Deadlocks under extremely rare race conditions

Synopsis
We have discovered a very rare race condition which results in a deadlocked process and consequently queries that do not end. Statements potentially affected by this bug are both DML and DQL; however based on empirical evidence (one occurrence in almost a year) we expect it to occur extremely rare.

Workaround
There is no workaround for this bug, apart from simply aborting the affected statement and running it again.