X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=liblttng-ust%2Ftracepoint.c;h=cf7cf63c992d16e90647aa5856d82059bf05c2db;hb=9560f5ebf55ec70baefe6da3e3d644fc7d497b63;hp=14b8231f879fca9d3aa8e3bde5a6a661cbb6b4c2;hpb=baa1e0bcf6630bd3f9282b82586d1a730f3d7ae2;p=lttng-ust.git diff --git a/liblttng-ust/tracepoint.c b/liblttng-ust/tracepoint.c index 14b8231f..cf7cf63c 100644 --- a/liblttng-ust/tracepoint.c +++ b/liblttng-ust/tracepoint.c @@ -26,7 +26,7 @@ #include #include -#include +#include #include #include #include @@ -53,6 +53,22 @@ 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; + +/* + * Expose the now deprecated symbol __tracepoints__disable_destructors for + * backward compatibility of applications built against old versions of + * lttng-ust. We need to keep __tracepoints__disable_destructors up to date + * within the new destructor disabling API because old applications read this + * symbol directly. + */ +int __tracepoints__disable_destructors __attribute__((weak)); + static void (*new_tracepoint_cb)(struct lttng_ust_tracepoint *); /* @@ -107,8 +123,8 @@ struct tracepoint_entry { struct lttng_ust_tracepoint_probe *probes; int refcount; /* Number of times armed. 0 if disarmed. */ int callsite_refcount; /* how many libs use this tracepoint */ - const char *signature; - char name[0]; + char *signature; + char *name; }; struct tp_probes { @@ -132,8 +148,75 @@ struct callsite_entry { struct cds_hlist_node hlist; /* hash table node */ struct cds_list_head node; /* lib list of callsites node */ struct lttng_ust_tracepoint *tp; + bool tp_entry_callsite_ref; /* Has a tp_entry took a ref on this callsite */ }; +static int tracepoint_v1_api_used; +static void (*lttng_ust_liburcu_bp_synchronize_rcu)(void); +static void (*lttng_ust_liburcu_bp_rcu_read_lock)(void); +static void (*lttng_ust_liburcu_bp_rcu_read_unlock)(void); +void (*lttng_ust_liburcu_bp_before_fork)(void); +void (*lttng_ust_liburcu_bp_after_fork_parent)(void); +void (*lttng_ust_liburcu_bp_after_fork_child)(void); + +static bool lttng_ust_tracepoint_v1_used(void) +{ + return uatomic_read(&tracepoint_v1_api_used); +} + +static void lttng_ust_tracepoint_set_v1_used(void) +{ + if (!lttng_ust_tracepoint_v1_used()) { + /* + * Perform dlsym here rather than lazily on first use to + * eliminate nesting of dynamic loader lock (used within + * dlsym) inside the ust lock. + */ + if (!lttng_ust_liburcu_bp_synchronize_rcu) { + lttng_ust_liburcu_bp_synchronize_rcu = URCU_FORCE_CAST(void (*)(void), + dlsym(RTLD_DEFAULT, "synchronize_rcu_bp")); + if (!lttng_ust_liburcu_bp_synchronize_rcu) + abort(); + } + if (!lttng_ust_liburcu_bp_before_fork) { + lttng_ust_liburcu_bp_before_fork = URCU_FORCE_CAST(void (*)(void), + dlsym(RTLD_DEFAULT, "rcu_bp_before_fork")); + if (!lttng_ust_liburcu_bp_before_fork) + abort(); + } + if (!lttng_ust_liburcu_bp_after_fork_parent) { + lttng_ust_liburcu_bp_after_fork_parent = URCU_FORCE_CAST(void (*)(void), + dlsym(RTLD_DEFAULT, "rcu_bp_after_fork_parent")); + if (!lttng_ust_liburcu_bp_after_fork_parent) + abort(); + } + if (!lttng_ust_liburcu_bp_after_fork_child) { + lttng_ust_liburcu_bp_after_fork_child = URCU_FORCE_CAST(void (*)(void), + dlsym(RTLD_DEFAULT, "rcu_bp_after_fork_child")); + if (!lttng_ust_liburcu_bp_after_fork_child) + abort(); + } + if (!lttng_ust_liburcu_bp_rcu_read_lock) { + lttng_ust_liburcu_bp_rcu_read_lock = URCU_FORCE_CAST(void (*)(void), + dlsym(RTLD_DEFAULT, "rcu_read_lock_bp")); + if (!lttng_ust_liburcu_bp_rcu_read_lock) + abort(); + } + if (!lttng_ust_liburcu_bp_rcu_read_unlock) { + lttng_ust_liburcu_bp_rcu_read_unlock = URCU_FORCE_CAST(void (*)(void), + dlsym(RTLD_DEFAULT, "rcu_read_unlock_bp")); + if (!lttng_ust_liburcu_bp_rcu_read_unlock) + abort(); + } + + /* Fixup URCU bp TLS. */ + lttng_ust_liburcu_bp_rcu_read_lock(); + lttng_ust_liburcu_bp_rcu_read_unlock(); + + uatomic_set(&tracepoint_v1_api_used, 1); + } +} + /* coverity[+alloc] */ static void *allocate_probes(int count) { @@ -149,7 +232,7 @@ 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); } } @@ -284,6 +367,8 @@ static struct tracepoint_entry *add_tracepoint(const char *name, struct cds_hlist_node *node; struct tracepoint_entry *e; size_t name_len = strlen(name); + size_t sig_len = strlen(signature); + size_t sig_off, name_off; uint32_t hash; if (name_len > LTTNG_UST_SYM_NAME_LEN - 1) { @@ -298,19 +383,29 @@ static struct tracepoint_entry *add_tracepoint(const char *name, return ERR_PTR(-EEXIST); /* Already there */ } } + /* - * Using zmalloc here to allocate a variable length element. Could - * cause some memory fragmentation if overused. + * Using zmalloc here to allocate a variable length elements: name and + * signature. Could