rcu: Add single-element dequeue functions to rcu_segcblist

	       !rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL);

}

/*

 * Dequeue and return the first ready-to-invoke callback.  If there

 * are no ready-to-invoke callbacks, return NULL.  Disables interrupts

 * to avoid interference.  Does not protect from interference from other

 * CPUs or tasks.

 */

static inline struct rcu_head *

rcu_segcblist_dequeue(struct rcu_segcblist *rsclp)

{

	unsigned long flags;

	int i;

	struct rcu_head *rhp;

	local_irq_save(flags);

	if (!rcu_segcblist_ready_cbs(rsclp)) {

		local_irq_restore(flags);

		return NULL;

	}

	rhp = rsclp->head;

	BUG_ON(!rhp);

	rsclp->head = rhp->next;

	for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++) {

		if (rsclp->tails[i] != &rhp->next)

			break;

		rsclp->tails[i] = &rsclp->head;

	}

	smp_mb(); /* Dequeue before decrement for rcu_barrier(). */

	WRITE_ONCE(rsclp->len, rsclp->len - 1);

	local_irq_restore(flags);

	return rhp;

}

/*

 * Account for the fact that a previously dequeued callback turned out

 * to be marked as lazy.

 */

static inline void rcu_segcblist_dequeued_lazy(struct rcu_segcblist *rsclp)

{

	unsigned long flags;

	local_irq_save(flags);

	rsclp->len_lazy--;

	local_irq_restore(flags);

}

/*

 * Return a pointer to the first callback in the specified rcu_segcblist

 * structure.  This is useful for diagnostics.