RFR: 8229118: [TESTBUG] serviceability/sa/ClhsdbFindPC fails on AArch64

[Nick Gasson]

Hi,

Bug: https://bugs.openjdk.java.net/browse/JDK-8229118
Webrev: http://cr.openjdk.java.net/~ngasson/8229118/webrev.0/

This test starts a sub-process with -Xcomp and then uses the SA to get a
stack trace of it. It expects to see this line:

  In code in NMethod for jdk/test/lib/apps/LingeredApp.main

But actually on AArch64 the stack trace looks like this:

 - java.lang.Thread.sleep(long) @bci=0, pc=0x0000ffff74603d08, Method*=0x0000ffff031baf98 (Compiled frame; information may be imprecise)
 - jdk.test.lib.apps.LingeredApp.main(java.lang.String[]) @bci=53, line=502, pc=0x0000ffff6c9276e0, Method*=0x0000ffff03611d48 (Interpreted frame)

The main method is interpreted even though we're running with
-Xcomp. That's because it is deoptimized almost immediately, because
main calls some methods on java.nio.file.Paths, but that class hasn't
been loaded when main is compiled. 

X86 can patch in the address of the method on-the-fly, but AArch64 can't
do this because of restrictions on which instructions can be legally
rewritten.

This patch lifts the code that uses the java.nio classes out of
LingeredApp::main into a separate static method. LingeredApp.main now
only uses classes that are loaded very early in boot, before main is
compiled. The stack trace now looks like:

"main" #1 prio=5 tid=0x0000ffffb4022800 nid=0xd610 waiting on condition [0x0000ffffbb755000]
   java.lang.Thread.State: TIMED_WAITING (sleeping)
   JavaThread state: _thread_blocked
 - java.lang.Thread.sleep(long) @bci=0, pc=0x0000fffface414c8, Method*=0x0000ffff3dac8a28 (Compiled frame; information may be imprecise)
 - jdk.test.lib.apps.LingeredApp.pollLockFile(java.lang.String) @bci=30, line=499, pc=0x0000ffffa50818e0, Method*=0x0000ffff3c122cf0 (Interpreted frame)
 - jdk.test.lib.apps.LingeredApp.main(java.lang.String[]) @bci=25, line=529, pc=0x0000ffffa59afd58, Method*=0x0000ffff3c122de0 (Compiled frame)

I.e. pollLockFile was deoptimized to an interpreted frame but
LingeredApp.main is still a compiled frame which is what ClhsdbFindPC is
looking for.

This solution does seem a bit hacky, so if it's not acceptable an
alternative is to just skip the -Xcomp part of the test on AArch64.

Ran a full jtreg test on AArch64/x86 to check for regressions.

Thanks,
Nick