Index: HelenOS.config
===================================================================
--- HelenOS.config	(revision 32d2e6032dc6c247786bec6676b5e3fdd853cca1)
+++ HelenOS.config	(revision b7acf383016ce70e70a5c0df4f6ed935e25629fe)
@@ -405,4 +405,10 @@
 
 
+## User space features options
+
+% Light weight futex locks
+! FUTEX_UPGRADABLE (n/y)
+
+
 ## Hardware support
 
Index: uspace/Makefile.common
===================================================================
--- uspace/Makefile.common	(revision 32d2e6032dc6c247786bec6676b5e3fdd853cca1)
+++ uspace/Makefile.common	(revision b7acf383016ce70e70a5c0df4f6ed935e25629fe)
@@ -227,6 +227,11 @@
 JOBFILE = $(LIBC_PREFIX)/../../../tools/jobfile.py
 
+ifeq ($(FUTEX_UPGRADABLE),y)
+	CFLAGS += -I$(LIBURCU_PREFIX)/
+	LIBS += $(LIBURCU_PREFIX)/liburcu.a
+endif
+
 ifeq ($(POSIX_COMPAT),y)
-	CFLAGS = -I$(LIBPOSIX_PREFIX)/include/posix  -I$(LIBPOSIX_PREFIX)/include/
+	CFLAGS += -I$(LIBPOSIX_PREFIX)/include/posix  -I$(LIBPOSIX_PREFIX)/include/
 	LIBS += $(LIBPOSIX_PREFIX)/libposix.a
 endif