On Mon, 29 Jul 2024 11:26:06 GMT, Jiawei Tang <[email protected]> wrote:
>> test/hotspot/jtreg/serviceability/jvmti/vthread/VThreadTraceWithAgent/TestPinCaseWithTrace.java
>> line 70:
>>
>>> 68: static int native2Java(int b) {
>>> 69: try {
>>> 70: Thread.sleep(500); // try yield, will pin,
>>> javaagent+tracePinnedThreads will crash here (because of the class
>>> `PinnedThreadPrinter`)
>>
>> As noted in the JBS issue, -Djdk.tracePinnedThreads has been very
>> problematic and has been removed in the loom repo as part of the object
>> monitor changes.
>
> I have read the code in loom and this issue can be resolved by using JFR
> event instead. But I hope this could be fixed since using javaagent is very
> common in java application. The root cause is that no new class should be use
> after the vthread is pinned, since a agent can change the class bytecode and
> need to use `JvmtiVTMSTransitionDisabler` when transforming class. However,
> this vthread is in VTMS, it cannot jump out the loop.
>
> Using `-Djdk.tracePinnedThreads=full` will use the class
> `PinnedThreadPrinter` so we end in a deadlock.
I have no objection to fixing JVMTI, I'm just pointing out that
-Djdk.tracePinnedThreads has been very problematic and many other reasons so it
will be proposed to be removed when we bring the changes to main line.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/20373#discussion_r1695136030
