This commit adds tracing to the rcu_gp_kthread() function in order to
help trace down hangs potentially involving this kthread.
Reported-by: NClark Williams <williams@redhat.com>
Reported-by: NCarsten Emde <C.Emde@osadl.org>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>