2 * Copyright (c) 2014 Nicira, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at:
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
19 #include "guarded-list.h"
21 #include "ovs-thread.h"
22 #include "poll-loop.h"
27 VLOG_DEFINE_THIS_MODULE(ovs_rcu);
30 void (*function)(void *aux);
35 struct list list_node;
36 struct ovsrcu_cb cbs[16];
40 struct ovsrcu_perthread {
41 struct list list_node; /* In global list. */
43 struct ovs_mutex mutex;
45 struct ovsrcu_cbset *cbset;
46 char name[16]; /* This thread's name. */
49 static struct seq *global_seqno;
51 static pthread_key_t perthread_key;
52 static struct list ovsrcu_threads;
53 static struct ovs_mutex ovsrcu_threads_mutex;
55 static struct guarded_list flushed_cbsets;
56 static struct seq *flushed_cbsets_seq;
58 static void ovsrcu_init_module(void);
59 static void ovsrcu_flush_cbset(struct ovsrcu_perthread *);
60 static void ovsrcu_unregister__(struct ovsrcu_perthread *);
61 static bool ovsrcu_call_postponed(void);
62 static void *ovsrcu_postpone_thread(void *arg OVS_UNUSED);
64 static struct ovsrcu_perthread *
65 ovsrcu_perthread_get(void)
67 struct ovsrcu_perthread *perthread;
71 perthread = pthread_getspecific(perthread_key);
73 const char *name = get_subprogram_name();
75 perthread = xmalloc(sizeof *perthread);
76 ovs_mutex_init(&perthread->mutex);
77 perthread->seqno = seq_read(global_seqno);
78 perthread->cbset = NULL;
79 ovs_strlcpy(perthread->name, name[0] ? name : "main",
80 sizeof perthread->name);
82 ovs_mutex_lock(&ovsrcu_threads_mutex);
83 list_push_back(&ovsrcu_threads, &perthread->list_node);
84 ovs_mutex_unlock(&ovsrcu_threads_mutex);
86 pthread_setspecific(perthread_key, perthread);
91 /* Indicates the end of a quiescent state. See "Details" near the top of
94 * Quiescent states don't stack or nest, so this always ends a quiescent state
95 * even if ovsrcu_quiesce_start() was called multiple times in a row. */
97 ovsrcu_quiesce_end(void)
99 ovsrcu_perthread_get();
103 ovsrcu_quiesced(void)
105 if (single_threaded()) {
106 ovsrcu_call_postponed();
108 static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
109 if (ovsthread_once_start(&once)) {
110 ovs_thread_create("urcu", ovsrcu_postpone_thread, NULL);
111 ovsthread_once_done(&once);
116 /* Indicates the beginning of a quiescent state. See "Details" near the top of
119 ovsrcu_quiesce_start(void)
121 struct ovsrcu_perthread *perthread;
123 ovsrcu_init_module();
124 perthread = pthread_getspecific(perthread_key);
126 pthread_setspecific(perthread_key, NULL);
127 ovsrcu_unregister__(perthread);
133 /* Indicates a momentary quiescent state. See "Details" near the top of
136 * Provides a full memory barrier via seq_change().
