-an available symbol name or a SystemTap Statically Defined Tracepoints
-(SDT, a DTrace-style marker) probe's provider and probe names. As of
-this version, only SDT probes that are :not: surrounded by a reference
-counter (semaphore).
+an available symbol name or a SystemTap User-level Statically Defined
+Tracing (USDT, a DTrace-style marker) probe's provider and probe names.
+As of this version, only USDT probes that are :not: surrounded by a
+reference counter (semaphore) are supported.