RFR(T): 8252126: 'GVars.stw_random = os::random()' lost by JDK-8246476

[Daniel D. Daugherty]

Greetings,

Thanks to Erik O. for spotting this lost line of code!

I have a trivial fix for a piece of code that was accidentally lost with
the push of another ObjectMonitor fix (8246476). Here's the bug ID for
restoring the line of code:

     JDK-8252126 'GVars.stw_random = os::random()' lost by JDK-8246476
     https://bugs.openjdk.java.net/browse/JDK-8252126

And here's the context diff for the trivial change itself:

$ hg diff -r qparent
diff -r 8f73aeccb27c src/hotspot/share/runtime/synchronizer.cpp
--- a/src/hotspot/share/runtime/synchronizer.cpp    Thu Aug 20 11:12:00 
2020 -0700
+++ b/src/hotspot/share/runtime/synchronizer.cpp    Thu Aug 20 16:40:10 
2020 -0400
@@ -2322,6 +2322,8 @@
Atomic::load(&om_list_globals._free_count),
Atomic::load(&om_list_globals._wait_count));

+  GVars.stw_random = os::random();
+
    // The ServiceThread's async deflation request has been processed.
    _last_async_deflation_time_ns = os::javaTimeNanos();
    set_is_async_deflation_requested(false);


I've added a couple of analysis comments to the bug report for anyone
that wants to read the gory details.

This fix has been tested as part of a larger ObjectMonitor fix that
will take some time to get through the code review, stress test and
performance testing process.

Thanks, in advance, for any comments, questions or suggestions.

Dan