tree b3e3b61af6bd079989a1bf5259daaa8006af32d4
parent 388c6e273018c753d7822d09d7cda0826f0c32ed
author Hiroshi Yamauchi <yamauchi@google.com> 1400731823 -0700
committer Hiroshi Yamauchi <yamauchi@google.com> 1400732357 -0700

Add a read barrier for weak roots in monitors.

A weak root requires a read barrier for the to-space invariant to hold
because the object pointed to by a weak root can't be marked/forwarded
like the one pointed to by a strong root (GC does not know if it's
alive or not at that point) and because, without a read barrier, a
mutator could access it and obtain a from-space reference, which would
violate the to-space invariant.

TODO: do similar for the other types of weak roots.

Bug: 12687968
Change-Id: I563a0fa4f875e0c21ac96f57696959454e13b15a