Fix: initialize RCU callbacks with mixed LGPL/non-LGPL objects

Linking both _LGPL_SOURCE and non-_LGPL_SOURCE objects into the same
module may result in having the RCU callbacks left to NULL, which
prevents tracing for tracepoints and/or probes which sit in the non-LGPL
compile unit.

This happens if the contructor of the LGPL compile unit is executed
first, thus incrementing the __tracepoint_registered counter, which will
prevent later execution of that same constructor in the non-LGPL compile
unit to initialize the RCU callbacks in __tracepoint__init_urcu_sym().

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h
index 17cbd41f93b1d11d972b867e7924eda2cca72c87..c80da9216dfdef1eaa1c9b16678188c77a9a2c08 100644 (file)
--- a/include/lttng/tracepoint.h
+++ b/include/lttng/tracepoint.h
@@ -294,8 +294,12 @@ __tracepoints__init(void);
 static void
 __tracepoints__init(void)
 {
-       if (__tracepoint_registered++)
+       if (__tracepoint_registered++) {
+               if (!tracepoint_dlopen_ptr->liblttngust_handle)
+                       return;
+               __tracepoint__init_urcu_sym();
                return;
+       }
 
        if (!tracepoint_dlopen_ptr)
                tracepoint_dlopen_ptr = &tracepoint_dlopen;