Restrict supported arch ot P6+ on Intel x86 32.
[urcu.git] / urcu-qsbr-static.h
1 #ifndef _URCU_QSBR_STATIC_H
2 #define _URCU_QSBR_STATIC_H
3
4 /*
5 * urcu-qsbr-static.h
6 *
7 * Userspace RCU QSBR header.
8 *
9 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-qsbr.h for linking
10 * dynamically with the userspace rcu QSBR 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 <assert.h>
35 #include <limits.h>
36 #include <syscall.h>
37 #include <unistd.h>
38
39 #include <urcu/compiler.h>
40 #include <urcu/arch.h>
41 #include <urcu/system.h>
42 #include <urcu/uatomic_arch.h>
43 #include <urcu/list.h>
44
45 #define futex(...) syscall(__NR_futex, __VA_ARGS__)
46 #define FUTEX_WAIT 0
47 #define FUTEX_WAKE 1
48
49 /*
50 * This code section can only be included in LGPL 2.1 compatible source code.
51 * See below for the function call wrappers which can be used in code meant to
52 * be only linked with the Userspace RCU library. This comes with a small
53 * performance degradation on the read-side due to the added function calls.
54 * This is required to permit relinking with newer versions of the library.
55 */
56
57 /*
58 * If a reader is really non-cooperative and refuses to commit its
59 * urcu_reader.ctr count to memory (there is no barrier in the reader
60 * per-se), kick it after a few loops waiting for it.
61 */
62 #define KICK_READER_LOOPS 10000
63
64 /*
65 * Active attempts to check for reader Q.S. before calling futex().
66 */
67 #define RCU_QS_ACTIVE_ATTEMPTS 100
68
69 #ifdef DEBUG_RCU
70 #define rcu_assert(args...) assert(args)
71 #else
72 #define rcu_assert(args...)
73 #endif
74
75 #ifdef DEBUG_YIELD
76 #include <sched.h>
77 #include <time.h>
78 #include <pthread.h>
79 #include <unistd.h>
80
81 #define YIELD_READ (1 << 0)
82 #define YIELD_WRITE (1 << 1)
83
84 /* maximum sleep delay, in us */
85 #define MAX_SLEEP 50
86
87 extern unsigned int yield_active;
88 extern unsigned int __thread rand_yield;
89
90 static inline void debug_yield_read(void)
91 {
92 if (yield_active & YIELD_READ)
93 if (rand_r(&rand_yield) & 0x1)
94 usleep(rand_r(&rand_yield) % MAX_SLEEP);
95 }
96
97 static inline void debug_yield_write(void)
98 {
99 if (yield_active & YIELD_WRITE)
100 if (rand_r(&rand_yield) & 0x1)
101 usleep(rand_r(&rand_yield) % MAX_SLEEP);
102 }
103
104 static inline void debug_yield_init(void)
105 {
106 rand_yield = time(NULL) ^ pthread_self();
107 }
108 #else
109 static inline void debug_yield_read(void)
110 {
111 }
112
113 static inline void debug_yield_write(void)
114 {
115 }
116
117 static inline void debug_yield_init(void)
118 {
119
120 }
121 #endif
122
123 static inline void reader_barrier()
124 {
125 smp_mb();
126 }
127
128 #define RCU_GP_ONLINE (1UL << 0)
129 #define RCU_GP_CTR (1UL << 1)
130
131 /*
132 * Global quiescent period counter with low-order bits unused.
133 * Using a int rather than a char to eliminate false register dependencies
134 * causing stalls on some architectures.
135 */
136 extern unsigned long urcu_gp_ctr;
137
138 struct urcu_reader {
139 /* Data used by both reader and synchronize_rcu() */
140 unsigned long ctr;
141 /* Data used for registry */
142 struct list_head head __attribute__((aligned(CACHE_LINE_SIZE)));
143 pthread_t tid;
144 };
145
146 extern struct urcu_reader __thread urcu_reader;
147
148 extern int gp_futex;
149
150 /*
151 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
152 */
153 static inline void wake_up_gp(void)
154 {
155 if (unlikely(uatomic_read(&gp_futex) == -1)) {
156 uatomic_set(&gp_futex, 0);
157 futex(&gp_futex, FUTEX_WAKE, 1,
158 NULL, NULL, 0);
159 }
160 }
161
162 #if (BITS_PER_LONG < 64)
163 static inline int rcu_gp_ongoing(unsigned long *value)
164 {
165 unsigned long reader_gp;
166
167 if (value == NULL)
168 return 0;
169 reader_gp = LOAD_SHARED(*value);
170 return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR);
171 }
172 #else /* !(BITS_PER_LONG < 64) */
173 static inline int rcu_gp_ongoing(unsigned long *value)
174 {
175 unsigned long reader_gp;
176
177 if (value == NULL)
178 return 0;
179 reader_gp = LOAD_SHARED(*value);
180 return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2);
181 }
182 #endif /* !(BITS_PER_LONG < 64) */
183
184 static inline void _rcu_read_lock(void)
185 {
186 rcu_assert(urcu_reader.ctr);
187 }
188
189 static inline void _rcu_read_unlock(void)
190 {
191 }
192
193 static inline void _rcu_quiescent_state(void)
194 {
195 smp_mb();
196 _STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr));
197 smp_mb(); /* write urcu_reader.ctr before read futex */
198 wake_up_gp();
199 smp_mb();
200 }
201
202 static inline void _rcu_thread_offline(void)
203 {
204 smp_mb();
205 STORE_SHARED(urcu_reader.ctr, 0);
206 smp_mb(); /* write urcu_reader.ctr before read futex */
207 wake_up_gp();
208 }
209
210 static inline void _rcu_thread_online(void)
211 {
212 _STORE_SHARED(urcu_reader.ctr, LOAD_SHARED(urcu_gp_ctr));
213 smp_mb();
214 }
215
216 #endif /* _URCU_QSBR_STATIC_H */
This page took 0.0487 seconds and 4 git commands to generate.