Fix: ensure all probe providers have their symbols

Original commit log from stable-2.2:
Following the removal of metadata generation from UST, the probes cannot
find the tracepoint_dlopen() symbol. Ensure those probes can be built by
declaring this symbol within each probe.

stable-2.1 backport:
Similar issue was experienced with the "demo" test program when built
outside of the UST tree.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h
index ef41837c6b6b0d9a716ba70ee07c40d10a7cab41..3433560a10e9d2ce220cb925a0252c01211bc391 100644 (file)
--- a/include/lttng/tracepoint.h
+++ b/include/lttng/tracepoint.h
@@ -215,6 +215,16 @@ extern struct tracepoint_dlopen tracepoint_dlopen;
 
 #ifdef TRACEPOINT_DEFINE
 
+/*
+ * These weak symbols, the constructor, and destructor take care of
+ * registering only _one_ instance of the tracepoints per shared-ojbect
+ * (or for the whole main program).
+ */
+extern struct tracepoint * const __start___tracepoints_ptrs[]
+       __attribute__((weak, visibility("hidden")));
+extern struct tracepoint * const __stop___tracepoints_ptrs[]
+       __attribute__((weak, visibility("hidden")));
+
 /*
  * When TRACEPOINT_PROBE_DYNAMIC_LINKAGE is defined, we do not emit a
  * unresolved symbol that requires the provider to be linked in. When
@@ -255,15 +265,41 @@ extern struct tracepoint_dlopen tracepoint_dlopen;
                __attribute__((used, section("__tracepoints_ptrs"))) =          \
                        &__tracepoint_##_provider##___##_name;
 
+static inline void __tracepoints__init_define(void)
+{
+       tracepoint_dlopen.tracepoint_register_lib(__start___tracepoints_ptrs,
+                               __stop___tracepoints_ptrs -
+                               __start___tracepoints_ptrs);
+}
+
+static inline void __tracepoints__destroy_define(void)
+{
+       if (tracepoint_dlopen.tracepoint_unregister_lib)
+               tracepoint_dlopen.tracepoint_unregister_lib(__start___tracepoints_ptrs);
+}
+
+
+#else /* TRACEPOINT_DEFINE */
+
+#define _DEFINE_TRACEPOINT(_provider, _name, _args)
+
+static inline void __tracepoints__init_define(void)
+{
+}
+
+static inline void __tracepoints__destroy_define(void)
+{
+}
+
+#endif /* #else TRACEPOINT_DEFINE */
+
+#if defined(TRACEPOINT_DEFINE) || defined(TRACEPOINT_CREATE_PROBES)
+
 /*
  * These weak symbols, the constructor, and destructor take care of
  * registering only _one_ instance of the tracepoints per shared-ojbect
  * (or for the whole main program).
  */
-extern struct tracepoint * const __start___tracepoints_ptrs[]
-       __attribute__((weak, visibility("hidden")));
-extern struct tracepoint * const __stop___tracepoints_ptrs[]
-       __attribute__((weak, visibility("hidden")));
 int __tracepoint_registered
        __attribute__((weak, visibility("hidden")));
 struct tracepoint_dlopen tracepoint_dlopen
@@ -303,11 +339,7 @@ __tracepoints__init(void)
                                dlsym(tracepoint_dlopen.liblttngust_handle,
                                        "tp_rcu_dereference_sym_bp"));
 #endif
-       if (tracepoint_dlopen.tracepoint_register_lib) {
-               tracepoint_dlopen.tracepoint_register_lib(__start___tracepoints_ptrs,
-                                       __stop___tracepoints_ptrs -
-                                       __start___tracepoints_ptrs);
-       }
+       __tracepoints__init_define();
 }
 
 static void lttng_ust_notrace __attribute__((destructor))
@@ -319,8 +351,7 @@ __tracepoints__destroy(void)
 
        if (--__tracepoint_registered)
                return;
-       if (tracepoint_dlopen.tracepoint_unregister_lib)
-               tracepoint_dlopen.tracepoint_unregister_lib(__start___tracepoints_ptrs);
+       __tracepoints__destroy_define();
        if (tracepoint_dlopen.liblttngust_handle) {
                ret = dlclose(tracepoint_dlopen.liblttngust_handle);
                assert(!ret);
@@ -328,11 +359,7 @@ __tracepoints__destroy(void)
        }
 }
 
-#else /* TRACEPOINT_DEFINE */
-
-#define _DEFINE_TRACEPOINT(_provider, _name, _args)
-
-#endif /* #else TRACEPOINT_DEFINE */
+#endif
 
 #ifdef __cplusplus
 }