RFR: 8338383: Implement JEP 491: Synchronize Virtual Threads without Pinning [v22]

[Alan Bateman]

On Thu, 31 Oct 2024 20:13:31 GMT, Dean Long <dlong at openjdk.org> wrote:

>> Patricio Chilano Mateo has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix typos in comments
>
> src/java.base/linux/classes/sun/nio/ch/EPollSelectorImpl.java line 108:
> 
>> 106:         processDeregisterQueue();
>> 107: 
>> 108:         if (Thread.currentThread().isVirtual()) {
> 
> It looks like we have two implementations, depending on if the current thread is virtual or not.  The two implementations differ in the way they signal interrupted.  Can we unify the two somehow?

When executed on a platform thread is will block in epoll_wait or kqueue so it has to handle EINTR. It doesn't block in sys call when executed in a virtual thread. So very different implementations.

> test/hotspot/jtreg/compiler/codecache/stress/OverloadCompileQueueTest.java line 42:
> 
>> 40:  *                   -XX:CompileCommand=exclude,java.lang.Thread::beforeSleep
>> 41:  *                   -XX:CompileCommand=exclude,java.lang.Thread::afterSleep
>> 42:  *                   -XX:CompileCommand=exclude,java.util.concurrent.TimeUnit::toNanos
> 
> I'm guessing these changes have something to do with JDK-8279653?

It should have been added when Thread.sleep was changed but we got lucky.

> test/hotspot/jtreg/serviceability/jvmti/events/MonitorContendedEnter/mcontenter01/libmcontenter01.cpp line 73:
> 
>> 71: /* ========================================================================== */
>> 72: 
>> 73: static int prepare(JNIEnv* jni) {
> 
> Is this a bug fix?

Testing ran into a couple of bugs in JVMTI tests. One of was tests that was stashing the JNIEnv into a static.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1825115214
PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1825112326
PR Review Comment: https://git.openjdk.org/jdk/pull/21565#discussion_r1825110254