Use urcu/tls-compat.h
[userspace-rcu.git] / urcu / static / urcu-bp.h
1 #ifndef _URCU_BP_STATIC_H
2 #define _URCU_BP_STATIC_H
3
4 /*
5 * urcu-bp-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@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
36 #include <urcu/compiler.h>
37 #include <urcu/arch.h>
38 #include <urcu/system.h>
39 #include <urcu/uatomic.h>
40 #include <urcu/list.h>
41 #include <urcu/tls-compat.h>
42
43 /*
44 * This code section can only be included in LGPL 2.1 compatible source code.
45 * See below for the function call wrappers which can be used in code meant to
46 * be only linked with the Userspace RCU library. This comes with a small
47 * performance degradation on the read-side due to the added function calls.
48 * This is required to permit relinking with newer versions of the library.
49 */
50
51 #ifdef __cplusplus
52 extern "C" {
53 #endif
54
55 #ifdef DEBUG_RCU
56 #define rcu_assert(args...) assert(args)
57 #else
58 #define rcu_assert(args...)
59 #endif
60
61 #ifdef DEBUG_YIELD
62 #include <sched.h>
63 #include <time.h>
64 #include <pthread.h>
65 #include <unistd.h>
66
67 #define YIELD_READ (1 << 0)
68 #define YIELD_WRITE (1 << 1)
69
70 /*
71 * Updates without RCU_MB are much slower. Account this in
72 * the delay.
73 */
74 /* maximum sleep delay, in us */
75 #define MAX_SLEEP 50
76
77 extern unsigned int yield_active;
78 extern DECLARE_URCU_TLS(unsigned int, rand_yield);
79
80 static inline void debug_yield_read(void)
81 {
82 if (yield_active & YIELD_READ)
83 if (rand_r(&URCU_TLS(rand_yield)) & 0x1)
84 usleep(rand_r(&URCU_TLS(rand_yield)) % MAX_SLEEP);
85 }
86
87 static inline void debug_yield_write(void)
88 {
89 if (yield_active & YIELD_WRITE)
90 if (rand_r(&URCU_TLS(rand_yield)) & 0x1)
91 usleep(rand_r(&URCU_TLS(rand_yield)) % MAX_SLEEP);
92 }
93
94 static inline void debug_yield_init(void)
95 {
96 URCU_TLS(rand_yield) = time(NULL) ^ pthread_self();
97 }
98 #else
99 static inline void debug_yield_read(void)
100 {
101 }
102
103 static inline void debug_yield_write(void)
104 {
105 }
106
107 static inline void debug_yield_init(void)
108 {
109
110 }
111 #endif
112
113 /*
114 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use a
115 * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
116 */
117 #define RCU_GP_COUNT (1UL << 0)
118 /* Use the amount of bits equal to half of the architecture long size */
119 #define RCU_GP_CTR_PHASE (1UL << (sizeof(long) << 2))
120 #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
121
122 /*
123 * Used internally by _rcu_read_lock.
124 */
125 extern void rcu_bp_register(void);
126
127 /*
128 * Global quiescent period counter with low-order bits unused.
129 * Using a int rather than a char to eliminate false register dependencies
130 * causing stalls on some architectures.
131 */
132 extern long rcu_gp_ctr;
133
134 struct rcu_reader {
135 /* Data used by both reader and synchronize_rcu() */
136 long ctr;
137 /* Data used for registry */
138 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
139 pthread_t tid;
140 int alloc; /* registry entry allocated */
141 };
142
143 /*
144 * Bulletproof version keeps a pointer to a registry not part of the TLS.
145 * Adds a pointer dereference on the read-side, but won't require to unregister
146 * the reader thread.
147 */
148 extern DECLARE_URCU_TLS(struct rcu_reader *, rcu_reader);
149
150 static inline int rcu_old_gp_ongoing(long *value)
151 {
152 long v;
153
154 if (value == NULL)
155 return 0;
156 /*
157 * Make sure both tests below are done on the same version of *value
158 * to insure consistency.
159 */
160 v = CMM_LOAD_SHARED(*value);
161 return (v & RCU_GP_CTR_NEST_MASK) &&
162 ((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE);
163 }
164
165 static inline void _rcu_read_lock(void)
166 {
167 long tmp;
168
169 /* Check if registered */
170 if (caa_unlikely(!URCU_TLS(rcu_reader)))
171 rcu_bp_register();
172
173 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
174 tmp = URCU_TLS(rcu_reader)->ctr;
175 /*
176 * rcu_gp_ctr is
177 * RCU_GP_COUNT | (~RCU_GP_CTR_PHASE or RCU_GP_CTR_PHASE)
178 */
179 if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
180 _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
181 /*
182 * Set active readers count for outermost nesting level before
183 * accessing the pointer.
184 */
185 cmm_smp_mb();
186 } else {
187 _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, tmp + RCU_GP_COUNT);
188 }
189 }
190
191 static inline void _rcu_read_unlock(void)
192 {
193 /*
194 * Finish using rcu before decrementing the pointer.
195 */
196 cmm_smp_mb();
197 _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, URCU_TLS(rcu_reader)->ctr - RCU_GP_COUNT);
198 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
199 }
200
201 #ifdef __cplusplus
202 }
203 #endif
204
205 #endif /* _URCU_BP_STATIC_H */
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