RFR: 8307365: JvmtiStressModule hit SIGSEGV in JvmtiEventControllerPrivate::recompute_thread_enabled [v4]

[Leonid Mesnik]

On Tue, 16 May 2023 23:43:51 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

>> The following patch fixes a bug introduced while refactoring the VirtualThreadStart/End events. Specifically, the code to delete the JvmtiThreadState of a terminating vthread was moved before we start the VTMS transition. That allowed said code to run concurrently with recompute_enabled() leading to different crashing modes. I wrote the detailed sequence of events leading to the crash in the bug comments. 
>> 
>> To fix it I moved the cleanup code back after the call to VTMS_unmount_begin(). Now, since the rebinding of the JvmtiThreadState to that of the carrier has to be done after this cleanup code is executed, otherwise we would delete the wrong JvmtiThreadState state, I had to add a boolean argument to VTMS_unmount_begin() to differentiate the last unmount call from the other ones. This is unfortunate since ideally VTMS_unmount_begin() would be oblivious to these two cases as with VTMS_mount_end() where we don't need to check if this is the first mount.
>> I looked for other ways to solve it instead of the extra boolean argument but wasn't convinced. One way would be to have another JvmtiExport::cleanup_thread() that would handle this case. Another way which is very simple is to move the rebind_to_jvmti_thread_state_of() call to VTMS_unmount_end() instead. But that means during the transition the _jvmti_thread_state field of the carrier would be either null or that of the vthread, unlike today which is always that of the carrier during the transitions. I didn't want to change that behavior in this fix but I can also explore that route.
>> 
>> I tested the patch with the reproducer I attached to the bug, plus I also run tiers1-3 in mach5.
>> 
>> Thanks,
>> Patricio
>
> Patricio Chilano Mateo has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Serguei test comments

Marked as reviewed by lmesnik (Reviewer).

test/hotspot/jtreg/serviceability/jvmti/vthread/ThreadStateTest/ThreadStateTest.java line 44:

> 42:     static final int VTHREAD_COUNT = 64;
> 43: 
> 44:     private static native void SetSingleSteppingMode(boolean enable);

Could you please rename them to 's'etSingleSteppingMode and 's'etMonitorContendedMode.

test/hotspot/jtreg/serviceability/jvmti/vthread/ThreadStateTest/ThreadStateTest.java line 58:

> 56: 
> 57:         while (tryCount-- > 0) {
> 58:             ExecutorService scheduler = Executors.newFixedThreadPool(8);

Is it possible to configure pool using any of these parameters?
-Djdk.defaultScheduler.parallelism= 
 -Djdk.defaultScheduler.maxPoolSize=

test/hotspot/jtreg/serviceability/jvmti/vthread/ThreadStateTest/ThreadStateTest.java line 93:

> 91: 
> 92:     public static void main(String[] args) throws Exception {
> 93:         try {

You could just remove try/catch.

-------------

PR Review: https://git.openjdk.org/jdk/pull/13949#pullrequestreview-1429692613
PR Review Comment: https://git.openjdk.org/jdk/pull/13949#discussion_r1195858682
PR Review Comment: https://git.openjdk.org/jdk/pull/13949#discussion_r1195860865
PR Review Comment: https://git.openjdk.org/jdk/pull/13949#discussion_r1195859018