cause some memory fragmentation if overused. */ - e = zmalloc(sizeof(struct tracepoint_entry) + name_len + 1); + name_off = sizeof(struct tracepoint_entry); + sig_off = name_off + name_len + 1; + + e = zmalloc(sizeof(struct tracepoint_entry) + name_len + 1 + sig_len + 1); if (!e) return ERR_PTR(-ENOMEM); - memcpy(&e->name[0], name, name_len + 1); + e->name = (char *) e + name_off; + memcpy(e->name, name, name_len + 1); e->name[name_len] = '\0'; + + e->signature = (char *) e + sig_off; + memcpy(e->signature, signature, sig_len + 1); + e->signature[sig_len] = '\0'; + e->probes = NULL; e->refcount = 0; e->callsite_refcount = 0; - e->signature = signature; + cds_hlist_add_head(&e->hlist, head); return e; } @@ -357,7 +452,7 @@ 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); } @@ -370,7 +465,7 @@ 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); } /* @@ -405,6 +500,7 @@ static void add_callsite(struct tracepoint_lib * lib, struct lttng_ust_tracepoin if (!tp_entry) return; tp_entry->callsite_refcount++; + e->tp_entry_callsite_ref = true; } /* @@ -417,7 +513,8 @@ static void remove_callsite(struct callsite_entry *e) tp_entry = get_tracepoint(e->tp->name); if (tp_entry) { - tp_entry->callsite_refcount--; + if (e->tp_entry_callsite_ref) + tp_entry->callsite_refcount--; if (tp_entry->callsite_refcount == 0) disable_tracepoint(e->tp); } @@ -453,10 +550,15 @@ static void tracepoint_sync_callsites(const char *name) if (strncmp(name, tp->name, LTTNG_UST_SYM_NAME_LEN - 1)) continue; if (tp_entry) { + if (!e->tp_entry_callsite_ref) { + tp_entry->callsite_refcount++; + e->tp_entry_callsite_ref = true; + } set_tracepoint(&tp_entry, tp, !!tp_entry->refcount); } else { disable_tracepoint(tp); + e->tp_entry_callsite_ref = false; } } } @@ -545,7 +647,12 @@ tracepoint_add_probe(const char *name, void (*probe)(void), void *data, struct lttng_ust_tracepoint_probe *old; entry = get_tracepoint(name); - if (!entry) { + if (entry) { + if (strcmp(entry->signature, signature) != 0) { + ERR("Tracepoint and probe signature do not match."); + return ERR_PTR(-EINVAL); + } + } else { entry = add_tracepoint(name, signature); if (IS_ERR(entry)) return (struct lttng_ust_tracepoint_probe *)entry; @@ -709,7 +816,7 @@ 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); @@ -800,7 +907,7 @@ 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); @@ -827,8 +934,20 @@ static void new_tracepoints(struct lttng_ust_tracepoint * const *start, } } -int tracepoint_register_lib(struct lttng_ust_tracepoint * const *tracepoints_start, - int tracepoints_count) +/* + * 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_lib2(struct lttng_ust_tracepoint * const *tracepoints_start, + int tracepoints_count) { struct tracepoint_lib *pl, *iter; @@ -876,7 +995,15 @@ lib_added: return 0; } -int tracepoint_unregister_lib(struct lttng_ust_tracepoint * const *tracepoints_start) +/* Exposed for backward compatibility with old instrumented applications. */ +int tracepoint_register_lib(struct lttng_ust_tracepoint * const *tracepoints_start, + int tracepoints_count) +{ + lttng_ust_tracepoint_set_v1_used(); + return tracepoint_register_lib2(tracepoints_start, tracepoints_count); +} + +int tracepoint_unregister_lib2(struct lttng_ust_tracepoint * const *tracepoints_start) { struct tracepoint_lib *lib; @@ -902,6 +1029,13 @@ int tracepoint_unregister_lib(struct lttng_ust_tracepoint * const *tracepoints_s return 0; } +/* Exposed for backward compatibility with old instrumented applications. */ +int tracepoint_unregister_lib(struct lttng_ust_tracepoint * const *tracepoints_start) +{ + lttng_ust_tracepoint_set_v1_used(); + return tracepoint_unregister_lib2(tracepoints_start); +} + /* * Report in debug message whether the compiler correctly supports weak * hidden symbols. This test checks that the address associated with two @@ -940,21 +1074,75 @@ 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(void) +{ + lttng_ust_urcu_read_lock(); +} + +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) +{ + return uatomic_read(&tracepoint_destructors_state); +} +void lttng_ust_synchronize_trace(void) +{ + lttng_ust_urcu_synchronize_rcu(); + /* + * For legacy tracepoint instrumentation, also wait for urcu-bp + * grace period. + */ + if (lttng_ust_liburcu_bp_synchronize_rcu) + lttng_ust_liburcu_bp_synchronize_rcu(); +} + +/* + * Create the wrapper symbols for legacy v1 API. + */ void tp_rcu_read_lock_bp(void) { - rcu_read_lock_bp(); + lttng_ust_urcu_read_lock(); } void tp_rcu_read_unlock_bp(void) { - rcu_read_unlock_bp(); + lttng_ust_urcu_read_unlock(); } void *tp_rcu_dereference_sym_bp(void *p) { - return rcu_dereference_bp(p); + return lttng_ust_rcu_dereference(p); }