Move symbol preventing unloading of probe providers

[deliverable/lttng-ust.git] / include / lttng / tracepoint.h

diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h
index 39f2c4db752342f14c5bd8206174093595ebacec..d77a2fb298c40f99c7fd290eb48eda48d36bcae9 100644 (file)
--- a/include/lttng/tracepoint.h
+++ b/include/lttng/tracepoint.h
@@ -226,21 +226,6 @@ struct lttng_ust_tracepoint_dlopen {
 extern struct lttng_ust_tracepoint_dlopen tracepoint_dlopen;
 extern struct lttng_ust_tracepoint_dlopen *tracepoint_dlopen_ptr;
 
-/* Disable tracepoint destructors. */
-int __tracepoints__disable_destructors __attribute__((weak));
-
-/*
- * Programs that have threads that survive after they exit, and
- * therefore call library destructors, should disable the tracepoint
- * destructors by calling tracepoint_disable_destructors(). This will
- * leak the tracepoint instrumentation library shared object, leaving
- * its teardown to the operating system process teardown.
- */
-static inline void tracepoint_disable_destructors(void)
-{
-       __tracepoints__disable_destructors = 1;
-}
-
 /*
  * These weak symbols, the constructor, and destructor take care of
  * registering only _one_ instance of the tracepoints per shared-ojbect
@@ -265,6 +250,37 @@ struct lttng_ust_tracepoint_dlopen tracepoint_dlopen
 struct lttng_ust_tracepoint_dlopen *tracepoint_dlopen_ptr
        __attribute__((weak, visibility("hidden")));
 
+/*
+ * Tracepoint dynamic linkage handling (callbacks). Hidden visibility: shared
+ * across objects in a module/main executable. The callbacks are used to
+ * control and check if the destructors should be executed.
+ */
+struct lttng_ust_tracepoint_destructors_syms {
+       int *old_tracepoint_disable_destructors;
+       void (*tracepoint_disable_destructors)(void);
+       int (*tracepoint_get_destructors_state)(void);
+};
+
+extern struct lttng_ust_tracepoint_destructors_syms tracepoint_destructors_syms;
+extern struct lttng_ust_tracepoint_destructors_syms *tracepoint_destructors_syms_ptr;
+
+struct lttng_ust_tracepoint_destructors_syms tracepoint_destructors_syms
+       __attribute__((weak, visibility("hidden")));
+struct lttng_ust_tracepoint_destructors_syms *tracepoint_destructors_syms_ptr
+       __attribute__((weak, visibility("hidden")));
+
+static inline void tracepoint_disable_destructors(void)
+{
+       if (!tracepoint_dlopen_ptr)
+               tracepoint_dlopen_ptr = &tracepoint_dlopen;
+       if (!tracepoint_destructors_syms_ptr)
+               tracepoint_destructors_syms_ptr = &tracepoint_destructors_syms;
+       if (tracepoint_dlopen_ptr->liblttngust_handle
+                       && tracepoint_destructors_syms_ptr->tracepoint_disable_destructors)
+               tracepoint_destructors_syms_ptr->tracepoint_disable_destructors();
+       *tracepoint_destructors_syms_ptr->old_tracepoint_disable_destructors = 1;
+}
+
 #ifndef _LGPL_SOURCE
 static inline void lttng_ust_notrace
 __tracepoint__init_urcu_sym(void);
@@ -335,16 +351,43 @@ __tracepoints__destroy(void)
                return;
        if (!tracepoint_dlopen_ptr)
                tracepoint_dlopen_ptr = &tracepoint_dlopen;
-       if (!__tracepoints__disable_destructors
-                       && tracepoint_dlopen_ptr->liblttngust_handle
-                       && !__tracepoint_ptrs_registered) {
-               ret = dlclose(tracepoint_dlopen_ptr->liblttngust_handle);
-               if (ret) {
-                       fprintf(stderr, "Error (%d) in dlclose\n", ret);
-                       abort();
-               }
-               memset(tracepoint_dlopen_ptr, 0, sizeof(*tracepoint_dlopen_ptr));
+       if (!tracepoint_destructors_syms_ptr)
+               tracepoint_destructors_syms_ptr = &tracepoint_destructors_syms;
+       if (!tracepoint_dlopen_ptr->liblttngust_handle)
+               return;
+       if (__tracepoint_ptrs_registered)
+               return;
+       /*
+        * Lookup if destructors must be executed using the new method.
+        */
+       if (tracepoint_destructors_syms_ptr->tracepoint_get_destructors_state
+               && !tracepoint_destructors_syms_ptr->tracepoint_get_destructors_state()) {
+               /*
+                * The tracepoint_get_destructors_state symbol was found with
+                * dlsym but its returned value is 0 meaning that destructors
+                * must not be executed.
+                */
+               return;
+       }
+       /*
+        * Lookup if destructors must be executed using the old method.
+        */
+       if (tracepoint_destructors_syms_ptr->old_tracepoint_disable_destructors
+               && *tracepoint_destructors_syms_ptr->old_tracepoint_disable_destructors) {
+               /*
+                * The old_tracepoint_disable_destructors symbol was found with
+                * dlsym but its value is 1 meaning that destructors must not
+                * be executed.
+                */
+               return;
        }
+
+       ret = dlclose(tracepoint_dlopen_ptr->liblttngust_handle);
+       if (ret) {
+               fprintf(stderr, "Error (%d) in dlclose\n", ret);
+               abort();
+       }
+       memset(tracepoint_dlopen_ptr, 0, sizeof(*tracepoint_dlopen_ptr));
 }
 
