All to often we come across this issue. There are a number of bugs that are likely fixed by doing this change - even if it isn't academically perfect.
On Sep 13, 2011, at 9:31 AM, Peter Rajnoha wrote:
If a dm device is being opened in parallel while we're
trying to remove it, we'll end up with an error that
the device is busy. This is a legitimate error, but
with udev in play and asynchronous events generated
as a result of using the WATCH udev rule, we can get
into a situation where such failure is very unpleasant.
Let's try the removal a few times then. Though this is
not a complete solution to the problem, let's use this
until we have one.