1/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
2 *
3 * Permission is hereby granted, free of charge, to any person obtaining a copy
4 * of this software and associated documentation files (the "Software"), to
5 * deal in the Software without restriction, including without limitation the
6 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
7 * sell copies of the Software, and to permit persons to whom the Software is
8 * furnished to do so, subject to the following conditions:
9 *
10 * The above copyright notice and this permission notice shall be included in
11 * all copies or substantial portions of the Software.
12 *
13 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
14 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
15 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
16 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
17 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
18 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
19 * IN THE SOFTWARE.
20 */
21
22#include "uv-common.h"
23
24#if !defined(_WIN32)
25# include "unix/internal.h"
26#endif
27
28#include <stdlib.h>
29
30#define MAX_THREADPOOL_SIZE 1024
31
32static uv_once_t once = UV_ONCE_INIT;
33static uv_cond_t cond;
34static uv_mutex_t mutex;
35static unsigned int idle_threads;
36static unsigned int slow_io_work_running;
37static unsigned int nthreads;
38static uv_thread_t* threads;
39static uv_thread_t default_threads[4];
40static QUEUE exit_message;
41static QUEUE wq;
42static QUEUE run_slow_work_message;
43static QUEUE slow_io_pending_wq;
44
45static unsigned int slow_work_thread_threshold(void) {
46 return (nthreads + 1) / 2;
47}
48
49static void uv__cancelled(struct uv__work* w) {
50 abort();
51}
52
53
54/* To avoid deadlock with uv_cancel() it's crucial that the worker
55 * never holds the global mutex and the loop-local mutex at the same time.
56 */
57static void worker(void* arg) {
58 struct uv__work* w;
59 QUEUE* q;
60 int is_slow_work;
61
62 uv_sem_post((uv_sem_t*) arg);
63 arg = NULL;
64
65 uv_mutex_lock(&mutex);
66 for (;;) {
67 /* `mutex` should always be locked at this point. */
68
69 /* Keep waiting while either no work is present or only slow I/O
70 and we're at the threshold for that. */
71 while (QUEUE_EMPTY(&wq) ||
72 (QUEUE_HEAD(&wq) == &run_slow_work_message &&
73 QUEUE_NEXT(&run_slow_work_message) == &wq &&
74 slow_io_work_running >= slow_work_thread_threshold())) {
75 idle_threads += 1;
76 uv_cond_wait(&cond, &mutex);
77 idle_threads -= 1;
78 }
79
80 q = QUEUE_HEAD(&wq);
81 if (q == &exit_message) {
82 uv_cond_signal(&cond);
83 uv_mutex_unlock(&mutex);
84 break;
85 }
86
87 QUEUE_REMOVE(q);
88 QUEUE_INIT(q); /* Signal uv_cancel() that the work req is executing. */
89
90 is_slow_work = 0;
91 if (q == &run_slow_work_message) {
92 /* If we're at the slow I/O threshold, re-schedule until after all
93 other work in the queue is done. */
94 if (slow_io_work_running >= slow_work_thread_threshold()) {
95 QUEUE_INSERT_TAIL(&wq, q);
96 continue;
97 }
98
99 /* If we encountered a request to run slow I/O work but there is none
100 to run, that means it's cancelled => Start over. */
101 if (QUEUE_EMPTY(&slow_io_pending_wq))
102 continue;
103
104 is_slow_work = 1;
105 slow_io_work_running++;
106
107 q = QUEUE_HEAD(&slow_io_pending_wq);
108 QUEUE_REMOVE(q);
109 QUEUE_INIT(q);
110
111 /* If there is more slow I/O work, schedule it to be run as well. */
112 if (!QUEUE_EMPTY(&slow_io_pending_wq)) {
113 QUEUE_INSERT_TAIL(&wq, &run_slow_work_message);
114 if (idle_threads > 0)
115 uv_cond_signal(&cond);
116 }
117 }
118
119 uv_mutex_unlock(&mutex);
120
121 w = QUEUE_DATA(q, struct uv__work, wq);
122 w->work(w);
123
124 uv_mutex_lock(&w->loop->wq_mutex);
125 w->work = NULL; /* Signal uv_cancel() that the work req is done
126 executing. */
127 QUEUE_INSERT_TAIL(&w->loop->wq, &w->wq);
128 uv_async_send(&w->loop->wq_async);
129 uv_mutex_unlock(&w->loop->wq_mutex);
130
131 /* Lock `mutex` since that is expected at the start of the next
132 * iteration. */
133 uv_mutex_lock(&mutex);
134 if (is_slow_work) {
135 /* `slow_io_work_running` is protected by `mutex`. */
136 slow_io_work_running--;
137 }
138 }
139}
140
141
142static void post(QUEUE* q, enum uv__work_kind kind) {
143 uv_mutex_lock(&mutex);
144 if (kind == UV__WORK_SLOW_IO) {
145 /* Insert into a separate queue. */
146 QUEUE_INSERT_TAIL(&slow_io_pending_wq, q);
147 if (!QUEUE_EMPTY(&run_slow_work_message)) {
148 /* Running slow I/O tasks is already scheduled => Nothing to do here.
