pg_stop_backup running for 2h10m?

Hi,

I used omnipitr to launch a base backup, but I fumbled a couple of things, so I Ctrl+C'd *once* the console where I had
omnipitr-backup-masterrunning. omnipitr-backup-master correctly launched pg_stop_backup, but pg_stop_backup has been
activefor 2h10 minutes, as reported by pg_stat_activity. 

According to the docs, pg_stop_backup wants to archive all xlogs before returning, but xlogs aren't being added to the
backupdirectory. 

What could be preventing pg_stop_backup from returning?

Thanks!
François Beausoleil