d30365a49f027ae09fc6c209d791a6196ce82d5b
[urcu.git] / include / urcu / static / urcu-memb.h
1 #ifndef _URCU_MEMB_STATIC_H
2 #define _URCU_MEMB_STATIC_H
3
4 /*
5 * urcu-memb-static.h
6 *
7 * Userspace RCU header.
8 *
9 * TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU
10 * RELEASE. See urcu.h for linking dynamically with the userspace rcu library.
11 *
12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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 #include <unistd.h>
35 #include <stdint.h>
36
37 #include <urcu/config.h>
38 #include <urcu/compiler.h>
39 #include <urcu/arch.h>
40 #include <urcu/system.h>
41 #include <urcu/uatomic.h>
42 #include <urcu/list.h>
43 #include <urcu/futex.h>
44 #include <urcu/tls-compat.h>
45 #include <urcu/debug.h>
46 #include <urcu/static/urcu-common.h>
47
48 #ifdef __cplusplus
49 extern "C" {
50 #endif
51
52 /*
53 * This code section can only be included in LGPL 2.1 compatible source code.
54 * See below for the function call wrappers which can be used in code meant to
55 * be only linked with the Userspace RCU library. This comes with a small
56 * performance degradation on the read-side due to the added function calls.
57 * This is required to permit relinking with newer versions of the library.
58 */
59
60 /*
61 * Slave barriers are only guaranteed to be ordered wrt master barriers.
62 *
63 * The pair ordering is detailed as (O: ordered, X: not ordered) :
64 * slave master
65 * slave X O
66 * master O O
67 */
68
69 #ifdef CONFIG_RCU_FORCE_SYS_MEMBARRIER
70 #define urcu_memb_has_sys_membarrier 1
71 #else
72 extern int urcu_memb_has_sys_membarrier;
73 #endif
74
75 static inline void urcu_memb_smp_mb_slave(void)
76 {
77 if (caa_likely(urcu_memb_has_sys_membarrier))
78 cmm_barrier();
79 else
80 cmm_smp_mb();
81 }
82
83 extern struct urcu_gp urcu_memb_gp;
84
85 extern DECLARE_URCU_TLS(struct urcu_reader, urcu_memb_reader);
86
87 /*
88 * Helper for _rcu_read_lock(). The format of urcu_memb_gp.ctr (as well as
89 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
90 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
91 * or URCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
92 * _rcu_read_lock() happen before the subsequent read-side critical section.
93 */
94 static inline void _urcu_memb_read_lock_update(unsigned long tmp)
95 {
96 if (caa_likely(!(tmp & URCU_GP_CTR_NEST_MASK))) {
97 _CMM_STORE_SHARED(URCU_TLS(urcu_memb_reader).ctr, _CMM_LOAD_SHARED(urcu_memb_gp.ctr));
98 urcu_memb_smp_mb_slave();
99 } else
100 _CMM_STORE_SHARED(URCU_TLS(urcu_memb_reader).ctr, tmp + URCU_GP_COUNT);
101 }
102
103 /*
104 * Enter an RCU read-side critical section.
105 *
106 * The first cmm_barrier() call ensures that the compiler does not reorder
107 * the body of _rcu_read_lock() with a mutex.
108 *
109 * This function and its helper are both less than 10 lines long. The
110 * intent is that this function meets the 10-line criterion in LGPL,
111 * allowing this function to be invoked directly from non-LGPL code.
112 */
113 static inline void _urcu_memb_read_lock(void)
114 {
115 unsigned long tmp;
116
117 urcu_assert(URCU_TLS(urcu_memb_reader).registered);
118 cmm_barrier();
119 tmp = URCU_TLS(urcu_memb_reader).ctr;
120 urcu_assert((tmp & URCU_GP_CTR_NEST_MASK) != URCU_GP_CTR_NEST_MASK);
121 _urcu_memb_read_lock_update(tmp);
122 }
123
124 /*
125 * This is a helper function for _rcu_read_unlock().
126 *
127 * The first smp_mb_slave() call ensures that the critical section is
128 * seen to precede the store to rcu_reader.ctr.
129 * The second smp_mb_slave() call ensures that we write to rcu_reader.ctr
130 * before reading the update-side futex.
131 */
132 static inline void _urcu_memb_read_unlock_update_and_wakeup(unsigned long tmp)
133 {
134 if (caa_likely((tmp & URCU_GP_CTR_NEST_MASK) == URCU_GP_COUNT)) {
135 urcu_memb_smp_mb_slave();
136 _CMM_STORE_SHARED(URCU_TLS(urcu_memb_reader).ctr, tmp - URCU_GP_COUNT);
137 urcu_memb_smp_mb_slave();
138 urcu_common_wake_up_gp(&urcu_memb_gp);
139 } else
140 _CMM_STORE_SHARED(URCU_TLS(urcu_memb_reader).ctr, tmp - URCU_GP_COUNT);
141 }
142
143 /*
144 * Exit an RCU read-side critical section. Both this function and its
145 * helper are smaller than 10 lines of code, and are intended to be
146 * usable by non-LGPL code, as called out in LGPL.
147 */
148 static inline void _urcu_memb_read_unlock(void)
149 {
150 unsigned long tmp;
151
152 urcu_assert(URCU_TLS(urcu_memb_reader).registered);
153 tmp = URCU_TLS(urcu_memb_reader).ctr;
154 urcu_assert(tmp & URCU_GP_CTR_NEST_MASK);
155 _urcu_memb_read_unlock_update_and_wakeup(tmp);
156 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
157 }
158
159 /*
160 * Returns whether within a RCU read-side critical section.
161 *
162 * This function is less than 10 lines long. The intent is that this
163 * function meets the 10-line criterion for LGPL, allowing this function
164 * to be invoked directly from non-LGPL code.
165 */
166 static inline int _urcu_memb_read_ongoing(void)
167 {
168 return URCU_TLS(urcu_memb_reader).ctr & URCU_GP_CTR_NEST_MASK;
169 }
170
171 #ifdef __cplusplus
172 }
173 #endif
174
175 #endif /* _URCU_MEMB_STATIC_H */
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