Bug ID: JDK-8258800 Deprecate -XX:+AlwaysLockClassLoader

Type: Enhancement
Component: hotspot
Sub-Component: runtime
Affected Version: 17

Priority: P3
Status: Resolved
Resolution: Fixed

Submitted: 2020-12-21
Updated: 2021-01-12
Resolved: 2021-01-04

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JDK 17
17 b04Fixed

This option was added when parallel capable class loading was added in JDK 7 to help users debug their parallel capable class loaders that might have bugs.  Allowing general access to this functionality can cause deadlocks, so this shouldn't be an option for users.  Nor is is useful for debugging parallel capable class loaders, since it may only hide their bugs.
This option is untested (and should be because it'll cause deadlocks) and should be deprecated in 17, obsoleted in 18 and removed in 19.

From: http://openjdk.java.net/groups/core-libs/ClassLoaderProposal.html

VM Flags for early access testing
AlwaysLockClassLoader - default false. Provided for ParallelClassLoader that has a bug in handling multiple threads in parallel. Expected to ship in product.

CSR :	JDK-8258801 - Deprecate -XX:+AlwaysLockClassLoader
Relates :	JDK-8259066 - Obsolete -XX:+AlwaysLockClassLoader
Relates :	JDK-7071060 - Deadlock occurs in java.lang.instrumentation
Relates :	JDK-4670071 - java.lang.ClassLoader.loadClassInternal(String) is too restrictive