RFR: 8368727: CDS custom loader support causes asserts during class unloading

[Ioi Lam]

On Mon, 29 Sep 2025 02:26:58 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> src/hotspot/share/classfile/systemDictionaryShared.cpp line 177:
>> 
>>> 175:   // No longer holding SharedDictionary_lock
>>> 176:   // No need to lock, as <ik> can be held only by a single thread.
>>> 177:   loader_data->add_class(ik);
>> 
>> Are the comments pertaining to the `add_class` call?
>
> Why not just move this to after the successful `load_shared_class` below? It is very hard to see the complete call sequence to when `restore_unshareable_info` gets called, to know that moving it there makes sense.

The comment is about all that could happen to `ik` after the current thread have gotten exclusive ownership of `ik`.  I.e., no other thread will modify the contents of `ik` or store `ik` into a `ClassLoaderData`.

The `loader_data->add_class(ik)` for all other shared classes are done inside `restore_unshareable_info()`, so we should do the same thing in this case. This means the same sequence of actions will happen (e.g.,  `loader_data->add_class(ik)` happens before the the Java mirror is created.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27511#discussion_r2393426301