Can't build. Error pthread_rwlock_t

Hi all
I try to build a project but it show me:

In file included from accel-ppp-code/accel-pppd/session_backup.c:11:0:
accel-ppp-code/accel-pppd/include/ap_session.h:129:8: error: unknown type name 'pthread_rwlock_t'
extern pthread_rwlock_t ses_lock;
^~~~~~~~~~~~~~~~
make[2]: *** [accel-pppd/CMakeFiles/accel-pppd.dir/build.make:111: accel-pppd/CMakeFiles/accel-pppd.dir/session_backup.c.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:115: accel-pppd/CMakeFiles/accel-pppd.dir/all] Error 2
make: *** [Makefile:152: all] Error 2

What i need to do?