On Thu, 1 Sep 2022 06:42:06 GMT, Ioi Lam <ik...@openjdk.org> wrote: >> src/hotspot/share/classfile/protectionDomainCache.hpp line 33: >> >>> 31: >>> 32: // The ProtectionDomainCacheTable maps all >>> java.security.ProtectionDomain objects that are >>> 33: // registered by DictionaryEntry::add_protection_domain() to a unique >>> WeakHandle. >> >> Now that I understand what this table does, this comment is confusing to me. >> The table maps each PD to itself (using the WeakHandle as the actual key and >> value) as a means to track which PDs have been seen/registered. I would >> describe it thus: >> >> // The ProtectionDomainCacheTable records all of the >> java.security.ProtectionDomain instances that have >> // been registered by DictionaryEntry::add_protection_domain(). We use a >> hashtable to >> map each PD >> // instance to itself (using WeakHandles) to allow for fast lookup. > > “Mapping to itself” is how this table works internally. I am not sure if this > information is useful here. But the purpose of this table is really to keep > track of all PDs that have been registered and not yet garbage collected.
"mapping to itself" is more useful than "mapping ... to a unique Weakhandle" - which is even more of an internal implementation detail. I found the use of this table very hard to discern based on the internal use of the hashtable, as there is no real mapping operation - we simply track if a PD has been seen or not. The use of the hashtable is purely for lookup convenience - we could instead have a linked-list of PD's that we traverse for lookup. So perhaps we drop my second sentence above, and move it to where the hashtable itself is declared? ------------- PR: https://git.openjdk.org/jdk/pull/10043
