Ok, in general, for concurrent code, it's either not an issue or it's an issue.  Putting comments in code like these just create doubt in the reader.  Alternatively, comments describing what's going on and why it should be ok would be more beneficial.

So like, "It's possible that our task failed while this action was running and has given up all of the locks.  This shouldn't be a problem because it should have sequenced the insertion of the metadata such that it happens after the index is generated so even if this populates metadata, it will be consistent."