The MigrationDestinationManager checks-out a session and then proceeds executing the recipient logic while that session is checked-out.

The execution logic at some point reaches to a call to waitForWriteConcern which runs with the session still checked-out.

Because the JournalFlusher wait is non-interruptible (and also because SERVER-40081 prohibits waitForWriteConcern while having a session checked-out), this this causes a three-thread deadlock with the replication coordinator:

• T1: MigrationDestinationManager has a session checked-out and is waiting on waitForWriteConcern, which in turn is blocked on JournalFlusher::waitForJournalFlush
• T2: The JournalFlusher is waiting on a MODE_IX RSM lock, which is held in MODE_X by ReplCoord-3
• T3: ReplCoord-3, while holding the RSM lock in MODE_X, is killing sessions by calling invalidateSessionsForStepdown and this is blocked on the session checked-out by T1