On Thu, 21 Mar 2024 23:38:30 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: > > Elaborate on 'surprising and undesirable effects' in reachabilityFence() src/java.base/share/classes/java/lang/ref/Reference.java line 576: > 574: * detects that there is no further need for an object. The garbage > collector > 575: * may reclaim an object even if values from that object's fields > are still > 576: * in use, or while a method on the object is still running, so long > as the Suggestion: method _of_ the object src/java.base/share/classes/java/lang/ref/Reference.java line 579: > 577: * object has otherwise become unreachable. > 578: * <p> > 579: * This may have surprising and undesirable effects, in particular > when using Nit: I don't think a new paragraph is appropriate here as "This may ..." refers back to the subject of the preceding lines. src/java.base/share/classes/java/lang/ref/Reference.java line 581: > 579: * This may have surprising and undesirable effects, in particular > when using > 580: * a Cleaner or finalizer for cleanup. If an object becomes > unreachable while > 581: * a method on the object is running, it can lead to a race between > the Again suggest: method _of_ the object src/java.base/share/classes/java/lang/ref/Reference.java line 585: > 583: * Cleaner or finalizer. For instance, the cleanup thread could > cleanup the > 584: * resource, followed by the program thread (still running the > method) > 585: * attempting to access the now-already-freed resource. suggestion: s/cleanup/free/ to match the `now-already-freed` part. src/java.base/share/classes/java/lang/ref/Reference.java line 586: > 584: * resource, followed by the program thread (still running the > method) > 585: * attempting to access the now-already-freed resource. > 586: * {@code reachabilityFence} can prevent this race by ensuring that > the Suggestion: `Use of {@code reachabilityFence ...` This avoids starting a sentence with a code font word that starts with a lower-case letter. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1534946886 PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1534947996 PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1534948233 PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1534948894 PR Review Comment: https://git.openjdk.org/jdk/pull/16644#discussion_r1534949965
