1/* SPDX-License-Identifier: GPL-2.0+ */
  2/*
  3 * RCU segmented callback lists, internal-to-rcu header file
  4 *
  5 * Copyright IBM Corporation, 2017
  6 *
  7 * Authors: Paul E. McKenney <paulmck@linux.ibm.com>
  8 */
  9
 10#include <linux/rcu_segcblist.h>
 11
 12/* Return number of callbacks in the specified callback list. */
 13static inline long rcu_cblist_n_cbs(struct rcu_cblist *rclp)
 14{
 15	return READ_ONCE(rclp->len);
 16}
 17
 18/* Return number of callbacks in segmented callback list by summing seglen. */
 19long rcu_segcblist_n_segment_cbs(struct rcu_segcblist *rsclp);
 20
 21void rcu_cblist_init(struct rcu_cblist *rclp);
 22void rcu_cblist_enqueue(struct rcu_cblist *rclp, struct rcu_head *rhp);
 23void rcu_cblist_flush_enqueue(struct rcu_cblist *drclp,
 24			      struct rcu_cblist *srclp,
 25			      struct rcu_head *rhp);
 26struct rcu_head *rcu_cblist_dequeue(struct rcu_cblist *rclp);
 27
 28/*
 29 * Is the specified rcu_segcblist structure empty?
 30 *
 31 * But careful!  The fact that the ->head field is NULL does not
 32 * necessarily imply that there are no callbacks associated with
 33 * this structure.  When callbacks are being invoked, they are
 34 * removed as a group.  If callback invocation must be preempted,
 35 * the remaining callbacks will be added back to the list.  Either
 36 * way, the counts are updated later.
 37 *
 38 * So it is often the case that rcu_segcblist_n_cbs() should be used
 39 * instead.
 40 */
 41static inline bool rcu_segcblist_empty(struct rcu_segcblist *rsclp)
 42{
 43	return !READ_ONCE(rsclp->head);
 44}
 45
 46/* Return number of callbacks in segmented callback list. */
 47static inline long rcu_segcblist_n_cbs(struct rcu_segcblist *rsclp)
 48{
 49#ifdef CONFIG_RCU_NOCB_CPU
 50	return atomic_long_read(&rsclp->len);
 51#else
 52	return READ_ONCE(rsclp->len);
 53#endif
 54}
 55
 56static inline void rcu_segcblist_set_flags(struct rcu_segcblist *rsclp,
 57					   int flags)
 58{
 59	rsclp->flags |= flags;
 60}
 61
 62static inline void rcu_segcblist_clear_flags(struct rcu_segcblist *rsclp,
 63					     int flags)
 64{
 65	rsclp->flags &= ~flags;
 66}
 67
 68static inline bool rcu_segcblist_test_flags(struct rcu_segcblist *rsclp,
 69					    int flags)
 70{
 71	return READ_ONCE(rsclp->flags) & flags;
 72}
 73
 74/*
 75 * Is the specified rcu_segcblist enabled, for example, not corresponding
 76 * to an offline CPU?
 77 */
 78static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)
 79{
 80	return rcu_segcblist_test_flags(rsclp, SEGCBLIST_ENABLED);
 81}
 82
 83/* Is the specified rcu_segcblist offloaded, or is SEGCBLIST_SOFTIRQ_ONLY set? */
 84static inline bool rcu_segcblist_is_offloaded(struct rcu_segcblist *rsclp)
 85{
 86	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
 87	    !rcu_segcblist_test_flags(rsclp, SEGCBLIST_SOFTIRQ_ONLY))
 88		return true;
 89
 90	return false;
 91}
 92
 93static inline bool rcu_segcblist_completely_offloaded(struct rcu_segcblist *rsclp)
 94{
 95	int flags = SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP | SEGCBLIST_OFFLOADED;
 96
 97	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) && (rsclp->flags & flags) == flags)
 98		return true;
 99
100	return false;
101}
102
103/*
104 * Are all segments following the specified segment of the specified
105 * rcu_segcblist structure empty of callbacks?  (The specified
106 * segment might well contain callbacks.)
107 */
108static inline bool rcu_segcblist_restempty(struct rcu_segcblist *rsclp, int seg)
109{
110	return !READ_ONCE(*READ_ONCE(rsclp->tails[seg]));
111}
112
113/*
114 * Is the specified segment of the specified rcu_segcblist structure
115 * empty of callbacks?
116 */
117static inline bool rcu_segcblist_segempty(struct rcu_segcblist *rsclp, int seg)
118{
119	if (seg == RCU_DONE_TAIL)
120		return &rsclp->head == rsclp->tails[RCU_DONE_TAIL];
121	return rsclp->tails[seg - 1] == rsclp->tails[seg];
122}
123
124void rcu_segcblist_inc_len(struct rcu_segcblist *rsclp);
125void rcu_segcblist_add_len(struct rcu_segcblist *rsclp, long v);
126void rcu_segcblist_init(struct rcu_segcblist *rsclp);
127void rcu_segcblist_disable(struct rcu_segcblist *rsclp);
128void rcu_segcblist_offload(struct rcu_segcblist *rsclp, bool offload);
129bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp);
130bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp);
131struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp);
132struct rcu_head *rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp);
133bool rcu_segcblist_nextgp(struct rcu_segcblist *rsclp, unsigned long *lp);
134void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
135			   struct rcu_head *rhp);
136bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
137			   struct rcu_head *rhp);
138void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
139				    struct rcu_cblist *rclp);
140void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
141				    struct rcu_cblist *rclp);
142void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp,
143				struct rcu_cblist *rclp);
144void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
145				   struct rcu_cblist *rclp);
146void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
147				   struct rcu_cblist *rclp);
148void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq);
149bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq);
150void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp,
151			 struct rcu_segcblist *src_rsclp);