Summary

Deprecate the unstable HotSpot option -XX:DeferThrSuspendLoopCount=??.

Problem

The option will have no effect once we implement thread suspend with Thread-local handshakes. A user should not try to change this option, hence unstable.

Solution

Deprecate the flag.

Specification

--- a/src/hotspot/share/runtime/arguments.cpp   Wed Nov 15 15:38:36 2017 +0100
+++ b/src/hotspot/share/runtime/arguments.cpp   Wed Nov 15 16:24:54 2017 +0100
@@ -388,2 +388,3 @@
   { "SafepointSpinBeforeYield",     JDK_Version::jdk(10), JDK_Version::jdk(11), JDK_Version::jdk(12) },
+  { "DeferThrSuspendLoopCount",     JDK_Version::jdk(10), JDK_Version::jdk(11), JDK_Version::jdk(12) },
   { "IgnoreUnverifiableClassesDuringDump", JDK_Version::jdk(10),  JDK_Version::undefined(), JDK_Version::undefined() },
diff -r fc697acd5cad src/hotspot/share/runtime/globals.hpp
--- a/src/hotspot/share/runtime/globals.hpp Wed Nov 15 15:38:36 2017 +0100
+++ b/src/hotspot/share/runtime/globals.hpp Wed Nov 15 16:24:54 2017 +0100
@@ -3269,3 +3269,4 @@
   product(intx, DeferThrSuspendLoopCount,     4000,                         \
-          "(Unstable) Number of times to iterate in safepoint loop "        \
+          "(Unstable, Deprecated) "                                         \
+          "Number of times to iterate in safepoint loop "                   \
           "before blocking VM threads ")                                    \