rcu: Add lockdep_assert_irqs_disabled() to rcu_sched_clock_irq() and callees

[ Upstream commit a649d25dcc671a33b9cc3176411920fdc5fbd98e ]

This commit adds a number of lockdep_assert_irqs_disabled() calls
to rcu_sched_clock_irq() and a number of the functions that it calls.
The point of this is to help track down a situation where lockdep appears
to be insisting that interrupts are enabled within these functions, which
should only ever be invoked from the scheduling-clock interrupt handler.

Link: https://lore.kernel.org/lkml/20201111133813.GA81547@elver.google.com/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

kernel/rcu/tree_plugin.h

@@ -682,6 +682,7 @@ static void rcu_flavor_sched_clock_irq(int user)
 {
 	struct task_struct *t = current;
 
+	lockdep_assert_irqs_disabled();
 	if (user || rcu_is_cpu_rrupt_from_idle()) {
 		rcu_note_voluntary_context_switch(current);
 	}