tls-compat.h: document sigaltstack(2) limitation
[urcu.git] / urcu / static / urcu.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 *
6982d6d7 12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
d2d23035 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>
bc6c15bb 34#include <unistd.h>
6d841bc2 35#include <stdint.h>
adcfce54 36
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37#include <urcu/compiler.h>
38#include <urcu/arch.h>
7e30abe3 39#include <urcu/system.h>
a2e7bf9c 40#include <urcu/uatomic.h>
e3b0cef0 41#include <urcu/list.h>
41849996 42#include <urcu/futex.h>
bd252a04 43#include <urcu/tls-compat.h>
bc6c15bb 44
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45#ifdef __cplusplus
46extern "C" {
47#endif
48
65f1e634 49/* Default is RCU_MEMBARRIER */
fdf01eed 50#if !defined(RCU_MEMBARRIER) && !defined(RCU_MB) && !defined(RCU_SIGNAL)
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51#define RCU_MEMBARRIER
52#endif
53
54/*
55 * RCU_MEMBARRIER is only possibly available on Linux. Fallback to RCU_MB
56 * otherwise.
57 */
58#if !defined(__linux__) && defined(RCU_MEMBARRIER)
59#undef RCU_MEMBARRIER
60#define RCU_MB
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61#endif
62
63#ifdef RCU_MEMBARRIER
4906d398 64#include <syscall.h>
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65
66/* If the headers do not support SYS_membarrier, statically use RCU_MB */
67#ifdef SYS_membarrier
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68# define MEMBARRIER_EXPEDITED (1 << 0)
69# define MEMBARRIER_DELAYED (1 << 1)
70# define MEMBARRIER_QUERY (1 << 16)
d4fc680a 71# define membarrier(...) syscall(SYS_membarrier, __VA_ARGS__)
fdf01eed 72#else
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73# undef RCU_MEMBARRIER
74# define RCU_MB
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75#endif
76#endif
77
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78/*
79 * This code section can only be included in LGPL 2.1 compatible source code.
80 * See below for the function call wrappers which can be used in code meant to
81 * be only linked with the Userspace RCU library. This comes with a small
82 * performance degradation on the read-side due to the added function calls.
83 * This is required to permit relinking with newer versions of the library.
84 */
85
86/*
87 * The signal number used by the RCU library can be overridden with
02be5561 88 * -DSIGRCU= when compiling the library.
ddf7eefb 89 * Provide backward compatibility for liburcu 0.3.x SIGURCU.
adcfce54 90 */
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91#ifdef SIGURCU
92#define SIGRCU SIGURCU
93#endif
94
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95#ifndef SIGRCU
96#define SIGRCU SIGUSR1
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97#endif
98
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99#ifdef DEBUG_RCU
100#define rcu_assert(args...) assert(args)
101#else
102#define rcu_assert(args...)
103#endif
104
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105#ifdef DEBUG_YIELD
106#include <sched.h>
107#include <time.h>
108#include <pthread.h>
109#include <unistd.h>
110
111#define YIELD_READ (1 << 0)
112#define YIELD_WRITE (1 << 1)
113
b4ce1526 114/*
fdf01eed 115 * Updates with RCU_SIGNAL are much slower. Account this in the delay.
b4ce1526 116 */
fdf01eed 117#ifdef RCU_SIGNAL
adcfce54 118/* maximum sleep delay, in us */
adcfce54 119#define MAX_SLEEP 30000
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120#else
121#define MAX_SLEEP 50
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122#endif
123
124extern unsigned int yield_active;
bd252a04 125extern DECLARE_URCU_TLS(unsigned int, rand_yield);
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126
127static inline void debug_yield_read(void)
128{
129 if (yield_active & YIELD_READ)
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130 if (rand_r(&URCU_TLS(rand_yield)) & 0x1)
131 usleep(rand_r(&URCU_TLS(rand_yield)) % MAX_SLEEP);
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132}
133
134static inline void debug_yield_write(void)
135{
136 if (yield_active & YIELD_WRITE)
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137 if (rand_r(&URCU_TLS(rand_yield)) & 0x1)
138 usleep(rand_r(&URCU_TLS(rand_yield)) % MAX_SLEEP);
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139}
140
141static inline void debug_yield_init(void)
142{
bd252a04 143 URCU_TLS(rand_yield) = time(NULL) ^ (unsigned long) pthread_self();
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144}
145#else
146static inline void debug_yield_read(void)
147{
148}
149
150static inline void debug_yield_write(void)
151{
152}
153
154static inline void debug_yield_init(void)
155{
156
157}
158#endif
159
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160/*
161 * RCU memory barrier broadcast group. Currently, only broadcast to all process
162 * threads is supported (group 0).
163 *
164 * Slave barriers are only guaranteed to be ordered wrt master barriers.
