--- old/src/hotspot/share/gc/shared/gc_globals.hpp	2020-08-14 15:37:03.206435687 +0200
+++ new/src/hotspot/share/gc/shared/gc_globals.hpp	2020-08-14 15:37:03.050432932 +0200
@@ -174,10 +174,6 @@
           "Number of parallel threads parallel gc will use")                \
           constraint(ParallelGCThreadsConstraintFunc,AfterErgo)             \
                                                                             \
-  diagnostic(bool, UseSemaphoreGCThreadsSynchronization, true,              \
-            "Use semaphore synchronization for the GC Threads, "            \
-            "instead of synchronization based on mutexes")                  \
-                                                                            \
   product(bool, UseDynamicNumberOfGCThreads, true,                          \
           "Dynamically choose the number of threads up to a maximum of "    \
           "ParallelGCThreads parallel collectors will use for garbage "     \