On Wed, 15 Nov 2023 22:31:35 GMT, Stuart Marks <sma...@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."_ > > src/java.base/share/classes/java/lang/ref/Reference.java line 489: > >> 487: * <p>If this reference was already enqueued (by the garbage >> collector, or a >> 488: * previous call to {@code enqueue}), this method is <b><i>not >> successful</i></b>, >> 489: * and returns false. > > If we're going to talk about successful and unsuccessful calls, we should > define what success is first. I guess that would be something like: if this > ref is registered with a queue and not already enqueued, it is enqueued > successfully and the method returns true. Otherwise, not successful, and > returns false. This could be worded as a post condition, after the call the ref is enqueued with the queue; the return is true iff the ref was not previously enqueued. The enqueuing is not conditional (assuming the queue is non-null). ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1401302710
