--- old/src/hotspot/cpu/sparc/globals_sparc.hpp	2019-10-17 17:31:24.000000000 -0400
+++ new/src/hotspot/cpu/sparc/globals_sparc.hpp	2019-10-17 17:31:23.000000000 -0400
@@ -84,6 +84,9 @@
 define_pd_global(intx, InitArrayShortSize, 8*BytesPerLong);
 
 define_pd_global(bool, ThreadLocalHandshakes, true);
+// ObjectMonitor ref_count not implemented in C2 fast_lock() or
+// fast_unlock() so use a handshake for safety.
+define_pd_global(bool, HandshakeAfterDeflateIdleMonitors, true);
 
 #define ARCH_FLAGS(develop, \
                    product, \