On Fri, 26 Apr 2024 17:59:39 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: > > new section for finalizer memviz src/java.base/share/classes/java/lang/ref/package-info.java line 137: > 135: * <a id="MemoryConsistency"></a> > 136: * <h2>Memory Consistency Properties</h2> > 137: * Certain interactions between references, references queues, and the > garbage Suggestion: * Certain interactions between references, reference queues, and the garbage src/java.base/share/classes/java/lang/ref/package-info.java line 157: > 155: * <li>The dequeuing of a reference to a > 156: * {@linkplain Cleaner#register(Object object, Runnable action) > registered} > 157: * object, by a Cleaner thread, <i>happens-before</i> that Cleaner > thread runs Are we committing to this? I.e. that there will always be a single Cleaner thread? (i.e. one could imagine a situation where you have one polling thread which executes the cleaning action on some other thread?) src/java.base/share/classes/java/lang/ref/package-info.java line 176: > 174: * <li>Actions in a thread prior to calling > 175: * {@link Reference#reachabilityFence Reference.reachabilityFence(x)} > 176: * <i>happen-before</i> the finalizer for x is run by a finalizer > thread.</li> Suggestion: * <i>happen-before</i> the finalizer for {@code x} is run by a finalizer thread.</li> ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1581818740 PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1581818931 PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1581819080
