+#ifdef SD_DEBUG_LOCK
+ void _r_dlock(const char *, int); /* in device.c */
+ void _r_dunlock(const char *, int); /* in device.c */
+ void _dlock(const char *, int); /* in device.c */
+ void _dunlock(const char *, int); /* in device.c */
+#else
+ void r_dlock(); /* in device.c */
+ void r_dunlock() { dunlock(); }
+ void dlock() { P(m_mutex); }
+ void dunlock() { V(m_mutex); }
+#endif
+
+ void clear_volhdr(); /* in dev.c */