RFR 8171971: Fix timing bug in JVM management of package export lists

[Alan Bateman]

On 18/01/2017 15:05, harold seigel wrote:
> Hi,
>
> Please review this fix for the package export timing holes discussed 
> in JDK-8171971.  The fix reduces the number of PackageEntry fields 
> that are used to maintain a package's export state and uses the 
> Module_lock to protect all access to these fields.
>
> Also, in cases where a package transitions from having qualified 
> exports to being unqualifiedly exported, it fixes the cleanup of its 
> qualified export list by removing the _exported_pending_delete field 
> and using just is_unqual_exported() to determine when the qualified 
> exports list can be purged (at a safepoint).
>
> Open Webrev: http://cr.openjdk.java.net/~hseigel/bug_8171971/webrev/
Does this mean that everyone doing an access check needs Module_lock?

BTW: There is no API support for changing a module to export a package 
unconditionally. Only qualified exports can be added at runtime. Just 
mentioning in case this helps to consider options that would avoid 
contention on the mutex during access checks.