On Mon, 30 Nov 2020 12:57:36 GMT, Coleen Phillimore <[email protected]> wrote:
>> 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();
> }
That isn't quite what I asked. The claim is that `remove_dead_entries_locked`
needs to recheck `is_enabled` if `post_object_free` is true in case the enabled
state changed from true to false. But I can't see how such a situation can
arise. In `flush_object_free_events` we only call `remove_dead_entries(false)`
and that is when events were seen to be disabled.
-------------
PR: https://git.openjdk.java.net/jdk/pull/1439
