uatomic compat: complete i386 support
[urcu.git] / urcu-static.h
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1#ifndef _URCU_STATIC_H
2#define _URCU_STATIC_H
3
4/*
5 * urcu-static.h
6 *
d2d23035 7 * Userspace RCU header.
adcfce54 8 *
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9 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking
10 * dynamically with the userspace rcu library.
adcfce54 11 *
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12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
13 * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
adcfce54 14 *
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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
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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>
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34#include <syscall.h>
35#include <unistd.h>
adcfce54 36
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37#include <urcu/compiler.h>
38#include <urcu/arch.h>
7e30abe3 39#include <urcu/system.h>
48d848c7 40#include <urcu/uatomic_arch.h>
e3b0cef0 41#include <urcu/list.h>
0854ccff 42#include <urcu/urcu-futex.h>
bc6c15bb 43
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44/*
45 * This code section can only be included in LGPL 2.1 compatible source code.
46 * See below for the function call wrappers which can be used in code meant to
47 * be only linked with the Userspace RCU library. This comes with a small
48 * performance degradation on the read-side due to the added function calls.
49 * This is required to permit relinking with newer versions of the library.
50 */
51
52/*
53 * The signal number used by the RCU library can be overridden with
54 * -DSIGURCU= when compiling the library.
55 */
56#ifndef SIGURCU
57#define SIGURCU SIGUSR1
58#endif
59
60/*
61 * If a reader is really non-cooperative and refuses to commit its
62 * urcu_active_readers count to memory (there is no barrier in the reader
63 * per-se), kick it after a few loops waiting for it.
64 */
65#define KICK_READER_LOOPS 10000
66
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67/*
68 * Active attempts to check for reader Q.S. before calling futex().
69 */
70#define RCU_QS_ACTIVE_ATTEMPTS 100
71
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72#ifdef DEBUG_RCU
73#define rcu_assert(args...) assert(args)
74#else
75#define rcu_assert(args...)
76#endif
77
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78#ifdef DEBUG_YIELD
79#include <sched.h>
80#include <time.h>
81#include <pthread.h>
82#include <unistd.h>
83
84#define YIELD_READ (1 << 0)
85#define YIELD_WRITE (1 << 1)
86
b4ce1526 87/*
0a1d290b 88 * Updates without URCU_MB are much slower. Account this in
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89 * the delay.
90 */
0a1d290b 91#ifdef URCU_MB
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92/* maximum sleep delay, in us */
93#define MAX_SLEEP 50
94#else
95#define MAX_SLEEP 30000
96#endif
97
98extern unsigned int yield_active;
99extern unsigned int __thread rand_yield;
100
101static inline void debug_yield_read(void)
102{
103 if (yield_active & YIELD_READ)
104 if (rand_r(&rand_yield) & 0x1)
105 usleep(rand_r(&rand_yield) % MAX_SLEEP);
106}
107
108static inline void debug_yield_write(void)
109{
110 if (yield_active & YIELD_WRITE)
111 if (rand_r(&rand_yield) & 0x1)
112 usleep(rand_r(&rand_yield) % MAX_SLEEP);
113}
114
115static inline void debug_yield_init(void)
116{
117 rand_yield = time(NULL) ^ pthread_self();
118}
119#else
120static inline void debug_yield_read(void)
121{
122}
123
124static inline void debug_yield_write(void)
125{
126}
127
128static inline void debug_yield_init(void)
129{
130
131}
132#endif
133
0a1d290b 134#ifdef URCU_MB
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135static inline void reader_barrier()
136{
137 smp_mb();
138}
139#else
140static inline void reader_barrier()
141{
142 barrier();
143}
144#endif
145
146/*
147 * The trick here is that RCU_GP_CTR_BIT must be a multiple of 8 so we can use a
148 * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
149 */
150#define RCU_GP_COUNT (1UL << 0)
151/* Use the amount of bits equal to half of the architecture long size */
152#define RCU_GP_CTR_BIT (1UL << (sizeof(long) << 2))
153#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_BIT - 1)
154
155/*
156 * Global quiescent period counter with low-order bits unused.
157 * Using a int rather than a char to eliminate false register dependencies
158 * causing stalls on some architectures.
159 */
160extern long urcu_gp_ctr;
161
e3b0cef0 162struct urcu_reader {
bd1a5e15 163 /* Data used by both reader and synchronize_rcu() */
e3b0cef0 164 long ctr;
e3b0cef0 165 char need_mb;
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166 /* Data used for registry */
167 struct list_head head __attribute__((aligned(CACHE_LINE_SIZE)));
168 pthread_t tid;
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169};
170
171extern struct urcu_reader __thread urcu_reader;
adcfce54 172
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173extern int gp_futex;
174
175/*
176 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
177 */
178static inline void wake_up_gp(void)
179{
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180 if (unlikely(uatomic_read(&gp_futex) == -1)) {
181 uatomic_set(&gp_futex, 0);
0854ccff 182 futex_async(&gp_futex, FUTEX_WAKE, 1,
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183 NULL, NULL, 0);
184 }
185}
186
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187static inline int rcu_old_gp_ongoing(long *value)
188{
189 long v;
190
191 if (value == NULL)
192 return 0;
193 /*
194 * Make sure both tests below are done on the same version of *value
195 * to insure consistency.
196 */
197 v = LOAD_SHARED(*value);
198 return (v & RCU_GP_CTR_NEST_MASK) &&
199 ((v ^ urcu_gp_ctr) & RCU_GP_CTR_BIT);
200}
201
202static inline void _rcu_read_lock(void)
203{
204 long tmp;
205
e3b0cef0 206 tmp = urcu_reader.ctr;
adcfce54 207 /* urcu_gp_ctr = RCU_GP_COUNT | (~RCU_GP_CTR_BIT or RCU_GP_CTR_BIT) */
67ef1a2c 208 if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
e3b0cef0 209 _STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr));
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210 /*
211 * Set active readers count for outermost nesting level before
212 * accessing the pointer. See force_mb_all_threads().
213 */
214 reader_barrier();
215 } else {
e3b0cef0 216 _STORE_SHARED(urcu_reader.ctr, tmp + RCU_GP_COUNT);
67ef1a2c 217 }
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218}
219
220static inline void _rcu_read_unlock(void)
221{
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222 long tmp;
223
e3b0cef0 224 tmp = urcu_reader.ctr;
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225 /*
226 * Finish using rcu before decrementing the pointer.
227 * See force_mb_all_threads().
228 */
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229 if (likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
230 reader_barrier();
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231 _STORE_SHARED(urcu_reader.ctr, urcu_reader.ctr - RCU_GP_COUNT);
232 /* write urcu_reader.ctr before read futex */
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233 reader_barrier();
234 wake_up_gp();
235 } else {
e3b0cef0 236 _STORE_SHARED(urcu_reader.ctr, urcu_reader.ctr - RCU_GP_COUNT);
bc6c15bb 237 }
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238}
239
adcfce54 240#endif /* _URCU_STATIC_H */
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