On Wed, 15 Jul 2026 19:38:05 GMT, Jorn Vernee <[email protected]> wrote:
>> The methods `load()`, `unload()`, `isLoaded()`, and `force()` in >> `MemorySegment` currently delegate to `ScopedMemoryAccess` through a set of >> `@Scoped` methods, after which the implementation calls into >> `java.nio.MappedMemoryUtils`. This means that, when a shared scope is closed >> during a call to one of these methods, an exception can be installed at any >> point during the execution of the util method. >> >> The problem is that some parts of these methods are not able to handle such >> exceptions being installed. >> >> We've had some previous discussion about these methods not really needing to >> be `@Scoped` in the first place, but instead being able to rely on paired >> acquire/release of the session being accessed. This code is not as >> performance critical compared to a scoped memory access, since we're doing a >> native call any way. >> >> To avoid issues with exceptions being installed in surprising places, this >> patch switches the named methods to use acquire/release instead of being >> `@Scoped`. This changes the behavior of these methods slightly: they now >> keep the scope alive during the execution of the method. I've updated the >> doc, borrowing from existing text in the `Linked::downcallHandle` docs, to >> explain that a scope closure may now fail during the execution of one of >> these methods. >> >> Does this seem like the right tradeoff? >> >> --------- >> - [x] I confirm that I make this contribution in accordance with the >> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). > > src/java.base/share/classes/jdk/internal/misc/X-ScopedMemoryAccess.java.template > line 241: > >> 239: >> 240: @ForceInline >> 241: public boolean isLoaded(MemorySessionImpl session, >> MappedMemoryUtilsProxy mappedUtils, long address, boolean isSync, long size) >> { > > This method is called by both the memory segment and byte buffer > implementations, so I chose to keep the implementation centralized here, > instead of having each client replicate the acquire/release code. Also, MappedMemoryUtils was accessed through a proxy to ensure that the class is fully initialized before entering the `@Scoped` section. I've kept this pattern, as it seemed generally desirable to keep the time spent keeping the scope acquire to a minimum, rather than potentially having to initialize MappedMemoryUtils while the scope is acquired. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/31918#discussion_r3590247777
