Comment 2 for bug 1268710

Commits 229d6eb7478904ad5228ea6a6bd3fa67053e2198, 5338e756b46022ef748b969cfc56f9053fe46b2e, and bcc6a2d83b6cd64322ab63600e2af6db103c5d49 all address various safepoint deadlock scenarios. This particular deadlock scenario is one of them, but due to the lack of a "thread apply all backtrace" to obtain the C backtraces, I can't tell which of two possible deadlocks was hit in this case.