Convert P_COWINPROGRESS to per-thread lock-less flag..

[John Baldwin]

As part of the proc locking, I have a patch that converts the
per-process P_COWINPROGRESS flag to a per-thread flag instead.
The per-thread flag is a TDP_COWINPROGRESS flag stored in
td_pflags which does not require any locks.  This removes the
last user of p_flag that does not use the proc lock.  Are there
any problems with making this flag per-thread instead of
per-process?

http://www.FreeBSD.org/~jhb/patches/cow.patch

-- 

John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/