On Thu, 14 Oct 2021 21:58:42 GMT, Coleen Phillimore <cole...@openjdk.org> wrote:
>> "Since you remove entries on unloading, I don't see any reason to have any >> concurrent cleanup." >> Thank you, that is true. The only concurrent work required will be to grow >> the table. >> >> "You do however need in the lookup code, some code that doesn't find the >> InstanceKlass if !ik->is_loader_alive()" >> >> A precondition is that the code doing the lookup hold the >> ClassLoaderDataGraph_lock or is at a safepoint. Is that still the case? >> Would not purge_unloaded() take out the InstanceKlass from the table, as >> part of unloading, before !ik->is_loader_alive() is published to the outside >> world? > > Ok, I see - grow the table. > > I'm not sure if you need to ask ik->is_loader_alive() or not, but I think you > do. The InstanceKlass is removed from your table during class unloading but > before that during concurrent class unloading, the class might not be alive > while you look at it and concurrent class unloading hasn't gotten around to > removing it yet. Since you save classes regardless of CLD, you have to check > if it's alive. See classLoaderDataGraph.cpp ClassLoaderDataGraphIterator for > example. The CLDG_lock only keeps the graph from not getting modified, but > the classes in it might be dead. That said, I don't see where you return an InstanceKlass in the table, which would need this check. Not in class_unloading_do because this follows the _unloading list. ------------- PR: https://git.openjdk.java.net/jdk/pull/4731
