RFR (XS): 8138922: StubCodeDesc constructor publishes partially-constructed objects on StubCodeDesc::_list
vladimir.x.ivanov at oracle.com
Wed Feb 10 18:13:53 UTC 2016
StubCodeDesc keeps a list of all descriptors rooted at
StubCodeDesc::_list by placing newly instantiated objects there at the
end of the constructor. Unfortunately, it doesn't guarantee that only
fully-constructed objects are visible, because compiler (or HW) can
reorder the stores.
Since method handle adapters are generated on demand when j.l.i
framework is initialized, it's possible there are readers iterating over
the list at the moment. It's not a problem per se until everybody sees a
consistent view of the list.
The fix is to insert a StoreStore barrier before registering an object
on the list.
(I also considered moving MH adapter allocation to VM initialization
phase before anybody reads the list, but it's non-trivial since
MethodHandles::generate_adapters() has a number of implicit dependencies.)
Testing: manual (verified StubCodeMark assembly), JPRT
More information about the hotspot-dev