RFR: 8254566: Clarify the spec of ClassLoader::getClassLoadingLock for non-parallel capable loader

[David Holmes]

On Thu, 29 Jun 2023 23:39:55 GMT, Mandy Chung <mchung at openjdk.org> wrote:

> The spec of `ClassLoader::getClassLoadingLock` is unclear that this method is intended for parallel-capable class loader implementations to provide an alternate implementation.   For non-parallel-capable class loaders, this method should return this `ClassLoader` object.   The javadoc uses "the default implementation" which could be interpreted that non-parallel-capable class loaders can also override this implementation, which is not the intent.  See https://openjdk.org/groups/core-libs/ClassLoaderProposal.html.

Looks good. One change requested on terminology.

Thanks

src/java.base/share/classes/java/lang/ClassLoader.java line 656:

> 654:      * @apiNote
> 655:      * This method allows parallel capable class loaders to implement
> 656:      * finer-grained locking scheme such that multiple threads may load classes

s/scheme/schemes/

src/java.base/share/classes/java/lang/ClassLoader.java line 658:

> 656:      * finer-grained locking scheme such that multiple threads may load classes
> 657:      * concurrently without deadlocks.  For non-parallel-capable class loaders,
> 658:      * the {@code ClassLoader} object is held during the class loading operations.

s/is held/is synchronized on/  - as that is the terminology loadClass uses.

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Changes requested by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/14720#pullrequestreview-1506269248
PR Review Comment: https://git.openjdk.org/jdk/pull/14720#discussion_r1247270508
PR Review Comment: https://git.openjdk.org/jdk/pull/14720#discussion_r1247271118