149 The worker that runs said other task will schedule this one as well. */
150 uv_mutex_unlock(&mutex);
151 return;
152 }
153 q = &run_slow_work_message;
154 }
155
156 QUEUE_INSERT_TAIL(&wq, q);
157 if (idle_threads > 0)
158 uv_cond_signal(&cond);
159 uv_mutex_unlock(&mutex);
160}
161
162
163#ifndef _WIN32
164UV_DESTRUCTOR(static void cleanup(void)) {
165 unsigned int i;
166
167 if (nthreads == 0)
168 return;
169
170 post(&exit_message, UV__WORK_CPU);
171
172 for (i = 0; i < nthreads; i++)
173 if (uv_thread_join(threads + i))
174 abort();
175
176 if (threads != default_threads)
177 uv__free(threads);
178
179 uv_mutex_destroy(&mutex);
180 uv_cond_destroy(&cond);
181
182 threads = NULL;
183 nthreads = 0;
184}
185#endif
186
187
188static void init_threads(void) {
189 unsigned int i;
190 const char* val;
191 uv_sem_t sem;
192
193 nthreads = ARRAY_SIZE(default_threads);
194 val = getenv("UV_THREADPOOL_SIZE");
195 if (val != NULL)
196 nthreads = atoi(val);
197 if (nthreads == 0)
198 nthreads = 1;
199 if (nthreads > MAX_THREADPOOL_SIZE)
200 nthreads = MAX_THREADPOOL_SIZE;
201
202 threads = default_threads;
203 if (nthreads > ARRAY_SIZE(default_threads)) {
204 threads = uv__malloc(nthreads * sizeof(threads[0]));
205 if (threads == NULL) {
206 nthreads = ARRAY_SIZE(default_threads);
207 threads = default_threads;
208 }
209 }
210
211 if (uv_cond_init(&cond))
212 abort();
213
214 if (uv_mutex_init(&mutex))
215 abort();
216
217 QUEUE_INIT(&wq);
218 QUEUE_INIT(&slow_io_pending_wq);
219 QUEUE_INIT(&run_slow_work_message);
220
221 if (uv_sem_init(&sem, 0))
222 abort();
223
224 for (i = 0; i < nthreads; i++)
225 if (uv_thread_create(threads + i, worker, &sem))
226 abort();
227
228 for (i = 0; i < nthreads; i++)
229 uv_sem_wait(&sem);
230
231 uv_sem_destroy(&sem);
232}
233
234
235#ifndef _WIN32
236static void reset_once(void) {
237 uv_once_t child_once = UV_ONCE_INIT;
238 memcpy(&once, &child_once, sizeof(child_once));
239}
240#endif
241
242
243static void init_once(void) {
244#ifndef _WIN32
245 /* Re-initialize the threadpool after fork.
246 * Note that this discards the global mutex and condition as well
247 * as the work queue.
