Enhance test cases
[urcu.git] / urcu.c
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1/*
2 * urcu.c
3 *
4 * Userspace RCU library
5 *
6 * Copyright February 2009 - Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
7 *
8 * Distributed under GPLv2
9 */
10
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11#include <stdio.h>
12#include <pthread.h>
13#include <signal.h>
14#include <assert.h>
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15#include <stdlib.h>
16#include <string.h>
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17
18#include "urcu.h"
19
20pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
21
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22/*
23 * Global grace period counter.
24 * Contains the current RCU_GP_CTR_BIT.
25 * Also has a RCU_GP_CTR_BIT of 1, to accelerate the reader fast path.
26 */
27long urcu_gp_ctr = RCU_GP_COUNT;
27b012e2 28
6e8b8429 29long __thread urcu_active_readers;
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30
31/* Thread IDs of registered readers */
32#define INIT_NUM_THREADS 4
33
34struct reader_data {
35 pthread_t tid;
128166c9 36 long *urcu_active_readers;
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37};
38
cf380c2f 39#ifdef DEBUG_YIELD
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40unsigned int yield_active;
41unsigned int __thread rand_yield;
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42#endif
43
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44static struct reader_data *reader_data;
45static int num_readers, alloc_readers;
46static int sig_done;
47
c265818b 48void internal_urcu_lock(void)
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49{
50 int ret;
51 ret = pthread_mutex_lock(&urcu_mutex);
52 if (ret) {
53 perror("Error in pthread mutex lock");
54 exit(-1);
55 }
56}
57
c265818b 58void internal_urcu_unlock(void)
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59{
60 int ret;
61
62 ret = pthread_mutex_unlock(&urcu_mutex);
63 if (ret) {
64 perror("Error in pthread mutex unlock");
65 exit(-1);
66 }
67}
68
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69/*
70 * called with urcu_mutex held.
71 */
1430ee0b 72static void switch_next_urcu_qparity(void)
27b012e2 73{
1430ee0b 74 urcu_gp_ctr ^= RCU_GP_CTR_BIT;
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75}
76
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77#ifdef DEBUG_FULL_MB
78static void force_mb_all_threads(void)
79{
80 mb();
81}
82#else
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83static void force_mb_all_threads(void)
84{
f69f195a 85 struct reader_data *index;
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86 /*
87 * Ask for each threads to execute a mb() so we can consider the
88 * compiler barriers around rcu read lock as real memory barriers.
89 */
90 if (!reader_data)
91 return;
cf380c2f 92 debug_yield_write();
27b012e2 93 sig_done = 0;
cf380c2f 94 debug_yield_write();
f69f195a 95 mb(); /* write sig_done before sending the signals */
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96 debug_yield_write();
97 for (index = reader_data; index < reader_data + num_readers; index++) {
f69f195a 98 pthread_kill(index->tid, SIGURCU);
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99 debug_yield_write();
100 }
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101 /*
102 * Wait for sighandler (and thus mb()) to execute on every thread.
103 * BUSY-LOOP.
104 */
105 while (sig_done < num_readers)
106 barrier();
cf380c2f 107 debug_yield_write();
f69f195a 108 mb(); /* read sig_done before ending the barrier */
cf380c2f 109 debug_yield_write();
27b012e2 110}
bb488185 111#endif
27b012e2 112
1430ee0b 113void wait_for_quiescent_state(void)
27b012e2 114{
f69f195a 115 struct reader_data *index;
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116
117 if (!reader_data)
118 return;
119 /* Wait for each thread urcu_active_readers count to become 0.
120 */
f69f195a 121 for (index = reader_data; index < reader_data + num_readers; index++) {
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122 /*
123 * BUSY-LOOP.
124 */
1430ee0b 125 while (rcu_old_gp_ongoing(index->urcu_active_readers))
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126 barrier();
127 }
128 /*
129 * Locally : read *index->urcu_active_readers before freeing old
130 * pointer.
131 * Remote (reader threads) : Order urcu_qparity update and other
132 * thread's quiescent state counter read.
