On Thu, 14 Mar 2024 23:23:07 GMT, Brent Christian <bchri...@openjdk.org> wrote:
>> Classes in the `java.lang.ref` package would benefit from an update to bring >> the spec in line with how the VM already behaves. The changes would focus on >> _happens-before_ edges at some key points during reference processing. >> >> A couple key things we want to be able to say are: >> - `Reference.reachabilityFence(x)` _happens-before_ reference processing >> occurs for 'x'. >> - `Cleaner.register()` _happens-before_ the Cleaner thread runs the >> registered cleaning action. >> >> This will bring Cleaner in line (or close) with the memory visibility >> guarantees made for finalizers in [JLS >> 17.4.5](https://docs.oracle.com/javase/specs/jls/se18/html/jls-17.html#jls-17.4.5): >> _"There is a happens-before edge from the end of a constructor of an object >> to the start of a finalizer (ยง12.6) for that object."_ > > Brent Christian has updated the pull request incrementally with one > additional commit since the last revision: > > further tweaks to reachability src/java.base/share/classes/java/lang/ref/Reference.java line 402: > 400: * method is called, the garbage collector may already be in the > process of > 401: * (or already completed) clearing and/or enqueueing this reference. > 402: * Either this is an extra blank line, or you need a `<p>` here. src/java.base/share/classes/java/lang/ref/Reference.java line 496: > 494: * Actions in a thread prior to calling > 495: * {@code enqueue} <b><i>successfully</i></b> > 496: * <a > href="{@docRoot}/java.base/java/util/concurrent/package-summary.html#MemoryVisibility"><i>happen-before</i></a> Editorial. The text here says > Actions in a thread prior to calling `enqueue` successfully _happen-before_ > the reference is removed... This could be confusing, because "successfully" might be read to modify "happen-before". This raises questions such as "Is it possible for something to happen-before unsuccessfully?" Of course you want "successfully" to modify "enqueue" because you're relying on the definition of "successful" given previously. Suggest rewording: > Actions in a thread prior to successful calls to `enqueue` _happen-before_ > the reference is removed... src/java.base/share/classes/java/lang/ref/package-info.java line 127: > 125: * thread prior to a {@link Reference#reachabilityFence > Reference.reachabilityFence(x)} > 126: * <i>happen-before</i> cleanup code for {@code x} runs on the cleaner > thread. > 127: * Extra blank line or need `<p>`. src/java.base/share/classes/java/lang/ref/package-info.java line 146: > 144: * > 145: * <li> An object is <em>strongly reachable</em> if it can be accessed > without > 146: * traversing the referent of a Reference object. Here, we want the definition of "strongly reachable" to build on the JLS definition of "reachable" quoted above. Suggest something like > An object is **strongly reachable** if it is reachable and if it can be > accessed without traversing the referent of a Reference object. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1527074234 PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1527080061 PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1527074924 PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1527076814
