JVM/TI code review request (XS and M) (7182152)

[Daniel D. Daugherty]

Greetings,

I have a fix for the following JVM/TI bug:

     7182152 Instrumentation hot swap test incorrect monitor count
     http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7182152
     https://jbs.oracle.com/bugs/browse/JDK-7182152

The fix for the bug in the product code is one line:

src/share/vm/oops/klassVtable.cpp:

@@ -992,18 +1020,50 @@
            // RC_TRACE macro has an embedded ResourceMark
            RC_TRACE(0x00200000, ("itable method update: %s(%s)",
              new_method->name()->as_C_string(),
              new_method->signature()->as_C_string()));
          }
-        break;
+        // cannot 'break' here; see for-loop comment above.
        }
        ime++;
      }
    }
  }

and is applicable to JDK7u10/HSX-23.6 and JDK7u14/HSX-24. Coleen
already fixed the bug as part of the Perm Gen Removal (PGR) project
in HSX-25. Yes, we found a 1-line bug fix buried in the monster PGR
changeset. Many thanks to Coleen for her help in this bug hunt!

The rest of the code in the webrevs are:

- additional JVM/TI tracing code backported from Coleen's PGR changeset
- additional JVM/TI tracing code added by me and forward ported to HSX-25
- a new -XX:TraceRedefineClasses=16384 flag value for finding these
   elusive old or obsolete methods
- exposure of some printing code to the PRODUCT build so that the new
   tracing is available in a PRODUCT build

You might be wondering why the new tracing code is exposed in a PRODUCT
build. Well, it appears that more and more PRODUCT bits deployments are
using JVM/TI RedefineClasses() and/or RetransformClasses() at run-time
to instrument their systems. This bug (7182152) was only intermittently
reproducible in the WLS environment in which it occurred so I made the
tracing available in a PRODUCT build to assist in the hunt.

Raj from the WLS team has also verified that the HSX-23.6 version of
fix resolves the issue in his environment. Thanks Raj!

Here are the URLs for the three webrevs:

http://cr.openjdk.java.net/~dcubed/7182152-webrev/0-hsx23.6/
http://cr.openjdk.java.net/~dcubed/7182152-webrev/0-hsx24/
http://cr.openjdk.java.net/~dcubed/7182152-webrev/0-hsx25/

I have run the following test suites from the JPDA stack on the
JDK7u10/HSX-23.6 version of the fix with -XX:TraceRedefineClasses=16384
specified:

     sdk-jdi
     sdk-jdi_closed
     sdk-jli
     vm-heapdump
     vm-hprof
     vm-jdb
     vm-jdi
     vm-jdwp
     vm-jvmti
     vm-sajdi

The tested configs are:

     {Solaris-X86, WinXP}
       X {Client VM, Server VM}
       X {-Xmixed, -Xcomp}
       X {product, fastdebug}

With the 1-liner fix in place, the new tracing code does not find any
instances of this failure mode in any of the above test suites. Without
the the 1-liner fix in place, the new tracing code finds one instance
of this failure mode in the above test suites:

     test/java/lang/instrument/IsModifiableClassAgent.java

There are two new tests that will be pushed to the JDK repos using
a different bug ID (not yet filed):

     test/com/sun/jdi/RedefineAbstractClass.sh
test/java/lang/instrument/RedefineSubclassWithTwoInterfaces.sh

There will be a separate review request for the new tests.

I'm currently running the JPDA stack of tests on the JDK7u14/HSX-24
and JDK8-B75/HSX-25 versions of the fix. That testing will likely
take all weekend to complete.

Thanks, in advance, for any comments and/or suggestions.

Dan