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 "fatal-signal.h"
20 #include "guarded-list.h"
22 #include "ovs-thread.h"
23 #include "poll-loop.h"
26 #include "openvswitch/vlog.h"
28 VLOG_DEFINE_THIS_MODULE(ovs_rcu);
31 void (*function)(void *aux);
36 struct ovs_list list_node;
37 struct ovsrcu_cb cbs[16];
41 struct ovsrcu_perthread {
42 struct ovs_list list_node; /* In global list. */
44 struct ovs_mutex mutex;
46 struct ovsrcu_cbset *cbset;
47 char name[16]; /* This thread's name. */
50 static struct seq *global_seqno;
52 static pthread_key_t perthread_key;
53 static struct ovs_list ovsrcu_threads;
54 static struct ovs_mutex ovsrcu_threads_mutex;
56 static struct guarded_list flushed_cbsets;
57 static struct seq *flushed_cbsets_seq;
59 static void ovsrcu_init_module(void);
60 static void ovsrcu_flush_cbset(struct ovsrcu_perthread *);
61 static void ovsrcu_unregister__(struct ovsrcu_perthread *);
62 static bool ovsrcu_call_postponed(void);
63 static void *ovsrcu_postpone_thread(void *arg OVS_UNUSED);
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;
124 ovsrcu_init_module();
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
137 * Provides a full memory barrier via seq_change().
142 struct ovsrcu_perthread *perthread;
144 perthread = ovsrcu_perthread_get();
145 perthread->seqno = seq_read(global_seqno);
146 if (perthread->cbset) {
147 ovsrcu_flush_cbset(perthread);
149 seq_change(global_seqno);
155 ovsrcu_is_quiescent(void)
157 ovsrcu_init_module();
158 return pthread_getspecific(perthread_key) == NULL;
162 ovsrcu_synchronize(void)
164 unsigned int warning_threshold = 1000;
165 uint64_t target_seqno;
168 if (single_threaded()) {
172 target_seqno = seq_read(global_seqno);
173 ovsrcu_quiesce_start();
177 uint64_t cur_seqno = seq_read(global_seqno);
178 struct ovsrcu_perthread *perthread;
179 char stalled_thread[16];
180 unsigned int elapsed;
183 ovs_mutex_lock(&ovsrcu_threads_mutex);
184 LIST_FOR_EACH (perthread, list_node, &ovsrcu_threads) {
185 if (perthread->seqno <= target_seqno) {
186 ovs_strlcpy(stalled_thread, perthread->name,
187 sizeof stalled_thread);
192 ovs_mutex_unlock(&ovsrcu_threads_mutex);
198 elapsed = time_msec() - start;
199 if (elapsed >= warning_threshold) {
200 VLOG_WARN("blocked %u ms waiting for %s to quiesce",
201 elapsed, stalled_thread);
202 warning_threshold *= 2;
204 poll_timer_wait_until(start + warning_threshold);
206 seq_wait(global_seqno, cur_seqno);
209 ovsrcu_quiesce_end();
212 /* Registers 'function' to be called, passing 'aux' as argument, after the
215 * The call is guaranteed to happen after the next time all participating
216 * threads have quiesced at least once, but there is no quarantee that all
217 * registered functions are called as early as possible, or that the functions
218 * registered by different threads would be called in the order the
219 * registrations took place. In particular, even if two threads provably
220 * register a function each in a specific order, the functions may still be
221 * called in the opposite order, depending on the timing of when the threads
222 * call ovsrcu_quiesce(), how many functions they postpone, and when the
223 * ovs-rcu thread happens to grab the functions to be called.
225 * All functions registered by a single thread are guaranteed to execute in the
226 * registering order, however.
228 * This function is more conveniently called through the ovsrcu_postpone()
229 * macro, which provides a type-safe way to allow 'function''s parameter to be
230 * any pointer type. */
232 ovsrcu_postpone__(void (*function)(void *aux), void *aux)
234 struct ovsrcu_perthread *perthread = ovsrcu_perthread_get();
235 struct ovsrcu_cbset *cbset;
236 struct ovsrcu_cb *cb;
238 cbset = perthread->cbset;
240 cbset = perthread->cbset = xmalloc(sizeof *perthread->cbset);
244 cb = &cbset->cbs[cbset->n_cbs++];
245 cb->function = function;
248 if (cbset->n_cbs >= ARRAY_SIZE(cbset->cbs)) {
249 ovsrcu_flush_cbset(perthread);
254 ovsrcu_call_postponed(void)
256 struct ovsrcu_cbset *cbset;
257 struct ovs_list cbsets;
259 guarded_list_pop_all(&flushed_cbsets, &cbsets);
260 if (list_is_empty(&cbsets)) {
264 ovsrcu_synchronize();
266 LIST_FOR_EACH_POP (cbset, list_node, &cbsets) {
267 struct ovsrcu_cb *cb;
269 for (cb = cbset->cbs; cb < &cbset->cbs[cbset->n_cbs]; cb++) {
270 cb->function(cb->aux);
279 ovsrcu_postpone_thread(void *arg OVS_UNUSED)
281 pthread_detach(pthread_self());
284 uint64_t seqno = seq_read(flushed_cbsets_seq);
285 if (!ovsrcu_call_postponed()) {
286 seq_wait(flushed_cbsets_seq, seqno);
295 ovsrcu_flush_cbset(struct ovsrcu_perthread *perthread)
297 struct ovsrcu_cbset *cbset = perthread->cbset;
300 guarded_list_push_back(&flushed_cbsets, &cbset->list_node, SIZE_MAX);
301 perthread->cbset = NULL;
303 seq_change(flushed_cbsets_seq);
308 ovsrcu_unregister__(struct ovsrcu_perthread *perthread)
310 if (perthread->cbset) {
311 ovsrcu_flush_cbset(perthread);
314 ovs_mutex_lock(&ovsrcu_threads_mutex);
315 list_remove(&perthread->list_node);
316 ovs_mutex_unlock(&ovsrcu_threads_mutex);
318 ovs_mutex_destroy(&perthread->mutex);
321 seq_change(global_seqno);
325 ovsrcu_thread_exit_cb(void *perthread)
327 ovsrcu_unregister__(perthread);
330 /* Cancels the callback to ovsrcu_thread_exit_cb().
332 * Cancelling the call to the destructor during the main thread exit
333 * is needed while using pthreads-win32 library in Windows. It has been
334 * observed that in pthreads-win32, a call to the destructor during
335 * main thread exit causes undefined behavior. */
337 ovsrcu_cancel_thread_exit_cb(void *aux OVS_UNUSED)
339 pthread_setspecific(perthread_key, NULL);
343 ovsrcu_init_module(void)
345 static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
346 if (ovsthread_once_start(&once)) {
347 global_seqno = seq_create();
348 xpthread_key_create(&perthread_key, ovsrcu_thread_exit_cb);
349 fatal_signal_add_hook(ovsrcu_cancel_thread_exit_cb, NULL, NULL, true);
350 list_init(&ovsrcu_threads);
351 ovs_mutex_init(&ovsrcu_threads_mutex);
353 guarded_list_init(&flushed_cbsets);
354 flushed_cbsets_seq = seq_create();
356 ovsthread_once_done(&once);