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. */
rcu_cblist_n_cbs(struct rcu_cblist * rclp)13 static inline long rcu_cblist_n_cbs(struct rcu_cblist *rclp)
14 {
15 	return READ_ONCE(rclp->len);
16 }
17 
18 long rcu_segcblist_get_seglen(struct rcu_segcblist *rsclp, int seg);
19 
20 /* Return number of callbacks in segmented callback list by summing seglen. */
21 long rcu_segcblist_n_segment_cbs(struct rcu_segcblist *rsclp);
22 
23 void rcu_cblist_init(struct rcu_cblist *rclp);
24 void rcu_cblist_enqueue(struct rcu_cblist *rclp, struct rcu_head *rhp);
25 void rcu_cblist_flush_enqueue(struct rcu_cblist *drclp,
26 			      struct rcu_cblist *srclp,
27 			      struct rcu_head *rhp);
28 struct rcu_head *rcu_cblist_dequeue(struct rcu_cblist *rclp);
29 
30 /*
31  * Is the specified rcu_segcblist structure empty?
32  *
33  * But careful!  The fact that the ->head field is NULL does not
34  * necessarily imply that there are no callbacks associated with
35  * this structure.  When callbacks are being invoked, they are
36  * removed as a group.  If callback invocation must be preempted,
37  * the remaining callbacks will be added back to the list.  Either
38  * way, the counts are updated later.
39  *
40  * So it is often the case that rcu_segcblist_n_cbs() should be used
41  * instead.
42  */
rcu_segcblist_empty(struct rcu_segcblist * rsclp)43 static inline bool rcu_segcblist_empty(struct rcu_segcblist *rsclp)
44 {
45 	return !READ_ONCE(rsclp->head);
46 }
47 
48 /* Return number of callbacks in segmented callback list. */
rcu_segcblist_n_cbs(struct rcu_segcblist * rsclp)49 static inline long rcu_segcblist_n_cbs(struct rcu_segcblist *rsclp)
50 {
51 #ifdef CONFIG_RCU_NOCB_CPU
52 	return atomic_long_read(&rsclp->len);
53 #else
54 	return READ_ONCE(rsclp->len);
55 #endif
56 }
57 
rcu_segcblist_set_flags(struct rcu_segcblist * rsclp,int flags)58 static inline void rcu_segcblist_set_flags(struct rcu_segcblist *rsclp,
59 					   int flags)
60 {
61 	WRITE_ONCE(rsclp->flags, rsclp->flags | flags);
62 }
63 
rcu_segcblist_clear_flags(struct rcu_segcblist * rsclp,int flags)64 static inline void rcu_segcblist_clear_flags(struct rcu_segcblist *rsclp,
65 					     int flags)
66 {
67 	WRITE_ONCE(rsclp->flags, rsclp->flags & ~flags);
68 }
69 
rcu_segcblist_test_flags(struct rcu_segcblist * rsclp,int flags)70 static inline bool rcu_segcblist_test_flags(struct rcu_segcblist *rsclp,
71 					    int flags)
72 {
73 	return READ_ONCE(rsclp->flags) & flags;
74 }
75 
76 /*
77  * Is the specified rcu_segcblist enabled, for example, not corresponding
78  * to an offline CPU?
79  */
rcu_segcblist_is_enabled(struct rcu_segcblist * rsclp)80 static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)
81 {
82 	return rcu_segcblist_test_flags(rsclp, SEGCBLIST_ENABLED);
83 }
84 
85 /*
86  * Is the specified rcu_segcblist NOCB offloaded (or in the middle of the
87  * [de]offloading process)?
88  */
rcu_segcblist_is_offloaded(struct rcu_segcblist * rsclp)89 static inline bool rcu_segcblist_is_offloaded(struct rcu_segcblist *rsclp)
90 {
91 	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
92 	    rcu_segcblist_test_flags(rsclp, SEGCBLIST_LOCKING))
93 		return true;
94 
95 	return false;
96 }
97 
rcu_segcblist_completely_offloaded(struct rcu_segcblist * rsclp)98 static inline bool rcu_segcblist_completely_offloaded(struct rcu_segcblist *rsclp)
99 {
100 	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
101 	    !rcu_segcblist_test_flags(rsclp, SEGCBLIST_RCU_CORE))
102 		return true;
103 
104 	return false;
105 }
106 
107 /*
108  * Are all segments following the specified segment of the specified
109  * rcu_segcblist structure empty of callbacks?  (The specified
110  * segment might well contain callbacks.)
111  */
rcu_segcblist_restempty(struct rcu_segcblist * rsclp,int seg)112 static inline bool rcu_segcblist_restempty(struct rcu_segcblist *rsclp, int seg)
113 {
114 	return !READ_ONCE(*READ_ONCE(rsclp->tails[seg]));
115 }
116 
117 /*
118  * Is the specified segment of the specified rcu_segcblist structure
119  * empty of callbacks?
120  */
rcu_segcblist_segempty(struct rcu_segcblist * rsclp,int seg)121 static inline bool rcu_segcblist_segempty(struct rcu_segcblist *rsclp, int seg)
122 {
123 	if (seg == RCU_DONE_TAIL)
124 		return &rsclp->head == rsclp->tails[RCU_DONE_TAIL];
125 	return rsclp->tails[seg - 1] == rsclp->tails[seg];
126 }
127 
128 void rcu_segcblist_inc_len(struct rcu_segcblist *rsclp);
129 void rcu_segcblist_add_len(struct rcu_segcblist *rsclp, long v);
130 void rcu_segcblist_init(struct rcu_segcblist *rsclp);
131 void rcu_segcblist_disable(struct rcu_segcblist *rsclp);
132 void rcu_segcblist_offload(struct rcu_segcblist *rsclp, bool offload);
133 bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp);
134 bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp);
135 struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp);
136 struct rcu_head *rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp);
137 bool rcu_segcblist_nextgp(struct rcu_segcblist *rsclp, unsigned long *lp);
138 void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
139 			   struct rcu_head *rhp);
140 bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
141 			   struct rcu_head *rhp);
142 void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
143 				    struct rcu_cblist *rclp);
144 void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
145 				    struct rcu_cblist *rclp);
146 void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp,
147 				struct rcu_cblist *rclp);
148 void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
149 				   struct rcu_cblist *rclp);
150 void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
151 				   struct rcu_cblist *rclp);
152 void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq);
153 bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq);
154 void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp,
155 			 struct rcu_segcblist *src_rsclp);
156