RFR: 8255381: com/sun/jdi/EATests.java should not suspend graal threads [v2]

[Richard Reingruber]

> This fixes a bug in the test test/jdk/com/sun/jdi/EATests.java that caused
> timeout failures when graal is enabled.
> 
> The fix is to avoid suspending all threads when a breakpoint is reached and then resume
> just the main thread again. This pattern was used in the test case
> EAMaterializeLocalAtObjectPollReturnReturn. It caused timeouts because graal
> threads remained suspended and, running with -Xbatch, the main thread waited
> (with timeout) for completion of compile tasks.
> The fix was applied to all breakpoints in the test. All explicit suspend calls now apply only
> to the main test thread and all explicit resume calls apply to all java threads.
> 
> Testing: duration of the test case EAMaterializeLocalAtObjectPollReturnReturn is
> reduced from 30s to 10s.

Richard Reingruber has updated the pull request incrementally with one additional commit since the last revision:

  Changes based on Chris Plummer's feedback.

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1625/files
  - new: https://git.openjdk.java.net/jdk/pull/1625/files/39f5a1e9..8e4b301f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1625&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1625&range=00-01

  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1625.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1625/head:pull/1625

PR: https://git.openjdk.java.net/jdk/pull/1625