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(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);
63 static void ovsrcu_synchronize(void);
65 static struct ovsrcu_perthread *
66 ovsrcu_perthread_get(void)
68 struct ovsrcu_perthread *perthread;
72 perthread = pthread_getspecific(perthread_key);
74 const char *name = get_subprogram_name();
76 perthread = xmalloc(sizeof *perthread);
77 ovs_mutex_init(&perthread->mutex);
78 perthread->seqno = seq_read(global_seqno);
79 perthread->cbset = NULL;
80 ovs_strlcpy(perthread->name, name[0] ? name : "main",
81 sizeof perthread->name);
83 ovs_mutex_lock(&ovsrcu_threads_mutex);
84 list_push_back(&ovsrcu_threads, &perthread->list_node);
85 ovs_mutex_unlock(&ovsrcu_threads_mutex);
87 pthread_setspecific(perthread_key, perthread);
92 /* Indicates the end of a quiescent state. See "Details" near the top of
95 * Quiescent states don't stack or nest, so this always ends a quiescent state
96 * even if ovsrcu_quiesce_start() was called multiple times in a row. */
98 ovsrcu_quiesce_end(void)
100 ovsrcu_perthread_get();
104 ovsrcu_quiesced(void)
106 if (single_threaded()) {
107 ovsrcu_call_postponed();
109 static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
110 if (ovsthread_once_start(&once)) {
111 ovs_thread_create("urcu", ovsrcu_postpone_thread, NULL);
112 ovsthread_once_done(&once);
117 /* Indicates the beginning of a quiescent state. See "Details" near the top of
120 ovsrcu_quiesce_start(void)
122 struct ovsrcu_perthread *perthread;
125 perthread = pthread_getspecific(perthread_key);
127 pthread_setspecific(perthread_key, NULL);
128 ovsrcu_unregister__(perthread);
134 /* Indicates a momentary quiescent state. See "Details" near the top of
140 ovsrcu_perthread_get()->seqno = seq_read(global_seqno);
141 seq_change(global_seqno);
147 ovsrcu_is_quiescent(void)
150 return pthread_getspecific(perthread_key) == NULL;
154 ovsrcu_synchronize(void)
156 unsigned int warning_threshold = 1000;
157 uint64_t target_seqno;
160 if (single_threaded()) {
164 target_seqno = seq_read(global_seqno);
165 ovsrcu_quiesce_start();
169 uint64_t cur_seqno = seq_read(global_seqno);
170 struct ovsrcu_perthread *perthread;
171 char stalled_thread[16];
172 unsigned int elapsed;
175 ovs_mutex_lock(&ovsrcu_threads_mutex);
176 LIST_FOR_EACH (perthread, list_node, &ovsrcu_threads) {
177 if (perthread->seqno <= target_seqno) {
178 ovs_strlcpy(stalled_thread, perthread->name,
179 sizeof stalled_thread);
184 ovs_mutex_unlock(&ovsrcu_threads_mutex);
190 elapsed = time_msec() - start;
191 if (elapsed >= warning_threshold) {
192 VLOG_WARN("blocked %u ms waiting for %s to quiesce",
193 elapsed, stalled_thread);
194 warning_threshold *= 2;
196 poll_timer_wait_until(start + warning_threshold);
198 seq_wait(global_seqno, cur_seqno);
201 ovsrcu_quiesce_end();
204 /* Registers 'function' to be called, passing 'aux' as argument, after the
207 * This function is more conveniently called through the ovsrcu_postpone()
208 * macro, which provides a type-safe way to allow 'function''s parameter to be
209 * any pointer type. */
211 ovsrcu_postpone__(void (*function)(void *aux), void *aux)
213 struct ovsrcu_perthread *perthread = ovsrcu_perthread_get();
214 struct ovsrcu_cbset *cbset;
215 struct ovsrcu_cb *cb;
217 cbset = perthread->cbset;
219 cbset = perthread->cbset = xmalloc(sizeof *perthread->cbset);
223 cb = &cbset->cbs[cbset->n_cbs++];
224 cb->function = function;
227 if (cbset->n_cbs >= ARRAY_SIZE(cbset->cbs)) {
228 ovsrcu_flush_cbset(perthread);
233 ovsrcu_call_postponed(void)
235 struct ovsrcu_cbset *cbset, *next_cbset;
238 guarded_list_pop_all(&flushed_cbsets, &cbsets);
239 if (list_is_empty(&cbsets)) {
243 ovsrcu_synchronize();
245 LIST_FOR_EACH_SAFE (cbset, next_cbset, list_node, &cbsets) {
246 struct ovsrcu_cb *cb;
248 for (cb = cbset->cbs; cb < &cbset->cbs[cbset->n_cbs]; cb++) {
249 cb->function(cb->aux);
251 list_remove(&cbset->list_node);
259 ovsrcu_postpone_thread(void *arg OVS_UNUSED)
261 pthread_detach(pthread_self());
264 uint64_t seqno = seq_read(flushed_cbsets_seq);
265 if (!ovsrcu_call_postponed()) {
266 seq_wait(flushed_cbsets_seq, seqno);
275 ovsrcu_flush_cbset(struct ovsrcu_perthread *perthread)
277 struct ovsrcu_cbset *cbset = perthread->cbset;
280 guarded_list_push_back(&flushed_cbsets, &cbset->list_node, SIZE_MAX);
281 perthread->cbset = NULL;
283 seq_change(flushed_cbsets_seq);
288 ovsrcu_unregister__(struct ovsrcu_perthread *perthread)
290 if (perthread->cbset) {
291 ovsrcu_flush_cbset(perthread);
294 ovs_mutex_lock(&ovsrcu_threads_mutex);
295 list_remove(&perthread->list_node);
296 ovs_mutex_unlock(&ovsrcu_threads_mutex);
298 ovs_mutex_destroy(&perthread->mutex);
301 seq_change(global_seqno);
305 ovsrcu_thread_exit_cb(void *perthread)
307 ovsrcu_unregister__(perthread);
313 static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
314 if (ovsthread_once_start(&once)) {
315 global_seqno = seq_create();
316 xpthread_key_create(&perthread_key, ovsrcu_thread_exit_cb);
317 list_init(&ovsrcu_threads);
318 ovs_mutex_init(&ovsrcu_threads_mutex);
320 guarded_list_init(&flushed_cbsets);
321 flushed_cbsets_seq = seq_create();
323 ovsthread_once_done(&once);