RFR: 8278475: G1 dirty card refinement by Java threads may get unnecessarily paused [v2]

[Kim Barrett]

> Please review this change to avoid attempts to refine dirty cards by Java
> threads when there is an active STS yield request, as the attempt will just
> end up being paused.  When going into a safepoint this avoids wasted work and
> transfer of buffers into the paused list.  More importantly, when coming out
> of a pause this avoids deferring buffers to after the next safepoint, due to
> the yield request being cleared after Java threads are restarted.
> 
> Testing:
> mach5 tier1
> 
> Lots of testing as part of investigation of JDK-8273383.

Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:

  fix typo

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7148/files
  - new: https://git.openjdk.java.net/jdk/pull/7148/files/ebadd0aa..4ef92931

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7148&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7148&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7148.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7148/head:pull/7148

PR: https://git.openjdk.java.net/jdk/pull/7148