165 *
166 * The pair ordering is detailed as (O: ordered, X: not ordered) :
167 * slave master
168 * slave X O
169 * master O O
170 */
171
172#define MB_GROUP_ALL 0
173#define RCU_MB_GROUP MB_GROUP_ALL
174
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175#ifdef RCU_MEMBARRIER
176extern int has_sys_membarrier;
177
25cc6d18 178static inline void smp_mb_slave(int group)
fdf01eed 179{
a0b7f7ea 180 if (caa_likely(has_sys_membarrier))
5481ddb3 181 cmm_barrier();
fdf01eed 182 else
5481ddb3 183 cmm_smp_mb();
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184}
185#endif
186
02be5561 187#ifdef RCU_MB
25cc6d18 188static inline void smp_mb_slave(int group)
adcfce54 189{
5481ddb3 190 cmm_smp_mb();
adcfce54 191}
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192#endif
193
194#ifdef RCU_SIGNAL
25cc6d18 195static inline void smp_mb_slave(int group)
adcfce54 196{
5481ddb3 197 cmm_barrier();
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198}
199#endif
200
201/*
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202 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use
203 * a full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
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204 */
205#define RCU_GP_COUNT (1UL << 0)
206/* Use the amount of bits equal to half of the architecture long size */
27d65bc5 207#define RCU_GP_CTR_PHASE (1UL << (sizeof(unsigned long) << 2))
02be5561 208#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
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209
210/*
211 * Global quiescent period counter with low-order bits unused.
212 * Using a int rather than a char to eliminate false register dependencies
213 * causing stalls on some architectures.
214 */
27d65bc5 215extern unsigned long rcu_gp_ctr;
adcfce54 216
02be5561 217struct rcu_reader {
bd1a5e15 218 /* Data used by both reader and synchronize_rcu() */
27d65bc5 219 unsigned long ctr;
e3b0cef0 220 char need_mb;
bd1a5e15 221 /* Data used for registry */
16aa9ee8 222 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
bd1a5e15 223 pthread_t tid;
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224};
225
bd252a04 226extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
adcfce54 227
6d841bc2 228extern int32_t gp_futex;
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229
230/*
231 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
232 */
233static inline void wake_up_gp(void)
234{
a0b7f7ea 235 if (caa_unlikely(uatomic_read(&gp_futex) == -1)) {
ec4e58a3 236 uatomic_set(&gp_futex, 0);
0854ccff 237 futex_async(&gp_futex, FUTEX_WAKE, 1,
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238 NULL, NULL, 0);
239 }
240}
241
e26fa029 242static inline int rcu_gp_ongoing(unsigned long *ctr)
adcfce54 243{
27d65bc5 244 unsigned long v;
adcfce54 245
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246 /*
247 * Make sure both tests below are done on the same version of *value
248 * to insure consistency.
249 */
6cf3827c 250 v = CMM_LOAD_SHARED(*ctr);
adcfce54 251 return (v & RCU_GP_CTR_NEST_MASK) &&
02be5561 252 ((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE);
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253}
254
255static inline void _rcu_read_lock(void)
256{
27d65bc5 257 unsigned long tmp;
adcfce54 258
5481ddb3 259 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
bd252a04 260 tmp = URCU_TLS(rcu_reader).ctr;
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261 /*
262 * rcu_gp_ctr is
263 * RCU_GP_COUNT | (~RCU_GP_CTR_PHASE or RCU_GP_CTR_PHASE)
264 */
a0b7f7ea 265 if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
bd252a04 266 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
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267 /*
268 * Set active readers count for outermost nesting level before
25cc6d18 269 * accessing the pointer. See smp_mb_master().
67ef1a2c 270 */
25cc6d18 271 smp_mb_slave(RCU_MB_GROUP);
67ef1a2c 272 } else {
bd252a04 273 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp + RCU_GP_COUNT);
67ef1a2c 274 }
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275}
276
277static inline void _rcu_read_unlock(void)
278{
27d65bc5 279 unsigned long tmp;
bc6c15bb 280
bd252a04 281 tmp = URCU_TLS(rcu_reader).ctr;
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282 /*
283 * Finish using rcu before decrementing the pointer.
25cc6d18 284 * See smp_mb_master().
adcfce54 285 */
a0b7f7ea 286 if (caa_likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
25cc6d18 287 smp_mb_slave(RCU_MB_GROUP);
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288 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, URCU_TLS(rcu_reader).ctr - RCU_GP_COUNT);
289 /* write URCU_TLS(rcu_reader).ctr before read futex */
25cc6d18 290 smp_mb_slave(RCU_MB_GROUP);
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291 wake_up_gp();
292 } else {
bd252a04 293 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, URCU_TLS(rcu_reader).ctr - RCU_GP_COUNT);
bc6c15bb 294 }
5481ddb3 295 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
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296}
297
ad918eeb 298#ifdef __cplusplus
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299}
300#endif
301
adcfce54 302#endif /* _URCU_STATIC_H */
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