[crac] RFR: Prevent an assertion: Attempting to acquire lock PeriodicTask_lock...

[Jan Kratochvil]

Prevent an assertion: `Attempting to acquire lock PeriodicTask_lock/safepoint out of order with lock Threads_lock/safepoint-1 -- possible deadlock`

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Commit messages:
 - Prevent an assertion: Attempting to acquire lock PeriodicTask_lock/safepoint out of order with lock Threads_lock/safepoint-1 -- possible deadlock

Changes: https://git.openjdk.org/crac/pull/106/files
 Webrev: https://webrevs.openjdk.org/?repo=crac&pr=106&range=00
  Stats: 27 lines in 1 file changed: 25 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/crac/pull/106.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/106/head:pull/106

PR: https://git.openjdk.org/crac/pull/106