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 /* Return number of callbacks in segmented callback list by summing seglen. */
19 long rcu_segcblist_n_segment_cbs(struct rcu_segcblist *rsclp);
20 
21 void rcu_cblist_init(struct rcu_cblist *rclp);
22 void rcu_cblist_enqueue(struct rcu_cblist *rclp, struct rcu_head *rhp);
23 void rcu_cblist_flush_enqueue(struct rcu_cblist *drclp,
24 			      struct rcu_cblist *srclp,
25 			      struct rcu_head *rhp);
26 struct 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  */
rcu_segcblist_empty(struct rcu_segcblist * rsclp)41 static 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. */
rcu_segcblist_n_cbs(struct rcu_segcblist * rsclp)47 static 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 
rcu_segcblist_set_flags(struct rcu_segcblist * rsclp,int flags)56 static inline void rcu_segcblist_set_flags(struct rcu_segcblist *rsclp,
57 					   int flags)
58 {
59 	WRITE_ONCE(rsclp->flags, rsclp->flags | flags);
60 }
61 
rcu_segcblist_clear_flags(struct rcu_segcblist * rsclp,int flags)62 static inline void rcu_segcblist_clear_flags(struct rcu_segcblist *rsclp,
63 					     int flags)
64 {
65 	WRITE_ONCE(rsclp->flags, rsclp->flags & ~flags);
66 }
67 
rcu_segcblist_test_flags(struct rcu_segcblist * rsclp,int flags)68 static 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  */
rcu_segcblist_is_enabled(struct rcu_segcblist * rsclp)78 static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)
79 {
80 	return rcu_segcblist_test_flags(rsclp, SEGCBLIST_ENABLED);
81 }
82 
83 /*
84  * Is the specified rcu_segcblist NOCB offloaded (or in the middle of the
85  * [de]offloading process)?
86  */
rcu_segcblist_is_offloaded(struct rcu_segcblist * rsclp)87 static inline bool rcu_segcblist_is_offloaded(struct rcu_segcblist *rsclp)
88 {
89 	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
90 	    rcu_segcblist_test_flags(rsclp, SEGCBLIST_LOCKING))
91 		return true;
92 
93 	return false;
94 }
95 
rcu_segcblist_completely_offloaded(struct rcu_segcblist * rsclp)96 static inline bool rcu_segcblist_completely_offloaded(struct rcu_segcblist *rsclp)
97 {
98 	if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
99 	    !rcu_segcblist_test_flags(rsclp, SEGCBLIST_RCU_CORE))
100 		return true;
101 
102 	return false;
103 }
104 
105 /*
106  * Are all segments following the specified segment of the specified
107  * rcu_segcblist structure empty of callbacks?  (The specified
108  * segment might well contain callbacks.)
109  */
rcu_segcblist_restempty(struct rcu_segcblist * rsclp,int seg)110 static inline bool rcu_segcblist_restempty(struct rcu_segcblist *rsclp, int seg)
111 {
112 	return !READ_ONCE(*READ_ONCE(rsclp->tails[seg]));
113 }
114 
115 /*
116  * Is the specified segment of the specified rcu_segcblist structure
117  * empty of callbacks?
118  */
rcu_segcblist_segempty(struct rcu_segcblist * rsclp,int seg)119 static inline bool rcu_segcblist_segempty(struct rcu_segcblist *rsclp, int seg)
120 {
121 	if (seg == RCU_DONE_TAIL)
122 		return &rsclp->head == rsclp->tails[RCU_DONE_TAIL];
123 	return rsclp->tails[seg - 1] == rsclp->tails[seg];
124 }
125 
126 void rcu_segcblist_inc_len(struct rcu_segcblist *rsclp);
127 void rcu_segcblist_add_len(struct rcu_segcblist *rsclp, long v);
128 void rcu_segcblist_init(struct rcu_segcblist *rsclp);
129 void rcu_segcblist_disable(struct rcu_segcblist *rsclp);
130 void rcu_segcblist_offload(struct rcu_segcblist *rsclp, bool offload);
131 bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp);
132 bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp);
133 struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp);
134 struct rcu_head *rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp);
135 bool rcu_segcblist_nextgp(struct rcu_segcblist *rsclp, unsigned long *lp);
136 void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
137 			   struct rcu_head *rhp);
138 bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
139 			   struct rcu_head *rhp);
140 void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
141 				    struct rcu_cblist *rclp);
142 void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
143 				    struct rcu_cblist *rclp);
144 void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp,
145 				struct rcu_cblist *rclp);
146 void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
147 				   struct rcu_cblist *rclp);
148 void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
149 				   struct rcu_cblist *rclp);
150 void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq);
151 bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq);
152 void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp,
153 			 struct rcu_segcblist *src_rsclp);
154