From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Date: Wed, 16 Sep 2009 13:30:22 +0000 (-0400)
Subject: Expose nop QSBR read lock to non-GPL/LGPL programs
X-Git-Tag: v0.1~85
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=727f819de5737f4be5b9f7e50aacf84c7a3f7999;p=userspace-rcu.git

Expose nop QSBR read lock to non-GPL/LGPL programs

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---

diff --git a/urcu-qsbr.c b/urcu-qsbr.c
index d1f5d91..ccecab4 100644
--- a/urcu-qsbr.c
+++ b/urcu-qsbr.c
@@ -32,6 +32,7 @@
 #include <errno.h>
 #include <poll.h>
 
+#define BUILD_QSBR_LIB
 #include "urcu-qsbr-static.h"
 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
 #include "urcu-qsbr.h"
diff --git a/urcu-qsbr.h b/urcu-qsbr.h
index 1dc4ddd..9a2c82f 100644
--- a/urcu-qsbr.h
+++ b/urcu-qsbr.h
@@ -66,9 +66,32 @@
  * library wrappers to be used by non-LGPL compatible source code.
  */
 
+/*
+ * QSBR read lock/unlock are guaranteed to be no-ops. Therefore, we expose them
+ * in the LGPL header for any code to use. However, the debug version is not
+ * nops and may contain sanity checks. To activate it, applications must be
+ * recompiled with -DURCU_DEBUG (even non-LGPL/GPL applications). This is the
+ * best trade-off between license/performance/code triviality and
+ * library debugging & tracing features we could come up with.
+ */
+
+#if (!defined(BUILD_QSBR_LIB) && defined(URCU_DEBUG))
+
+static inline void rcu_read_lock(void)
+{
+}
+
+static inline void rcu_read_lock(void)
+{
+}
+
+#else /* !URCU_DEBUG */
+
 extern void rcu_read_lock(void);
 extern void rcu_read_unlock(void);
 
+#endif /* !URCU_DEBUG */
+
 extern void *rcu_dereference(void *p);
 
 extern void rcu_quiescent_state(void);