RFR: 8254264: Remove redundant cross_modify_fence() [v2]

[Patricio Chilano Mateo]

> Hi all,
> 
> Please review the following patch that removes some uneeded uses of cross_modify_fence() in common code, in particular
> from ~ThreadBlockInVM(), ~ThreadBlockInVMWithDeadlockCheck() and java_suspend_self_with_safepoint_check(). These fences
> were added before each JavaThread had to disarm itself (8230594). After a safepoint/handshake each JavaThread will
> always call SafepointMechanism::process_if_requested_slow() when transitioning out of the safe state and will execute a
> cross_modify_fence(). Tested with mach5 tiers1-7.  Thanks, Patricio

Patricio Chilano Mateo has updated the pull request with a new target base due to a merge or a rebase. The incremental
webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional
commits since the last revision:

 - Merge branch 'master' into 8254264-cross_modify_fence
 - Merge branch 'master' into 8254264-cross_modify_fence
 - v1

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/655/files
  - new: https://git.openjdk.java.net/jdk/pull/655/files/38fef27a..9f83608f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=655&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=655&range=00-01

  Stats: 325776 lines in 788 files changed: 312532 ins; 10055 del; 3189 mod
  Patch: https://git.openjdk.java.net/jdk/pull/655.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/655/head:pull/655

PR: https://git.openjdk.java.net/jdk/pull/655