/*
 * rcuclassic.h: user-level prototype of hierarchical classic RCU.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (c) 2008 Paul E. McKenney, IBM Corporation.
 */

#define RCU_DONE_TAIL		0	/* Also RCU_WAIT head. */
#define RCU_WAIT_TAIL		1	/* Also RCU_NEXT_READY head. */
#define RCU_NEXT_READY_TAIL	2	/* Also RCU_NEXT head. */
#define RCU_NEXT_TAIL		3
#define RCU_NEXT_SIZE		4

/* Per-CPU data for Read-Copy UPdate. */
struct rcu_data {
	/* 1) quiescent-state and grace-period handling : */
	long		completed;	/* Track rsp->completed gp number */
					/*  in order to detect GP end. */
	long		gpnum;		/* Highest gp number that this CPU */
					/*  is aware of having started. */
	int		passed_quiesc;	/* User-mode/idle loop etc. */
	int		qs_pending;	/* core waits for quiesc state */
					/*  rdp->completed!=rsp->completed, */
					/*  but with less cache thrashing. */
	struct rcu_node *mynode;	/* this CPU's leaf of hierarchy */

	/* 2) batch handling */
	/*
	 * If nxtlist is not NULL, it is partitioned as follows.
	 * Any of the partitions might be empty, in which case the
	 * pointer to that partition will be equal to the pointer for
	 * the following partition.  When the list is empty, all of
	 * the nxttail elements point to nxtlist, which is NULL.
	 *
	 * [*nxttail[2], NULL = *nxttail[3]):
	 *	Entries that might have arrived after current GP ended
	 * [*nxttail[1], *nxttail[2]):
	 *	Entries known to have arrived before current GP ended
	 * [*nxttail[0], *nxttail[1]):
	 *	Entries that batch # <= ->completed - 1: waiting for current GP
	 * [nxtlist, *nxttail[0]):
	 *	Entries that batch # <= ->completed
	 *	The grace period for these entries has completed, and
	 *	the other grace-period-completed entries may be moved
	 *	here temporarily in rcu_process_callbacks().
	 */
	struct rcu_head *nxtlist;
	struct rcu_head **nxttail[RCU_NEXT_SIZE];
	long            qlen; 	 	/* # of queued callbacks */
	/* @@@ struct rcu_head *donelist;	*/
	/* @@@ struct rcu_head **donetail;	*/
	long		blimit;		/* Upper limit on a processed batch */
	int cpu;
	/* struct rcu_head barrier; */
};

/* @@@ DECLARE_PER_CPU(struct rcu_data, rcu_data); */
/* @@@ DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); */
DEFINE_PER_CPU(struct rcu_data, rcu_data);
DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);

/*
 * Increment the quiescent state "counter".
 * This used to really be a counter, but has atrophied.  The reason is
 * that we do not need to know how many quiescent states passed, just
 * if there was at least one since the start of the grace period.
 * The counter has therefore become a simple flag.
 */
static inline void rcu_qsctr_inc(int cpu)
{
	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
	rdp->passed_quiesc = 1;
}
static inline void rcu_bh_qsctr_inc(int cpu)
{
	struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
	rdp->passed_quiesc = 1;
}