GaloisInc/halvm-ghc — pull request #4 by TomMD (2014-06-13 16:07:48+00:00)
Title: Check for pending schedules after setting the trigger event.

The bug this fixes is hard to detect on modern hardware unless it is
under particularly high load that presumably causes wonky VM scheduling.

Disclaimer:

I am unclear enough on Xen signaling to be absolutely sure this
eliminates the possible window for dropped signals instead of merely
shrinking the window.