rcu: Add WARN_ON_ONCE() consistency checks covering state transitions

o Verify that qsmask bits stay clear through GP
  initialization.

o Verify that cpu_quiet_msk_finish() is never invoked unless
  there actually is an RCU grace period in progress.

o Verify that all internal-node rcu_node structures have empty
  blocked_tasks[] lists.

o Verify that child rcu_node structure's bits remain clear after
  acquiring parent's lock.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
LKML-Reference: <12532926191947-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>