RFR: 8277631: ZGC: CriticalMetaspaceAllocation asserts

[Per Liden]

On Tue, 23 Nov 2021 14:14:31 GMT, Erik Österlund <eosterlund at openjdk.org> wrote:

> The MetaspaceCritical_lock is a non-safepoint checking lock. That implies that the allow VM block flag is true. That implies that taking that lock takes a NoSafepointVerifier. That causes an assert to fire when MetaspaceCriticalAllocation::wait_for_purge transitions to blocked with ThreadBlockInVM while holding the lock. The fix is to move the locker inside of the ThreadBlockInVM.

Marked as reviewed by pliden (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/6520