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fdee2e6d MD |
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@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 | #include <syscall.h> | |
35 | #include <unistd.h> | |
36 | ||
37 | #include <urcu/compiler.h> | |
38 | #include <urcu/arch.h> | |
39 | #include <urcu/system.h> | |
48d848c7 | 40 | #include <urcu/uatomic_arch.h> |
fdee2e6d MD |
41 | #include <urcu/list.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 | ||
36bc70a8 MD |
51 | #ifdef __cplusplus |
52 | extern "C" { | |
53 | #endif | |
54 | ||
fdee2e6d MD |
55 | /* |
56 | * Active attempts to check for reader Q.S. before calling sleep(). | |
57 | */ | |
58 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
59 | ||
60 | #ifdef DEBUG_RCU | |
61 | #define rcu_assert(args...) assert(args) | |
62 | #else | |
63 | #define rcu_assert(args...) | |
64 | #endif | |
65 | ||
66 | #ifdef DEBUG_YIELD | |
67 | #include <sched.h> | |
68 | #include <time.h> | |
69 | #include <pthread.h> | |
70 | #include <unistd.h> | |
71 | ||
72 | #define YIELD_READ (1 << 0) | |
73 | #define YIELD_WRITE (1 << 1) | |
74 | ||
75 | /* | |
02be5561 | 76 | * Updates without RCU_MB are much slower. Account this in |
fdee2e6d MD |
77 | * the delay. |
78 | */ | |
79 | /* maximum sleep delay, in us */ | |
80 | #define MAX_SLEEP 50 | |
81 | ||
82 | extern unsigned int yield_active; | |
83 | extern unsigned int __thread rand_yield; | |
84 | ||
85 | static inline void debug_yield_read(void) | |
86 | { | |
87 | if (yield_active & YIELD_READ) | |
88 | if (rand_r(&rand_yield) & 0x1) | |
89 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
90 | } | |
91 | ||
92 | static inline void debug_yield_write(void) | |
93 | { | |
94 | if (yield_active & YIELD_WRITE) | |
95 | if (rand_r(&rand_yield) & 0x1) | |
96 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
97 | } | |
98 | ||
99 | static inline void debug_yield_init(void) | |
100 | { | |
101 | rand_yield = time(NULL) ^ pthread_self(); | |
102 | } | |
103 | #else | |
104 | static inline void debug_yield_read(void) | |
105 | { | |
106 | } | |
107 | ||
108 | static inline void debug_yield_write(void) | |
109 | { | |
110 | } | |
111 | ||
112 | static inline void debug_yield_init(void) | |
113 | { | |
114 | ||
115 | } | |
116 | #endif | |
117 | ||
118 | /* | |
02be5561 | 119 | * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use a |
fdee2e6d MD |
120 | * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits. |
121 | */ | |
122 | #define RCU_GP_COUNT (1UL << 0) | |
123 | /* Use the amount of bits equal to half of the architecture long size */ | |
02be5561 MD |
124 | #define RCU_GP_CTR_PHASE (1UL << (sizeof(long) << 2)) |
125 | #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1) | |
fdee2e6d MD |
126 | |
127 | /* | |
128 | * Used internally by _rcu_read_lock. | |
129 | */ | |
130 | extern void rcu_bp_register(void); | |
131 | ||
132 | /* | |
133 | * Global quiescent period counter with low-order bits unused. | |
134 | * Using a int rather than a char to eliminate false register dependencies | |
135 | * causing stalls on some architectures. | |
136 | */ | |
02be5561 | 137 | extern long rcu_gp_ctr; |
fdee2e6d | 138 | |
02be5561 | 139 | struct rcu_reader { |
fdee2e6d MD |
140 | /* Data used by both reader and synchronize_rcu() */ |
141 | long ctr; | |
142 | /* Data used for registry */ | |
143 | struct list_head head __attribute__((aligned(CACHE_LINE_SIZE))); | |
144 | pthread_t tid; | |
145 | int alloc; /* registry entry allocated */ | |
146 | }; | |
147 | ||
148 | /* | |
149 | * Bulletproof version keeps a pointer to a registry not part of the TLS. | |
150 | * Adds a pointer dereference on the read-side, but won't require to unregister | |
151 | * the reader thread. | |
152 | */ | |
02be5561 | 153 | extern struct rcu_reader __thread *rcu_reader; |
fdee2e6d MD |
154 | |
155 | static inline int rcu_old_gp_ongoing(long *value) | |
156 | { | |
157 | long v; | |
158 | ||
159 | if (value == NULL) | |
160 | return 0; | |
161 | /* | |
162 | * Make sure both tests below are done on the same version of *value | |
163 | * to insure consistency. | |
164 | */ | |
165 | v = LOAD_SHARED(*value); | |
166 | return (v & RCU_GP_CTR_NEST_MASK) && | |
02be5561 | 167 | ((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE); |
fdee2e6d MD |
168 | } |
169 | ||
170 | static inline void _rcu_read_lock(void) | |
171 | { | |
172 | long tmp; | |
173 | ||
174 | /* Check if registered */ | |
02be5561 | 175 | if (unlikely(!rcu_reader)) |
fdee2e6d MD |
176 | rcu_bp_register(); |
177 | ||
02be5561 MD |
178 | tmp = rcu_reader->ctr; |
179 | /* | |
180 | * rcu_gp_ctr is | |
181 | * RCU_GP_COUNT | (~RCU_GP_CTR_PHASE or RCU_GP_CTR_PHASE) | |
182 | */ | |
fdee2e6d | 183 | if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) { |
02be5561 | 184 | _STORE_SHARED(rcu_reader->ctr, _LOAD_SHARED(rcu_gp_ctr)); |
fdee2e6d MD |
185 | /* |
186 | * Set active readers count for outermost nesting level before | |
187 | * accessing the pointer. | |
188 | */ | |
189 | smp_mb(); | |
190 | } else { | |
02be5561 | 191 | _STORE_SHARED(rcu_reader->ctr, tmp + RCU_GP_COUNT); |
fdee2e6d MD |
192 | } |
193 | } | |
194 | ||
195 | static inline void _rcu_read_unlock(void) | |
196 | { | |
197 | /* | |
198 | * Finish using rcu before decrementing the pointer. | |
199 | */ | |
200 | smp_mb(); | |
02be5561 | 201 | _STORE_SHARED(rcu_reader->ctr, rcu_reader->ctr - RCU_GP_COUNT); |
fdee2e6d MD |
202 | } |
203 | ||
36bc70a8 MD |
204 | #ifdef __cplusplus |
205 | } | |
206 | #endif | |
207 | ||
fdee2e6d | 208 | #endif /* _URCU_BP_STATIC_H */ |