Fix dynamic linking with GNU gold linker

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

diff --git a/include/lttng/tracepoint-rcu.h b/include/lttng/tracepoint-rcu.h
new file mode 100644 (file)
index 0000000..852cfe4
--- /dev/null
+++ b/include/lttng/tracepoint-rcu.h
@@ -0,0 +1,49 @@
+#ifndef _LTTNG_TRACEPOINT_RCU_H
+#define _LTTNG_TRACEPOINT_RCU_H
+
+/*
+ * Copyright (c) 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
+ * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
+ *
+ * Permission is hereby granted to use or copy this program
+ * for any purpose,  provided the above notices are retained on all copies.
+ * Permission to modify the code and to distribute modified code is granted,
+ * provided the above notices are retained, and a notice that the code was
+ * modified is included with the above copyright notice.
+ *
+ * This file allows weak linking on tracepoint RCU symbols for non-LGPL
+ * code.
+ */
+
+#include <urcu/compiler.h>
+
+#ifdef _LGPL_SOURCE
+
+#include <urcu-bp.h>
+
+#define TP_RCU_LINK_TEST()     1
+#define tp_rcu_read_lock_bp    rcu_read_lock_bp
+#define tp_rcu_read_unlock_bp  rcu_read_unlock_bp
+#define tp_rcu_dereference_bp  rcu_dereference_bp
+
+#else  /* _LGPL_SOURCE */
+
+#define TP_RCU_LINK_TEST()     tp_rcu_read_lock_bp
+
+/* Symbols looked up with dlsym */
+static void (*tp_rcu_read_lock_bp)(void) __attribute__((unused));
+static void (*tp_rcu_read_unlock_bp)(void) __attribute__((unused));
+static void *(*tp_rcu_dereference_sym_bp)(void *p) __attribute__((unused));
+
+#define tp_rcu_dereference_bp(p)                                            \
+       ({                                                                   \
+               typeof(p) _________p1 = URCU_FORCE_CAST(typeof(p),           \
+                       tp_rcu_dereference_sym_bp(URCU_FORCE_CAST(void *, p))); \
+               (_________p1);                                               \
+       })
+
+#endif /* _LGPL_SOURCE */
+
+#endif /* _LTTNG_TRACEPOINT_RCU_H */