RFR: 8254695: G1: Next mark bitmap clear not cancelled after marking abort

[Thomas Schatzl]

Hi all,

  can I have reviews for this change that fixes aborting the concurrent next bitmap clear if aborted?

The problems are that we can enter the clear loop with the marking already aborted, so
- yielding does not return true any more (marking aborted while joining the STS)  and we never abort in the loop if we
  join all conditions together
- and G1 at least clears the first part(s) of the bitmap as the check is done afterwards

Testing: tier1-5; no more reproducable crashes with other changes (JDK-8253600)

Thanks,
  Thomas

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Commit messages:
 - Initial import next-mark-bitmap-clear-not-cancelled

Changes: https://git.openjdk.java.net/jdk/pull/653/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=653&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254695
  Stats: 12 lines in 1 file changed: 8 ins; 4 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/653.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/653/head:pull/653

PR: https://git.openjdk.java.net/jdk/pull/653