248 */
249 if (pthread_atfork(NULL, NULL, &reset_once))
250 abort();
251#endif
252 init_threads();
253}
254
255
256void uv__work_submit(uv_loop_t* loop,
257 struct uv__work* w,
258 enum uv__work_kind kind,
259 void (*work)(struct uv__work* w),
260 void (*done)(struct uv__work* w, int status)) {
261 uv_once(&once, init_once);
262 w->loop = loop;
263 w->work = work;
264 w->done = done;
265 post(&w->wq, kind);
266}
267
268
269static int uv__work_cancel(uv_loop_t* loop, uv_req_t* req, struct uv__work* w) {
270 int cancelled;
271
272 uv_mutex_lock(&mutex);
273 uv_mutex_lock(&w->loop->wq_mutex);
274
275 cancelled = !QUEUE_EMPTY(&w->wq) && w->work != NULL;
276 if (cancelled)
277 QUEUE_REMOVE(&w->wq);
278
279 uv_mutex_unlock(&w->loop->wq_mutex);
280 uv_mutex_unlock(&mutex);
281
282 if (!cancelled)
283 return UV_EBUSY;
284
285 w->work = uv__cancelled;
286 uv_mutex_lock(&loop->wq_mutex);
287 QUEUE_INSERT_TAIL(&loop->wq, &w->wq);
288 uv_async_send(&loop->wq_async);
289 uv_mutex_unlock(&loop->wq_mutex);
290
291 return 0;
292}
293
294
295void uv__work_done(uv_async_t* handle) {
296 struct uv__work* w;
297 uv_loop_t* loop;
298 QUEUE* q;
299 QUEUE wq;
300 int err;
301
302 loop = container_of(handle, uv_loop_t, wq_async);
303 uv_mutex_lock(&loop->wq_mutex);
304 QUEUE_MOVE(&loop->wq, &wq);
305 uv_mutex_unlock(&loop->wq_mutex);
306
307 while (!QUEUE_EMPTY(&wq)) {
308 q = QUEUE_HEAD(&wq);
309 QUEUE_REMOVE(q);
310
311 w = container_of(q, struct uv__work, wq);
312 err = (w->work == uv__cancelled) ? UV_ECANCELED : 0;
313 w->done(w, err);
314 }
315}
316
317
318static void uv__queue_work(struct uv__work* w) {
319 uv_work_t* req = container_of(w, uv_work_t, work_req);
320
321 req->work_cb(req);
322}
323
324
325static void uv__queue_done(struct uv__work* w, int err) {
326 uv_work_t* req;
327
328 req = container_of(w, uv_work_t, work_req);
329 uv__req_unregister(req->loop, req);
330
331 if (req->after_work_cb == NULL)
332 return;
333
334 req->after_work_cb(req, err);
335}
336
337
338int uv_queue_work(uv_loop_t* loop,
339 uv_work_t* req,
340 uv_work_cb work_cb,
341 uv_after_work_cb after_work_cb) {
342 if (work_cb == NULL)
343 return UV_EINVAL;
344
345 uv__req_init(loop, req, UV_WORK);
346 req->loop = loop;
347 req->work_cb = work_cb;
348 req->after_work_cb = after_work_cb;
349 uv__work_submit(loop,
350 &req->work_req,
351 UV__WORK_CPU,
352 uv__queue_work,
353 uv__queue_done);
354 return 0;
355}
356
357
358int uv_cancel(uv_req_t* req) {
359 struct uv__work* wreq;
360 uv_loop_t* loop;
361
362 switch (req->type) {
363 case UV_FS:
364 loop = ((uv_fs_t*) req)->loop;
365 wreq = &((uv_fs_t*) req)->work_req;
366 break;
367 case UV_GETADDRINFO:
368 loop = ((uv_getaddrinfo_t*) req)->loop;
369 wreq = &((uv_getaddrinfo_t*) req)->work_req;
370 break;
371 case UV_GETNAMEINFO:
372 loop = ((uv_getnameinfo_t*) req)->loop;
373 wreq = &((uv_getnameinfo_t*) req)->work_req;
374 break;
375 case UV_WORK:
376 loop = ((uv_work_t*) req)->loop;
377 wreq = &((uv_work_t*) req)->work_req;
378 break;
379 default:
380 return UV_EINVAL;
381 }
382
383 return uv__work_cancel(loop, req, wreq);
384}
385