xref: /linux/kernel/rcu/rcu_segcblist.h (revision 39f75da7bcc829ddc4d40bb60d0e95520de7898b) 
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. */
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  */
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. */
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 
56 static inline void rcu_segcblist_set_flags(struct rcu_segcblist *rsclp,
57 					   int flags)
58 {
59 	rsclp->flags |= flags;
60 }
61 
62 static inline void rcu_segcblist_clear_flags(struct rcu_segcblist *rsclp,
63 					     int flags)
64 {
65 	rsclp->flags &= ~flags;
66 }
67 
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  */
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 /* Is the specified rcu_segcblist offloaded, or is SEGCBLIST_SOFTIRQ_ONLY set? */
84 static 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 
93 static 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  */
108 static 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  */
117 static 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 
124 void rcu_segcblist_inc_len(struct rcu_segcblist *rsclp);
125 void rcu_segcblist_add_len(struct rcu_segcblist *rsclp, long v);
126 void rcu_segcblist_init(struct rcu_segcblist *rsclp);
127 void rcu_segcblist_disable(struct rcu_segcblist *rsclp);
128 void rcu_segcblist_offload(struct rcu_segcblist *rsclp, bool offload);
129 bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp);
130 bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp);
131 struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp);
132 struct rcu_head *rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp);
133 bool rcu_segcblist_nextgp(struct rcu_segcblist *rsclp, unsigned long *lp);
134 void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
135 			   struct rcu_head *rhp);
136 bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
137 			   struct rcu_head *rhp);
138 void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
139 				    struct rcu_cblist *rclp);
140 void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
141 				    struct rcu_cblist *rclp);
142 void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp,
143 				struct rcu_cblist *rclp);
144 void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
145 				   struct rcu_cblist *rclp);
146 void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
147 				   struct rcu_cblist *rclp);
148 void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq);
149 bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq);
150 void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp,
151 			 struct rcu_segcblist *src_rsclp);
152