On Thu, 26 Nov 2020 21:23:16 GMT, Vladimir Ivanov <vliva...@openjdk.org> wrote:
> Concurrent updates may lead to redundant LambdaForms created and unnecessary > class loading when those are compiled. > > Most notably, it severely affects MethodHandle customization: when a > MethodHandle is called from multiple threads, every thread starts > customization which takes enough time for other threads to join, but only one > of those customizations will be picked. > > Coordination between threads requesting the updates and letting a single > thread proceed avoids the aforementioned problem. Moreover, there's no need > to wait until the update in-flight is over: all other threads (except the one > performing the update) can just proceed with the invocation using the > existing MH.form. > > Testing: > - manually monitored the behavior on a stress test from > [JDK-8252049](https://bugs.openjdk.java.net/browse/JDK-8252049) > - tier1-4 src/java.base/share/classes/java/lang/invoke/MethodHandle.java line 1760: > 1758: > 1759: private volatile boolean updateInProgress = false; > 1760: Hi (line 1759): redundant initialization of volatile field to default value is not needed or desired. ------------- PR: https://git.openjdk.java.net/jdk/pull/1472
