On Fri, 27 Nov 2020 02:26:44 GMT, David Holmes <dhol...@openjdk.org> wrote:
>> The ServiceThread cleaning used a stale ObjectFree state when calling
>> remove_dead_entries, because another thread had concurrently set is_enabled
>> to false. Add a lock around setting/resetting the lock event state and
>> retest the state under a lock. Ran the test 100s of time without failure,
>> where otherwise it fails very quickly.
>> Tested with tier2,3 and running tiers 4,5,6 in progress.
>> Thanks to Kim for his previous feedback.
>
> src/hotspot/share/prims/jvmtiTagMap.cpp line 1162:
>
>> 1160: if (_needs_cleaning) {
>> 1161: // Recheck whether to post object free events under the lock.
>> 1162: post_object_free = post_object_free &&
>> env()->is_enabled(JVMTI_EVENT_OBJECT_FREE);
>
> Where is `is_enabled` called without the lock being held in a caller of
> `remove_dead_entries()`?
void JvmtiTagMap::flush_object_free_events() {
assert_not_at_safepoint();
if (env()->is_enabled(JVMTI_EVENT_OBJECT_FREE)) {
Called by JVMTI to disable events and called by the service thread. And here
for get_objects_with_tags:
if (collector.some_dead_found() &&
env()->is_enabled(JVMTI_EVENT_OBJECT_FREE)) {
post_dead_objects_on_vm_thread();
}
-------------
PR: https://git.openjdk.java.net/jdk/pull/1439
