Add rcu-reclaim.so library
[urcu.git] / urcu-reclaim-static.h
1 #ifndef _URCU_RECLAIM_STATIC_H
2 #define _URCU_RECLAIM_STATIC_H
3
4 /*
5 * urcu-static.h
6 *
7 * Userspace RCU header.
8 *
9 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking
10 * dynamically with the userspace rcu library.
11 *
12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
13 * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
14 *
15 * This library is free software; you can redistribute it and/or
16 * modify it under the terms of the GNU Lesser General Public
17 * License as published by the Free Software Foundation; either
18 * version 2.1 of the License, or (at your option) any later version.
19 *
20 * This library is distributed in the hope that it will be useful,
21 * but WITHOUT ANY WARRANTY; without even the implied warranty of
22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23 * Lesser General Public License for more details.
24 *
25 * You should have received a copy of the GNU Lesser General Public
26 * License along with this library; if not, write to the Free Software
27 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
28 *
29 * IBM's contributions to this file may be relicensed under LGPLv2 or later.
30 */
31
32 #include <stdlib.h>
33 #include <pthread.h>
34
35 #include <compiler.h>
36 #include <arch.h>
37
38
39 /*
40 * Number of entries in the per-thread reclaim queue. Must be power of 2.
41 */
42 #define RECLAIM_QUEUE_SIZE (1 << 12)
43 #define RECLAIM_QUEUE_MASK (RECLAIM_QUEUE_SIZE - 1)
44
45 /*
46 * Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
47 */
48 #define _LOAD_SHARED(p) ACCESS_ONCE(p)
49
50 /*
51 * Load a data from shared memory, doing a cache flush if required.
52 */
53 #define LOAD_SHARED(p) \
54 ({ \
55 smp_rmc(); \
56 _LOAD_SHARED(p); \
57 })
58
59 /*
60 * Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
61 */
62 #define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); })
63
64 /*
65 * Store v into x, where x is located in shared memory. Performs the required
66 * cache flush after writing. Returns v.
67 */
68 #define STORE_SHARED(x, v) \
69 ({ \
70 _STORE_SHARED(x, v); \
71 smp_wmc(); \
72 (v); \
73 })
74
75 /*
76 * This code section can only be included in LGPL 2.1 compatible source code.
77 * See below for the function call wrappers which can be used in code meant to
78 * be only linked with the Userspace RCU library. This comes with a small
79 * performance degradation on the read-side due to the added function calls.
80 * This is required to permit relinking with newer versions of the library.
81 */
82
83 #ifdef DEBUG_RCU
84 #define rcu_assert(args...) assert(args)
85 #else
86 #define rcu_assert(args...)
87 #endif
88
89 struct reclaim_queue {
90 unsigned long head; /* add element at head */
91 unsigned long tail; /* next element to remove at tail */
92 void **q;
93 };
94
95 extern struct reclaim_queue __thread reclaim_queue;
96
97 extern void rcu_reclaim_barrier_thread(void);
98
99 /*
100 * not signal-safe.
101 */
102 static inline void _rcu_reclaim_queue(void *p)
103 {
104 unsigned long head, tail;
105
106 /*
107 * Head is only modified by ourself. Tail can be modified by reclamation
108 * thread.
109 */
110 head = reclaim_queue.head;
111 tail = LOAD_SHARED(reclaim_queue.tail);
112
113 /*
114 * If queue is full, empty it ourself.
115 */
116 if (unlikely(head - tail >= RECLAIM_QUEUE_SIZE)) {
117 assert(head - tail == RECLAIM_QUEUE_SIZE);
118 rcu_reclaim_barrier_thread();
119 assert(head - LOAD_SHARED(reclaim_queue.tail) == 0);
120 }
121
122 smp_wmb(); /* Publish new pointer before write q[] */
123 _STORE_SHARED(reclaim_queue.q[head & RECLAIM_QUEUE_MASK], p);
124 smp_wmb(); /* Write q[] before head. */
125 STORE_SHARED(reclaim_queue.head, head + 1);
126 }
127
128 #endif /* _URCU_RECLAIM_STATIC_H */
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