133 */
134 force_mb_all_threads();
135}
136
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137static void switch_qparity(void)
138{
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139 /* All threads should read qparity before accessing data structure. */
140 /* Write ptr before changing the qparity */
141 force_mb_all_threads();
cf380c2f 142 debug_yield_write();
1430ee0b 143 switch_next_urcu_qparity();
cf380c2f 144 debug_yield_write();
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145
146 /*
147 * Wait for previous parity to be empty of readers.
148 */
1430ee0b 149 wait_for_quiescent_state();
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150}
151
152void synchronize_rcu(void)
153{
cf380c2f 154 debug_yield_write();
c265818b 155 internal_urcu_lock();
cf380c2f 156 debug_yield_write();
2bc59bd7 157 switch_qparity();
cf380c2f 158 debug_yield_write();
2bc59bd7 159 switch_qparity();
cf380c2f 160 debug_yield_write();
e7b43771 161 internal_urcu_unlock();
cf380c2f 162 debug_yield_write();
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163}
164
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165void urcu_add_reader(pthread_t id)
166{
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167 struct reader_data *oldarray;
168
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169 if (!reader_data) {
170 alloc_readers = INIT_NUM_THREADS;
f69f195a 171 num_readers = 0;
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172 reader_data =
173 malloc(sizeof(struct reader_data) * alloc_readers);
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174 }
175 if (alloc_readers < num_readers + 1) {
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176 oldarray = reader_data;
177 reader_data = malloc(sizeof(struct reader_data)
178 * (alloc_readers << 1));
179 memcpy(reader_data, oldarray,
180 sizeof(struct reader_data) * alloc_readers);
181 alloc_readers <<= 1;
182 free(oldarray);
183 }
184 reader_data[num_readers].tid = id;
185 /* reference to the TLS of _this_ reader thread. */
1430ee0b 186 reader_data[num_readers].urcu_active_readers = &urcu_active_readers;
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187 num_readers++;
188}
189
190/*
191 * Never shrink (implementation limitation).
192 * This is O(nb threads). Eventually use a hash table.
193 */
194void urcu_remove_reader(pthread_t id)
195{
196 struct reader_data *index;
197
198 assert(reader_data != NULL);
199 for (index = reader_data; index < reader_data + num_readers; index++) {
e6d6e2dc 200 if (pthread_equal(index->tid, id)) {
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201 memcpy(index, &reader_data[num_readers - 1],
202 sizeof(struct reader_data));
203 reader_data[num_readers - 1].tid = 0;
204 reader_data[num_readers - 1].urcu_active_readers = NULL;
205 num_readers--;
206 return;
207 }
208 }
209 /* Hrm not found, forgot to register ? */
210 assert(0);
211}
212
213void urcu_register_thread(void)
214{
c265818b 215 internal_urcu_lock();
41718ff9 216 urcu_add_reader(pthread_self());
c265818b 217 internal_urcu_unlock();
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218}
219
f69f195a 220void urcu_unregister_thread(void)
27b012e2 221{
c265818b 222 internal_urcu_lock();
41718ff9 223 urcu_remove_reader(pthread_self());
c265818b 224 internal_urcu_unlock();
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225}
226
bb488185 227#ifndef DEBUG_FULL_MB
f69f195a 228void sigurcu_handler(int signo, siginfo_t *siginfo, void *context)
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229{
230 mb();
231 atomic_inc(&sig_done);
232}
233
234void __attribute__((constructor)) urcu_init(void)
235{
236 struct sigaction act;
237 int ret;
238
239 act.sa_sigaction = sigurcu_handler;
240 ret = sigaction(SIGURCU, &act, NULL);
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241 if (ret) {
242 perror("Error in sigaction");
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243 exit(-1);
244 }
245}
246
247void __attribute__((destructor)) urcu_exit(void)
248{
249 struct sigaction act;
250 int ret;
251
252 ret = sigaction(SIGURCU, NULL, &act);
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253 if (ret) {
254 perror("Error in sigaction");
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255 exit(-1);
256 }
257 assert(act.sa_sigaction == sigurcu_handler);
258 free(reader_data);
259}
bb488185 260#endif
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