Cygwin: Fix multiple loaded instances of liblttng-ust-tracepoint due to dlopen

Multiple instances of the liblttng-ust-tracepoint were present in memory and
caused duplication and incoherence of various data structures (such as the
tracepoints hashtable). This is due to the dlopen(3) of liblttng-ust-tracepoint
in applications that were already linked against liblttng-ust-tracepoint.

This commit introduce a new restriction on application tracing:
the applications must be linked against liblttng-ust-tracepoint.

diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h
index 01561d81f4bebe62c7f4df35accb62504baaf681..7d714db84a67b73f56c183a48770be2f776a1586 100644 (file)
--- a/include/lttng/tracepoint.h
+++ b/include/lttng/tracepoint.h
@@ -249,30 +249,26 @@ static void __attribute__((constructor)) __tracepoints__init(void)
        if (__tracepoint_registered++)
                return;
 
-       tracepoint_dlopen.liblttngust_handle =
-               dlopen("liblttng-ust-tracepoint.so.0", RTLD_NOW | RTLD_GLOBAL);
-       if (!tracepoint_dlopen.liblttngust_handle)
-               return;
        tracepoint_dlopen.tracepoint_register_lib =
                URCU_FORCE_CAST(int (*)(struct tracepoint * const *, int),
-                               dlsym(tracepoint_dlopen.liblttngust_handle,
+                               dlsym(RTLD_DEFAULT,
                                        "tracepoint_register_lib"));
        tracepoint_dlopen.tracepoint_unregister_lib =
                URCU_FORCE_CAST(int (*)(struct tracepoint * const *),
-                               dlsym(tracepoint_dlopen.liblttngust_handle,
+                               dlsym(RTLD_DEFAULT,
                                        "tracepoint_unregister_lib"));
 #ifndef _LGPL_SOURCE
        tracepoint_dlopen.rcu_read_lock_sym_bp =
                URCU_FORCE_CAST(void (*)(void),
-                               dlsym(tracepoint_dlopen.liblttngust_handle,
+                               dlsym(RTLD_DEFAULT,
                                        "tp_rcu_read_lock_bp"));
        tracepoint_dlopen.rcu_read_unlock_sym_bp =
                URCU_FORCE_CAST(void (*)(void),
-                               dlsym(tracepoint_dlopen.liblttngust_handle,
+                               dlsym(RTLD_DEFAULT,
                                        "tp_rcu_read_unlock_bp"));
        tracepoint_dlopen.rcu_dereference_sym_bp =
                URCU_FORCE_CAST(void *(*)(void *p),
-                               dlsym(tracepoint_dlopen.liblttngust_handle,
+                               dlsym(RTLD_DEFAULT,
                                        "tp_rcu_dereference_sym_bp"));
 #endif
        tracepoint_dlopen.tracepoint_register_lib(__start___tracepoints_ptrs,