1/*
  2 * RCU segmented callback lists, internal-to-rcu header file
  3 *
  4 * This program is free software; you can redistribute it and/or modify
  5 * it under the terms of the GNU General Public License as published by
  6 * the Free Software Foundation; either version 2 of the License, or
  7 * (at your option) any later version.
  8 *
  9 * This program is distributed in the hope that it will be useful,
 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12 * GNU General Public License for more details.
 13 *
 14 * You should have received a copy of the GNU General Public License
 15 * along with this program; if not, you can access it online at
 16 * http://www.gnu.org/licenses/gpl-2.0.html.
 17 *
 18 * Copyright IBM Corporation, 2017
 19 *
 20 * Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 21 */
 22
 23#include <linux/rcu_segcblist.h>
 24
 25/*
 26 * Account for the fact that a previously dequeued callback turned out
 27 * to be marked as lazy.
 28 */
 29static inline void rcu_cblist_dequeued_lazy(struct rcu_cblist *rclp)
 30{
 31	rclp->len_lazy--;
 32}
 33
 34void rcu_cblist_init(struct rcu_cblist *rclp);
 35struct rcu_head *rcu_cblist_dequeue(struct rcu_cblist *rclp);
 36
 37/*
 38 * Is the specified rcu_segcblist structure empty?
 39 *
 40 * But careful!  The fact that the ->head field is NULL does not
 41 * necessarily imply that there are no callbacks associated with
 42 * this structure.  When callbacks are being invoked, they are
 43 * removed as a group.  If callback invocation must be preempted,
 44 * the remaining callbacks will be added back to the list.  Either
 45 * way, the counts are updated later.
 46 *
 47 * So it is often the case that rcu_segcblist_n_cbs() should be used
 48 * instead.
 49 */
 50static inline bool rcu_segcblist_empty(struct rcu_segcblist *rsclp)
 51{
 52	return !rsclp->head;
 53}
 54
 55/* Return number of callbacks in segmented callback list. */
 56static inline long rcu_segcblist_n_cbs(struct rcu_segcblist *rsclp)
 57{
 58	return READ_ONCE(rsclp->len);
 59}
 60
 61/* Return number of lazy callbacks in segmented callback list. */
 62static inline long rcu_segcblist_n_lazy_cbs(struct rcu_segcblist *rsclp)
 63{
 64	return rsclp->len_lazy;
 65}
 66
 67/* Return number of lazy callbacks in segmented callback list. */
 68static inline long rcu_segcblist_n_nonlazy_cbs(struct rcu_segcblist *rsclp)
 69{
 70	return rsclp->len - rsclp->len_lazy;
 71}
 72
 73/*
 74 * Is the specified rcu_segcblist enabled, for example, not corresponding
 75 * to an offline or callback-offloaded CPU?
 76 */
 77static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)
 78{
 79	return !!rsclp->tails[RCU_NEXT_TAIL];
 80}
 81
 82/*
 83 * Are all segments following the specified segment of the specified
 84 * rcu_segcblist structure empty of callbacks?  (The specified
 85 * segment might well contain callbacks.)
 86 */
 87static inline bool rcu_segcblist_restempty(struct rcu_segcblist *rsclp, int seg)
 88{
 89	return !*rsclp->tails[seg];
 90}
 91
 92/*
 93 * Interim function to return rcu_segcblist head pointer.  Longer term, the
 94 * rcu_segcblist will be used more pervasively, removing the need for this
 95 * function.
 96 */
 97static inline struct rcu_head *rcu_segcblist_head(struct rcu_segcblist *rsclp)
 98{
 99	return rsclp->head;
100}
101
102/*
103 * Interim function to return rcu_segcblist head pointer.  Longer term, the
104 * rcu_segcblist will be used more pervasively, removing the need for this
105 * function.
106 */
107static inline struct rcu_head **rcu_segcblist_tail(struct rcu_segcblist *rsclp)
108{
109	WARN_ON_ONCE(rcu_segcblist_empty(rsclp));
110	return rsclp->tails[RCU_NEXT_TAIL];
111}
112
113void rcu_segcblist_init(struct rcu_segcblist *rsclp);
114void rcu_segcblist_disable(struct rcu_segcblist *rsclp);
115bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp);
116bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp);
117struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp);
118struct rcu_head *rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp);
119void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
120			   struct rcu_head *rhp, bool lazy);
121bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
122			   struct rcu_head *rhp, bool lazy);
123void rcu_segcblist_extract_count(struct rcu_segcblist *rsclp,
124				 struct rcu_cblist *rclp);
125void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
126				    struct rcu_cblist *rclp);
127void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
128				    struct rcu_cblist *rclp);
129void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp,
130				struct rcu_cblist *rclp);
131void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
132				   struct rcu_cblist *rclp);
133void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
134				   struct rcu_cblist *rclp);
135void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq);
136bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq);
137bool rcu_segcblist_future_gp_needed(struct rcu_segcblist *rsclp,
138				    unsigned long seq);
139void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp,
140			 struct rcu_segcblist *src_rsclp);