This commit, which was subsequently reverted, caused a test hang in CollectionRangeDeleter::DeleteNotification::waitStatus: https://github.com/mongodb/mongo/commit/344bf6e257e1427bc594bacac3f5983c2bdeaacf The hang can be seen in this build https://evergreen.mongodb.com/task/mongodb_mongo_master_enterprise_rhel_62_64_bit_slow1_344bf6e257e1427bc594bacac3f5983c2bdeaacf_17_07_07_12_44_23 and in the linked BF-5886. The CollectionRangeDeleter functions called in moveChunk were changed in the above commit. It seems to have unwittingly surfaced a bug.

The original sequence of range deleter calls was

• DeleteNotification notification = cleanUpRange()
• notification.abandon()
• waitForClean()

The failed commit did

• DeleteNotification notification = cleanUpRange()
• notification.waitStatus() <-- hangs non-deterministically, though frequent enough to be reproducible

There's no corresponding "Finished deleting mr_during_migrate.coll range ...." message after the donor finishes the migration and starts waiting in the hung test logs. And one of the thread dumps has CollectionRangeDeleter::DeleteNotification::waitStatus in it.