering probe from tracepoint %s. Queuing release.", name
);
791 pthread_mutex_lock(&tracepoint_mutex
);
792 old
= tracepoint_remove_probe(name
, probe
, data
);
797 tracepoint_sync_callsites(name
);
798 tracepoint_release_queue_add_old_probes(old
);
800 pthread_mutex_unlock(&tracepoint_mutex
);
804 void __tracepoint_probe_prune_release_queue(void)
806 CDS_LIST_HEAD(release_probes
);
807 struct tp_probes
*pos
, *next
;
809 DBG("Release queue of unregistered tracepoint probes.");
811 pthread_mutex_lock(&tracepoint_mutex
);
812 if (!release_queue_need_update
)
814 if (!cds_list_empty(&release_queue
))
815 cds_list_replace_init(&release_queue
, &release_probes
);
816 release_queue_need_update
= 0;
818 /* Wait for grace period between all sync_callsites and free. */
819 lttng_ust_synchronize_trace();
821 cds_list_for_each_entry_safe(pos
, next
, &release_probes
, u
.list
) {
822 cds_list_del(&pos
->u
.list
);
826 pthread_mutex_unlock(&tracepoint_mutex
);
829 static void tracepoint_add_old_probes(void *old
)
833 struct tp_probes
*tp_probes
= caa_container_of(old
,
834 struct tp_probes
, probes
[0]);
835 cds_list_add(&tp_probes
->u
.list
, &old_probes
);
840 * tracepoint_probe_register_noupdate - register a probe but not connect
841 * @name: tracepoint name
842 * @probe: probe handler
844 * caller must call tracepoint_probe_update_all()
846 int tracepoint_probe_register_noupdate(const char *name
, void (*probe
)(void),
847 void *data
, const char *signature
)
852 pthread_mutex_lock(&tracepoint_mutex
);
853 old
= tracepoint_add_probe(name
, probe
, data
, signature
);
858 tracepoint_add_old_probes(old
);
860 pthread_mutex_unlock(&tracepoint_mutex
);
865 * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
866 * @name: tracepoint name
867 * @probe: probe function pointer
869 * caller must call tracepoint_probe_update_all()
870 * Called with the tracepoint mutex held.
872 int tracepoint_probe_unregister_noupdate(const char *name
, void (*probe
)(void),
878 DBG("Un-registering probe from tracepoint %s", name
);
880 pthread_mutex_lock(&tracepoint_mutex
);
881 old
= tracepoint_remove_probe(name
, probe
, data
);
886 tracepoint_add_old_probes(old
);
888 pthread_mutex_unlock(&tracepoint_mutex
);
893 * tracepoint_probe_update_all - update tracepoints
895 void tracepoint_probe_update_all(void)
897 CDS_LIST_HEAD(release_probes
);
898 struct tp_probes
*pos
, *next
;
900 pthread_mutex_lock(&tracepoint_mutex
);
904 if (!cds_list_empty(&old_probes
))
905 cds_list_replace_init(&old_probes
, &release_probes
);
908 tracepoint_update_probes();
909 /* Wait for grace period between update_probes and free. */
910 lttng_ust_synchronize_trace();
911 cds_list_for_each_entry_safe(pos
, next
, &release_probes
, u
.list
) {
912 cds_list_del(&pos
->u
.list
);
916 pthread_mutex_unlock(&tracepoint_mutex
);
919 void tracepoint_set_new_tracepoint_cb(void (*cb
)(struct lttng_ust_tracepoint
*))
921 new_tracepoint_cb
= cb
;
924 static void new_tracepoints(struct lttng_ust_tracepoint
* const *start
,
925 struct lttng_ust_tracepoint
* const *end
)
927 if (new_tracepoint_cb
) {
928 struct lttng_ust_tracepoint
* const *t
;
930 for (t
= start
; t
< end
; t
++) {
932 new_tracepoint_cb(*t
);
938 * tracepoint_{un,}register_lib is meant to be looked up by instrumented
939 * applications through dlsym(). If found, those can register their
940 * tracepoints, else those tracepoints will not be available for
941 * tracing. The number at the end of those symbols acts as a major
942 * version for tracepoints.
944 * Older instrumented applications should still work with newer
945 * liblttng-ust, but it is fine that instrumented applications compiled
946 * against recent liblttng-ust headers require a recent liblttng-ust
947 * runtime for those tracepoints to be taken into account.
949 int tracepoint_register_lib2(struct lttng_ust_tracepoint
* const *tracepoints_start
,
950 int tracepoints_count
)
952 struct tracepoint_lib
*pl
, *iter
;
956 pl
= (struct tracepoint_lib
*) zmalloc(sizeof(struct tracepoint_lib
));
958 PERROR("Unable to register tracepoint lib");
961 pl
->tracepoints_start
= tracepoints_start
;
962 pl
->tracepoints_count
= tracepoints_count
;
963 CDS_INIT_LIST_HEAD(&pl
->callsites
);
965 pthread_mutex_lock(&tracepoint_mutex
);
967 * We sort the libs by struct lib pointer address.
