RFR: 8282477: [x86, aarch64] vmassert(_last_Java_pc == NULL, "already walkable"); fails with async profiler [v2]

[Johannes Bechberger]

> Fix the assertion by replacing it by assertion that does not fail.

Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:

  Do not alter JFA in sender_for_entry

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8209/files
  - new: https://git.openjdk.java.net/jdk/pull/8209/files/778e8418..f152367b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8209&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8209&range=00-01

  Stats: 40 lines in 5 files changed: 21 ins; 4 del; 15 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8209.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8209/head:pull/8209

PR: https://git.openjdk.java.net/jdk/pull/8209