Resource is busy, but lsof doesn't think so

Question

Occasionally, I get file (typically after they are edited by Microsoft Word) that I can not delete:

> rm -rf foo.docx
rm: M_AI_SO.docx: Resource busy

However, lsof doesn't report anything, even I run it as root:

> lsof | grep docx
>

How can I determine who is locking the file. And even more important: how can I delete it without a reboot?

Answer 1

lsof does not show all the processes when run as a normal user. Try with

sudo lsof | grep docx

See the SECURITY section of the man page