X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust%2Ftracepoint.c;h=f65097f6aaa92cc640eab93751847d32abf9556d;hb=c0c0989ab70574e09b2f7e8b48c2da6af664a849;hp=2c25d46250b603c6ed3e5c987f24aae905ef482a;hpb=2c05c691a10f3130f9339a15369140ad6ca70f85;p=lttng-ust.git diff --git a/liblttng-ust/tracepoint.c b/liblttng-ust/tracepoint.c index 2c25d462..f65097f6 100644 --- a/liblttng-ust/tracepoint.c +++ b/liblttng-ust/tracepoint.c @@ -1,21 +1,9 @@ /* + * SPDX-License-Identifier: LGPL-2.1-only + * * Copyright (C) 2008-2011 Mathieu Desnoyers * Copyright (C) 2009 Pierre-Marc Fournier * - * This library is free software; you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public - * License as published by the Free Software Foundation; - * version 2.1 of the License. - * - * This library is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - * Lesser General Public License for more details. - * - * You should have received a copy of the GNU Lesser General Public - * License along with this library; if not, write to the Free Software - * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA - * * Ported to userspace by Pierre-Marc Fournier. */ @@ -26,7 +14,7 @@ #include #include -#include +#include #include #include #include @@ -53,6 +41,13 @@ struct { /* Set to 1 to enable tracepoint debug output */ static const int tracepoint_debug; static int initialized; + +/* + * If tracepoint_destructors_state = 1, tracepoint destructors are + * enabled. They are disabled otherwise. + */ +static int tracepoint_destructors_state = 1; + static void (*new_tracepoint_cb)(struct lttng_ust_tracepoint *); /* @@ -150,7 +145,7 @@ static void release_probes(void *old) if (old) { struct tp_probes *tp_probes = caa_container_of(old, struct tp_probes, probes[0]); - synchronize_rcu(); + lttng_ust_synchronize_trace(); free(tp_probes); } } @@ -370,7 +365,7 @@ static void set_tracepoint(struct tracepoint_entry **entry, * include/linux/tracepoints.h. A matching cmm_smp_read_barrier_depends() * is used. */ - rcu_assign_pointer(elem->probes, (*entry)->probes); + lttng_ust_rcu_assign_pointer(elem->probes, (*entry)->probes); CMM_STORE_SHARED(elem->state, active); } @@ -383,7 +378,7 @@ static void set_tracepoint(struct tracepoint_entry **entry, static void disable_tracepoint(struct lttng_ust_tracepoint *elem) { CMM_STORE_SHARED(elem->state, 0); - rcu_assign_pointer(elem->probes, NULL); + lttng_ust_rcu_assign_pointer(elem->probes, NULL); } /* @@ -734,7 +729,7 @@ void __tracepoint_probe_prune_release_queue(void) release_queue_need_update = 0; /* Wait for grace period between all sync_callsites and free. */ - synchronize_rcu(); + lttng_ust_synchronize_trace(); cds_list_for_each_entry_safe(pos, next, &release_probes, u.list) { cds_list_del(&pos->u.list); @@ -825,7 +820,7 @@ void tracepoint_probe_update_all(void) tracepoint_update_probes(); /* Wait for grace period between update_probes and free. */ - synchronize_rcu(); + lttng_ust_synchronize_trace(); cds_list_for_each_entry_safe(pos, next, &release_probes, u.list) { cds_list_del(&pos->u.list); free(pos); @@ -852,8 +847,20 @@ static void new_tracepoints(struct lttng_ust_tracepoint * const *start, } } +/* + * tracepoint_{un,}register_lib is meant to be looked up by instrumented + * applications through dlsym(). If found, those can register their + * tracepoints, else those tracepoints will not be available for + * tracing. The number at the end of those symbols acts as a major + * version for tracepoints. + * + * Older instrumented applications should still work with newer + * liblttng-ust, but it is fine that instrumented applications compiled + * against recent liblttng-ust headers require a recent liblttng-ust + * runtime for those tracepoints to be taken into account. + */ int tracepoint_register_lib(struct lttng_ust_tracepoint * const *tracepoints_start, - int tracepoints_count) + int tracepoints_count) { struct tracepoint_lib *pl, *iter; @@ -965,21 +972,51 @@ void exit_tracepoint(void) /* * Create the wrapper symbols. */ -#undef tp_rcu_read_lock_bp -#undef tp_rcu_read_unlock_bp -#undef tp_rcu_dereference_bp +#undef tp_rcu_read_lock +#undef tp_rcu_read_unlock +#undef tp_rcu_dereference -void tp_rcu_read_lock_bp(void) +void tp_rcu_read_lock(void) { - rcu_read_lock_bp(); + lttng_ust_urcu_read_lock(); } -void tp_rcu_read_unlock_bp(void) +void tp_rcu_read_unlock(void) +{ + lttng_ust_urcu_read_unlock(); +} + +void *tp_rcu_dereference_sym(void *p) +{ + return lttng_ust_rcu_dereference(p); +} + +/* + * Programs that have threads that survive after they exit, and therefore call + * library destructors, should disable the tracepoint destructors by calling + * tp_disable_destructors(). This will leak the tracepoint + * instrumentation library shared object, leaving its teardown to the operating + * system process teardown. + * + * To access and/or modify this value, users need to use a combination of + * dlopen(3) and dlsym(3) to get an handle on the + * tp_disable_destructors and tp_get_destructors_state symbols below. + */ +void tp_disable_destructors(void) +{ + uatomic_set(&tracepoint_destructors_state, 0); +} + +/* + * Returns 1 if the destructors are enabled and should be executed. + * Returns 0 if the destructors are disabled. + */ +int tp_get_destructors_state(void) { - rcu_read_unlock_bp(); + return uatomic_read(&tracepoint_destructors_state); } -void *tp_rcu_dereference_sym_bp(void *p) +void lttng_ust_synchronize_trace(void) { - return rcu_dereference_bp(p); + lttng_ust_urcu_synchronize_rcu(); }