RFR: 8261391: ZGC crash - SEGV in RevokeOneBias::do_thread [v3]

[Robbin Ehn]

> Handshakes may contain oop Handles from the requesting thread.
> A handshake may be executed by another thread than the requester.
> We must make sure any such Handle is safe to use by other threads before executing the handshake.
> This change-set adds SWS::start_process() for the requesting thread also (we already do this for the target JavaThread).
> 
> Passes t1-5

Robbin Ehn has updated the pull request incrementally with one additional commit since the last revision:

  Tiny spelling error

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2571/files
  - new: https://git.openjdk.java.net/jdk/pull/2571/files/7245e442..69330c1b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2571&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2571&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2571.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2571/head:pull/2571

PR: https://git.openjdk.java.net/jdk/pull/2571