On Fri, 11 Jul 2025 14:27:21 GMT, Chen Liang <li...@openjdk.org> wrote:
>> On 32 bit platforms, when an access to long/double is aligned, it is >> supported but not atomic. The original wording in >> `MethodHandles::byteBufferViewVarHandle` sounds as if it is not supported at >> all. We can fix that by borrowing the improved specification from >> `MemoryLayout::varHandle`. >> >> Note: This doc is copied from >> https://github.com/openjdk/jdk/blob/ee0d309bbd33302d8c6f35155e975db77aaea785/src/java.base/share/classes/java/lang/foreign/MemoryLayout.java#L279-L282 >> with slight adjustments. See the rendering at >> https://docs.oracle.com/en/java/javase/24/docs/api/java.base/java/lang/foreign/MemoryLayout.html#access-mode-restrictions > > Chen Liang has updated the pull request incrementally with one additional > commit since the last revision: > > Correct term is atomic, not word tearing src/java.base/share/classes/java/lang/foreign/MemoryLayout.java line 281: > 279: * <li>read write access modes for all {@code T}. On 32-bit platforms, > access modes > 280: * {@code get} and {@code set} for {@code long}, {@code double} and > {@code MemorySegment} > 281: * are supported but not atomic, as described in Section {@jls 17.7} Pedantically it is "... but are not guaranteed to be atomic, ...", since IIUC some 32-bit CPU architectures support 64-bit loads and stores (e.g., the ARM A32 LDREXD instruction) so the JVM can do something stronger than what is prescribed by the JMM. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/26258#discussion_r2201432837
