K 10
svn:author
V 5
shurd
K 8
svn:date
V 27
2018-10-29T14:36:03.957781Z
K 7
svn:log
V 583
Drain grouptaskqueue of the gtask before detaching it.

taskqgroup_detach() would remove the task even if it was running or
enqueued, which could lead to panics (see D17404). With this change,
taskqgroup_detach() drains the task and sets a new flag which prevents the
task from being scheduled again.

I've added grouptask_block() and grouptask_unblock() to allow control
over the flag from other locations as well.

Reviewed by:	Jeffrey Pieper <jeffrey.e.pieper@intel.com>
MFC after:	1 week
Sponsored by:	Limelight Networks
Differential Revision:	https://reviews.freebsd.org/D17674

END