 #ifdef TRACEPOINT_DEFINE
@@ -415,6 +458,8 @@ __tracepoints__ptrs_init(void)
                        dlopen("liblttng-ust-tracepoint.so.0", RTLD_NOW | RTLD_GLOBAL);
        if (!tracepoint_dlopen_ptr->liblttngust_handle)
                return;
+       if (!tracepoint_destructors_syms_ptr)
+               tracepoint_destructors_syms_ptr = &tracepoint_destructors_syms;
        tracepoint_dlopen_ptr->tracepoint_register_lib =
                URCU_FORCE_CAST(int (*)(struct lttng_ust_tracepoint * const *, int),
                                dlsym(tracepoint_dlopen_ptr->liblttngust_handle,
@@ -423,6 +468,18 @@ __tracepoints__ptrs_init(void)
                URCU_FORCE_CAST(int (*)(struct lttng_ust_tracepoint * const *),
                                dlsym(tracepoint_dlopen_ptr->liblttngust_handle,
                                        "tracepoint_unregister_lib"));
+       tracepoint_destructors_syms_ptr->old_tracepoint_disable_destructors =
+               URCU_FORCE_CAST(int *,
+                               dlsym(tracepoint_dlopen_ptr->liblttngust_handle,
+                                       "__tracepoints__disable_destructors"));
+       tracepoint_destructors_syms_ptr->tracepoint_disable_destructors =
+               URCU_FORCE_CAST(void (*)(void),
+                               dlsym(tracepoint_dlopen_ptr->liblttngust_handle,
+                                       "tp_disable_destructors"));
+       tracepoint_destructors_syms_ptr->tracepoint_get_destructors_state =
+               URCU_FORCE_CAST(int (*)(void),
+                               dlsym(tracepoint_dlopen_ptr->liblttngust_handle,
+                                       "tp_get_destructors_state"));
        __tracepoint__init_urcu_sym();
        if (tracepoint_dlopen_ptr->tracepoint_register_lib) {
                tracepoint_dlopen_ptr->tracepoint_register_lib(__start___tracepoints_ptrs,
@@ -442,10 +499,13 @@ __tracepoints__ptrs_destroy(void)
                return;
        if (!tracepoint_dlopen_ptr)
                tracepoint_dlopen_ptr = &tracepoint_dlopen;
+       if (!tracepoint_destructors_syms_ptr)
+               tracepoint_destructors_syms_ptr = &tracepoint_destructors_syms;
        if (tracepoint_dlopen_ptr->tracepoint_unregister_lib)
                tracepoint_dlopen_ptr->tracepoint_unregister_lib(__start___tracepoints_ptrs);
-       if (!__tracepoints__disable_destructors
-                       && tracepoint_dlopen_ptr->liblttngust_handle
+       if (tracepoint_dlopen_ptr->liblttngust_handle
+                       && tracepoint_destructors_syms_ptr->tracepoint_get_destructors_state
+                       && tracepoint_destructors_syms_ptr->tracepoint_get_destructors_state()
                        && !__tracepoint_ptrs_registered) {
                ret = dlclose(tracepoint_dlopen_ptr->liblttngust_handle);
                if (ret) {