Add extern "C" to support linking userspace RCU library with C++ applications
[urcu.git] / urcu-defer-static.h
1 #ifndef _URCU_DEFER_STATIC_H
2 #define _URCU_DEFER_STATIC_H
3
4 /*
5 * urcu-defer-static.h
6 *
7 * Userspace RCU header - memory reclamation.
8 *
9 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-defer.h for linking
10 * dynamically with the userspace rcu reclamation 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 <urcu/compiler.h>
36 #include <urcu/arch.h>
37 #include <urcu/uatomic_arch.h>
38 #include <urcu/list.h>
39
40 #ifdef __cplusplus
41 extern "C" {
42 #endif
43
44 /*
45 * Number of entries in the per-thread defer queue. Must be power of 2.
46 */
47 #define DEFER_QUEUE_SIZE (1 << 12)
48 #define DEFER_QUEUE_MASK (DEFER_QUEUE_SIZE - 1)
49
50 /*
51 * Typically, data is aligned at least on the architecture size.
52 * Use lowest bit to indicate that the current callback is changing.
53 * Assumes that (void *)-2L is not used often. Used to encode non-aligned
54 * functions and non-aligned data using extra space.
55 * We encode the (void *)-2L fct as: -2L, fct, data.
56 * We encode the (void *)-2L data as: -2L, fct, data.
57 * Here, DQ_FCT_MARK == ~DQ_FCT_BIT. Required for the test order.
58 */
59 #define DQ_FCT_BIT (1 << 0)
60 #define DQ_IS_FCT_BIT(x) ((unsigned long)(x) & DQ_FCT_BIT)
61 #define DQ_SET_FCT_BIT(x) \
62 (x = (void *)((unsigned long)(x) | DQ_FCT_BIT))
63 #define DQ_CLEAR_FCT_BIT(x) \
64 (x = (void *)((unsigned long)(x) & ~DQ_FCT_BIT))
65 #define DQ_FCT_MARK ((void *)(~DQ_FCT_BIT))
66
67 /*
68 * Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
69 */
70 #define _LOAD_SHARED(p) ACCESS_ONCE(p)
71
72 /*
73 * Load a data from shared memory, doing a cache flush if required.
74 */
75 #define LOAD_SHARED(p) \
76 ({ \
77 smp_rmc(); \
78 _LOAD_SHARED(p); \
79 })
80
81 /*
82 * Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
83 */
84 #define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); })
85
86 /*
87 * Store v into x, where x is located in shared memory. Performs the required
88 * cache flush after writing. Returns v.
89 */
90 #define STORE_SHARED(x, v) \
91 ({ \
92 _STORE_SHARED(x, v); \
93 smp_wmc(); \
94 (v); \
95 })
96
97 /*
98 * This code section can only be included in LGPL 2.1 compatible source code.
99 * See below for the function call wrappers which can be used in code meant to
100 * be only linked with the Userspace RCU library. This comes with a small
101 * performance degradation on the read-side due to the added function calls.
102 * This is required to permit relinking with newer versions of the library.
103 */
104
105 #ifdef DEBUG_RCU
106 #define rcu_assert(args...) assert(args)
107 #else
108 #define rcu_assert(args...)
109 #endif
110
111 /*
112 * defer queue.
113 * Contains pointers. Encoded to save space when same callback is often used.
114 * When looking up the next item:
115 * - if DQ_FCT_BIT is set, set the current callback to DQ_CLEAR_FCT_BIT(ptr)
116 * - next element contains pointer to data.
117 * - else if item == DQ_FCT_MARK
118 * - set the current callback to next element ptr
119 * - following next element contains pointer to data.
120 * - else current element contains data
121 */
122 struct defer_queue {
123 unsigned long head; /* add element at head */
124 void *last_fct_in; /* last fct pointer encoded */
125 unsigned long tail; /* next element to remove at tail */
126 void *last_fct_out; /* last fct pointer encoded */
127 void **q;
128 /* registry information */
129 unsigned long last_head;
130 struct list_head list; /* list of thread queues */
131 };
132
133 #ifdef __cplusplus
134 }
135 #endif
136
137 #endif /* _URCU_DEFER_STATIC_H */
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