This commit increases debug information in the case where the grace-period
kthread is being prevented from running by dumping that kthread's stack.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Split into prior commit and this commit, as suggested by
  Josh Triplett. ]
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>