rcu: Clear ->rcu_read_unlock_special only once

In rcu_preempt_deferred_qs_irqrestore(), ->rcu_read_unlock_special is
cleared one piece at a time.  Given that the "if" statements in this
function use the copy in "special", this commit removes the clearing
of the individual pieces in favor of clearing ->rcu_read_unlock_special
in one go just after it has been determined to be non-zero.

Signed-off-by: Lai Jiangshan <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

Author: Lai Jiangshan

kernel/rcu/tree_plugin.h

@@ -444,34 +444,21 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
 		local_irq_restore(flags);
 		return;
 	}
-	t->rcu_read_unlock_special.b.exp_hint = false;
-	t->rcu_read_unlock_special.b.deferred_qs = false;
-	if (special.b.need_qs) {
+	t->rcu_read_unlock_special.s = 0;
+	if (special.b.need_qs)
 		rcu_qs();
-		t->rcu_read_unlock_special.b.need_qs = false;
-		if (!t->rcu_read_unlock_special.s && !rdp->exp_deferred_qs) {
-			local_irq_restore(flags);
-			return;
-		}
-	}
 
 	/*
 	 * Respond to a request by an expedited grace period for a
 	 * quiescent state from this CPU.  Note that requests from
 	 * tasks are handled when removing the task from the
 	 * blocked-tasks list below.
 	 */
-	if (rdp->exp_deferred_qs) {
+	if (rdp->exp_deferred_qs)
 		rcu_report_exp_rdp(rdp);
-		if (!t->rcu_read_unlock_special.s) {
-			local_irq_restore(flags);
-			return;
-		}
-	}
 
 	/* Clean up if blocked during RCU read-side critical section. */
 	if (special.b.blocked) {
-		t->rcu_read_unlock_special.b.blocked = false;
 
 		/*
 		 * Remove this task from the list it blocked on.  The task