rcu/exp: Fix check for idle context in rcu_exp_handler

For PREEMPT_RCU, the rcu_exp_handler() function checks
whether the current CPU is in idle, by calling
rcu_dynticks_curr_cpu_in_eqs(). However, rcu_exp_handler()
is called in IPI handler context. So, it should be checking
the idle context using rcu_is_cpu_rrupt_from_idle(). Fix this
by using rcu_is_cpu_rrupt_from_idle() instead of
rcu_dynticks_curr_cpu_in_eqs(). Non-preempt configuration
already uses the correct check.

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Author: Neeraj Upadhyay

kernel/rcu/tree_exp.h

@@ -656,7 +656,7 @@ static void rcu_exp_handler(void *unused)
 	 */
 	if (!depth) {
 		if (!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)) ||
-		    rcu_dynticks_curr_cpu_in_eqs()) {
+		    rcu_is_cpu_rrupt_from_idle()) {
 			rcu_report_exp_rdp(rdp);
 		} else {
 			WRITE_ONCE(rdp->cpu_no_qs.b.exp, true);