969 cds_list_for_each_entry_reverse(iter
, &libs
, list
) {
970 BUG_ON(iter
== pl
); /* Should never be in the list twice */
972 /* We belong to the location right after iter. */
973 cds_list_add(&pl
->list
, &iter
->list
);
977 /* We should be added at the head of the list */
978 cds_list_add(&pl
->list
, &libs
);
980 new_tracepoints(tracepoints_start
, tracepoints_start
+ tracepoints_count
);
981 lib_register_callsites(pl
);
982 lib_update_tracepoints(pl
);
983 pthread_mutex_unlock(&tracepoint_mutex
);
985 DBG("just registered a tracepoints section from %p and having %d tracepoints",
986 tracepoints_start
, tracepoints_count
);
990 for (i
= 0; i
< tracepoints_count
; i
++) {
991 DBG("registered tracepoint: %s", tracepoints_start
[i
]->name
);
998 /* Exposed for backward compatibility with old instrumented applications. */
999 int tracepoint_register_lib(struct lttng_ust_tracepoint
* const *tracepoints_start
,
1000 int tracepoints_count
)
1002 lttng_ust_tracepoint_set_v1_used();
1003 return tracepoint_register_lib2(tracepoints_start
, tracepoints_count
);
1006 int tracepoint_unregister_lib2(struct lttng_ust_tracepoint
* const *tracepoints_start
)
1008 struct tracepoint_lib
*lib
;
1010 pthread_mutex_lock(&tracepoint_mutex
);
1011 cds_list_for_each_entry(lib
, &libs
, list
) {
1012 if (lib
->tracepoints_start
!= tracepoints_start
)
1015 cds_list_del(&lib
->list
);
1017 * Unregistering a callsite also decreases the
1018 * callsite reference count of the corresponding
1019 * tracepoint, and disables the tracepoint if
1020 * the reference count drops to zero.
1022 lib_unregister_callsites(lib
);
1023 DBG("just unregistered a tracepoints section from %p",
1024 lib
->tracepoints_start
);
1028 pthread_mutex_unlock(&tracepoint_mutex
);
1032 /* Exposed for backward compatibility with old instrumented applications. */
1033 int tracepoint_unregister_lib(struct lttng_ust_tracepoint
* const *tracepoints_start
)
1035 lttng_ust_tracepoint_set_v1_used();
1036 return tracepoint_unregister_lib2(tracepoints_start
);
1040 * Report in debug message whether the compiler correctly supports weak
1041 * hidden symbols. This test checks that the address associated with two
1042 * weak symbols with hidden visibility is the same when declared within
1043 * two compile units part of the same module.
1045 static void check_weak_hidden(void)
1047 DBG("Your compiler treats weak symbols with hidden visibility for integer objects as %s between compile units part of the same module.",
1048 &__tracepoint_test_symbol1
== lttng_ust_tp_check_weak_hidden1() ?
1050 "DIFFERENT addresses");
1051 DBG("Your compiler treats weak symbols with hidden visibility for pointer objects as %s between compile units part of the same module.",
1052 &__tracepoint_test_symbol2
== lttng_ust_tp_check_weak_hidden2() ?
1054 "DIFFERENT addresses");
1055 DBG("Your compiler treats weak symbols with hidden visibility for 24-byte structure objects as %s between compile units part of the same module.",
1056 &__tracepoint_test_symbol3
== lttng_ust_tp_check_weak_hidden3() ?
1058 "DIFFERENT addresses");
1061 void init_tracepoint(void)
1063 if (uatomic_xchg(&initialized
, 1) == 1)
1066 check_weak_hidden();
1069 void exit_tracepoint(void)
1075 * Create the wrapper symbols.
1077 #undef tp_rcu_read_lock
1078 #undef tp_rcu_read_unlock
1079 #undef tp_rcu_dereference
1081 void tp_rcu_read_lock(void)
1083 lttng_ust_urcu_read_lock();
1086 void tp_rcu_read_unlock(void)
1088 lttng_ust_urcu_read_unlock();
1091 void *tp_rcu_dereference_sym(void *p
)
1093 return lttng_ust_rcu_dereference(p
);
1097 * Programs that have threads that survive after they exit, and therefore call
1098 * library destructors, should disable the tracepoint destructors by calling
1099 * tp_disable_destructors(). This will leak the tracepoint
1100 * instrumentation library shared object, leaving its teardown to the operating
1101 * system process teardown.
1103 * To access and/or modify this value, users need to use a combination of
1104 * dlopen(3) and dlsym(3) to get an handle on the
1105 * tp_disable_destructors and tp_get_destructors_state symbols below.
1107 void tp_disable_destructors(void)
1109 uatomic_set(&tracepoint_destructors_state
, 0);
1113 * Returns 1 if the destructors are enabled and should be executed.
1114 * Returns 0 if the destructors are disabled.
1116 int tp_get_destructors_state(void)
1118 return uatomic_read(&tracepoint_destructors_state
);
1121 void lttng_ust_synchronize_trace(void)
1123 lttng_ust_urcu_synchronize_rcu();
1125 * For legacy tracepoint instrumentation, also wait for urcu-bp
1128 if (lttng_ust_liburcu_bp_synchronize_rcu
)
1129 lttng_ust_liburcu_bp_synchronize_rcu();
1133 * Create the wrapper symbols for legacy v1 API.
1135 void tp_rcu_read_lock_bp(void)
1137 lttng_ust_urcu_read_lock();
1140 void tp_rcu_read_unlock_bp(void)
1142 lttng_ust_urcu_read_unlock();
1145 void *tp_rcu_dereference_sym_bp(void *p
)
1147 return lttng_ust_rcu_dereference(p
);