On Thu, 1 May 2025 10:20:44 GMT, Maurizio Cimadamore <mcimadam...@openjdk.org> wrote:
>> src/java.base/share/classes/jdk/internal/foreign/BufferStack.java line 163: >> >>> 161: lock.unlock(); >>> 162: } >>> 163: Reference.reachabilityFence(arena); >> >> I'm not sure this is enough to keep the automatic arena alive. If the client >> lets the Frame arena go out of scope w/o calling close, then `arena` will >> become unreachable, but some segments created by the Frame arena might still >> be reachable. To be more correct, I think `Frame` should add a "close >> action" to its confined arena which keeps the outer automatic arena alive. >> This can be done, for instance, by passing a close action to the >> `reinterpret` call: >> >> >> frame = new SlicingAllocator(frameSegment.reinterpret(confinedArena, () -> >> Reference.reachabilityFence(arena))); >> >> >> The close action is installed in the `MemorySession` object of >> `confinedArena` -- which is then attached to all segments returned by >> `Frame` -- thus keeping the automatic arena alive. > > (if you agree with this analysis, perhaps adding an extra stress test, or > tweaking one of the existing stress tests to check this could also be useful) I've thought about it a bit, and I think adding a cleanup action to the reinterpret call is indeed the only fool proof way to add a link back to the parent segment. MemorySegment is what gives a user access to the memory (almost like an access token), so the memory needs to be kept alive through the MS. MS has a reference to its scope, which can then reference the original scope through a cleanup action. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/24829#discussion_r2070510278
