On Tue, 1 Dec 2020 12:44:24 GMT, Coleen Phillimore <cole...@openjdk.org> wrote:
> The JvmtiTagMap can be deleted while it is posting. The JvmtiEnv is still on > the list but the env is "disposed" of and the tag_map is deleted to save > memory until the JvmtiEnv can be reclaimed at a safepoint and taken off the > list. > > There's a check JvmtiEnvBase::check_for_periodic_clean_up() that determines > whether the JvmtiEnv can be taken off the list and that check looks for > whether threads are in the middle of JvmtiEnvIterator which sets > Thread::jvmti_env_iteration_count. So this part is safe for the JvmtiTagMap > changes. > > The fix is to clear the JvmtiTagMapTable of the entries inside the table lock > to save memory but leave JvmtiTagMap intact so that we can load a valid > pointer when iterating through JvmtiEnvIterator. We could also not do this > at all and let the JvmtiTagMap destructor delete the table when the JvmtiEnv > is also deleted, but we don't know what customer situation led to this code > in the first place. This pull request has now been integrated. Changeset: 2508bc7c Author: Coleen Phillimore <cole...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/2508bc7c Stats: 25 lines in 5 files changed: 17 ins; 0 del; 8 mod 8257140: Crash in JvmtiTagMap::flush_object_free_events() Reviewed-by: sspitsyn, kbarrett ------------- PR: https://git.openjdk.java.net/jdk/pull/1539