141 struct ovsrcu_perthread *perthread;
143 perthread = ovsrcu_perthread_get();
144 perthread->seqno = seq_read(global_seqno);
145 if (perthread->cbset) {
146 ovsrcu_flush_cbset(perthread);
148 seq_change(global_seqno);
154 ovsrcu_is_quiescent(void)
156 ovsrcu_init_module();
157 return pthread_getspecific(perthread_key) == NULL;
161 ovsrcu_synchronize(void)
163 unsigned int warning_threshold = 1000;
164 uint64_t target_seqno;
167 if (single_threaded()) {
171 target_seqno = seq_read(global_seqno);
172 ovsrcu_quiesce_start();
176 uint64_t cur_seqno = seq_read(global_seqno);
177 struct ovsrcu_perthread *perthread;
178 char stalled_thread[16];
179 unsigned int elapsed;
182 ovs_mutex_lock(&ovsrcu_threads_mutex);
183 LIST_FOR_EACH (perthread, list_node, &ovsrcu_threads) {
184 if (perthread->seqno <= target_seqno) {
185 ovs_strlcpy(stalled_thread, perthread->name,
186 sizeof stalled_thread);
191 ovs_mutex_unlock(&ovsrcu_threads_mutex);
197 elapsed = time_msec() - start;
198 if (elapsed >= warning_threshold) {
199 VLOG_WARN("blocked %u ms waiting for %s to quiesce",
200 elapsed, stalled_thread);
201 warning_threshold *= 2;
203 poll_timer_wait_until(start + warning_threshold);
205 seq_wait(global_seqno, cur_seqno);
208 ovsrcu_quiesce_end();
211 /* Registers 'function' to be called, passing 'aux' as argument, after the
214 * This function is more conveniently called through the ovsrcu_postpone()
215 * macro, which provides a type-safe way to allow 'function''s parameter to be
216 * any pointer type. */
218 ovsrcu_postpone__(void (*function)(void *aux), void *aux)
220 struct ovsrcu_perthread *perthread = ovsrcu_perthread_get();
221 struct ovsrcu_cbset *cbset;
222 struct ovsrcu_cb *cb;
224 cbset = perthread->cbset;
226 cbset = perthread->cbset = xmalloc(sizeof *perthread->cbset);
230 cb = &cbset->cbs[cbset->n_cbs++];
231 cb->function = function;
234 if (cbset->n_cbs >= ARRAY_SIZE(cbset->cbs)) {
235 ovsrcu_flush_cbset(perthread);
240 ovsrcu_call_postponed(void)
242 struct ovsrcu_cbset *cbset, *next_cbset;
245 guarded_list_pop_all(&flushed_cbsets, &cbsets);
246 if (list_is_empty(&cbsets)) {
250 ovsrcu_synchronize();
252 LIST_FOR_EACH_SAFE (cbset, next_cbset, list_node, &cbsets) {
253 struct ovsrcu_cb *cb;
255 for (cb = cbset->cbs; cb < &cbset->cbs[cbset->n_cbs]; cb++) {
256 cb->function(cb->aux);
258 list_remove(&cbset->list_node);
266 ovsrcu_postpone_thread(void *arg OVS_UNUSED)
268 pthread_detach(pthread_self());
271 uint64_t seqno = seq_read(flushed_cbsets_seq);
272 if (!ovsrcu_call_postponed()) {
273 seq_wait(flushed_cbsets_seq, seqno);
282 ovsrcu_flush_cbset(struct ovsrcu_perthread *perthread)
284 struct ovsrcu_cbset *cbset = perthread->cbset;
287 guarded_list_push_back(&flushed_cbsets, &cbset->list_node, SIZE_MAX);
288 perthread->cbset = NULL;
290 seq_change(flushed_cbsets_seq);
295 ovsrcu_unregister__(struct ovsrcu_perthread *perthread)
297 if (perthread->cbset) {
298 ovsrcu_flush_cbset(perthread);
301 ovs_mutex_lock(&ovsrcu_threads_mutex);
302 list_remove(&perthread->list_node);
303 ovs_mutex_unlock(&ovsrcu_threads_mutex);
305 ovs_mutex_destroy(&perthread->mutex);
308 seq_change(global_seqno);
312 ovsrcu_thread_exit_cb(void *perthread)
314 ovsrcu_unregister__(perthread);
318 ovsrcu_init_module(void)
320 static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
321 if (ovsthread_once_start(&once)) {
322 global_seqno = seq_create();
323 xpthread_key_create(&perthread_key, ovsrcu_thread_exit_cb);
324 list_init(&ovsrcu_threads);
325 ovs_mutex_init(&ovsrcu_threads_mutex);
327 guarded_list_init(&flushed_cbsets);
328 flushed_cbsets_seq = seq_create();
330 ovsthread_once_done(&once);