K 10
svn:author
V 3
kib
K 8
svn:date
V 27
2012-12-10T20:44:09.664324Z
K 7
svn:log
V 494
Do not yield while owning a mutex.  The Giant reacquire in the
kern_yield() is problematic than.

The owned mutex is the mount interlock, and it is in fact not needed
to guarantee the stability of the mount list of active vnodes, so fix
the the issue by only taking the mount interlock for MNT_REF and
MNT_REL operations.

While there, augment the unconditional yield by some amount of
spinning [1].

Reported and tested by:	pho
Reviewed by:	attilio
Submitted by:	attilio [1]
MFC after:	3 days

END