1 /* Copyright libuv project 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.h"
23 #include "internal.h"
24
25 /* POSIX defines poll() as a portable way to wait on file descriptors.
26 * Here we maintain a dynamically sized array of file descriptors and
27 * events to pass as the first argument to poll().
28 */
29
30 #include <assert.h>
31 #include <stddef.h>
32 #include <stdint.h>
33 #include <errno.h>
34 #include <unistd.h>
35
uv__platform_loop_init(uv_loop_t * loop)36 int uv__platform_loop_init(uv_loop_t* loop) {
37 loop->poll_fds = NULL;
38 loop->poll_fds_used = 0;
39 loop->poll_fds_size = 0;
40 loop->poll_fds_iterating = 0;
41 return 0;
42 }
43
uv__platform_loop_delete(uv_loop_t * loop)44 void uv__platform_loop_delete(uv_loop_t* loop) {
45 uv__free(loop->poll_fds);
46 loop->poll_fds = NULL;
47 }
48
uv__io_fork(uv_loop_t * loop)49 int uv__io_fork(uv_loop_t* loop) {
50 uv__platform_loop_delete(loop);
51 return uv__platform_loop_init(loop);
52 }
53
54 /* Allocate or dynamically resize our poll fds array. */
uv__pollfds_maybe_resize(uv_loop_t * loop)55 static void uv__pollfds_maybe_resize(uv_loop_t* loop) {
56 size_t i;
57 size_t n;
58 struct pollfd* p;
59
60 if (loop->poll_fds_used < loop->poll_fds_size)
61 return;
62
63 n = loop->poll_fds_size ? loop->poll_fds_size * 2 : 64;
64 p = uv__reallocf(loop->poll_fds, n * sizeof(*loop->poll_fds));
65 if (p == NULL)
66 abort();
67
68 loop->poll_fds = p;
69 for (i = loop->poll_fds_size; i < n; i++) {
70 loop->poll_fds[i].fd = -1;
71 loop->poll_fds[i].events = 0;
72 loop->poll_fds[i].revents = 0;
73 }
74 loop->poll_fds_size = n;
75 }
76
77 /* Primitive swap operation on poll fds array elements. */
uv__pollfds_swap(uv_loop_t * loop,size_t l,size_t r)78 static void uv__pollfds_swap(uv_loop_t* loop, size_t l, size_t r) {
79 struct pollfd pfd;
80 pfd = loop->poll_fds[l];
81 loop->poll_fds[l] = loop->poll_fds[r];
82 loop->poll_fds[r] = pfd;
83 }
84
85 /* Add a watcher's fd to our poll fds array with its pending events. */
uv__pollfds_add(uv_loop_t * loop,uv__io_t * w)86 static void uv__pollfds_add(uv_loop_t* loop, uv__io_t* w) {
87 size_t i;
88 struct pollfd* pe;
89
90 /* If the fd is already in the set just update its events. */
91 assert(!loop->poll_fds_iterating);
92 for (i = 0; i < loop->poll_fds_used; ++i) {
93 if (loop->poll_fds[i].fd == w->fd) {
94 loop->poll_fds[i].events = w->pevents;
95 return;
96 }
97 }
98
99 /* Otherwise, allocate a new slot in the set for the fd. */
100 uv__pollfds_maybe_resize(loop);
101 pe = &loop->poll_fds[loop->poll_fds_used++];
102 pe->fd = w->fd;
103 pe->events = w->pevents;
104 }
105
106 /* Remove a watcher's fd from our poll fds array. */
uv__pollfds_del(uv_loop_t * loop,int fd)107 static void uv__pollfds_del(uv_loop_t* loop, int fd) {
108 size_t i;
109 assert(!loop->poll_fds_iterating);
110 for (i = 0; i < loop->poll_fds_used;) {
111 if (loop->poll_fds[i].fd == fd) {
112 /* swap to last position and remove */
113 --loop->poll_fds_used;
114 uv__pollfds_swap(loop, i, loop->poll_fds_used);
115 loop->poll_fds[loop->poll_fds_used].fd = -1;
116 loop->poll_fds[loop->poll_fds_used].events = 0;
117 loop->poll_fds[loop->poll_fds_used].revents = 0;
118 /* This method is called with an fd of -1 to purge the invalidated fds,
119 * so we may possibly have multiples to remove.
120 */
121 if (-1 != fd)
122 return;
123 } else {
124 /* We must only increment the loop counter when the fds do not match.
125 * Otherwise, when we are purging an invalidated fd, the value just
126 * swapped here from the previous end of the array will be skipped.
127 */
128 ++i;
129 }
130 }
131 }
132
133
uv__io_poll(uv_loop_t * loop,int timeout)134 void uv__io_poll(uv_loop_t* loop, int timeout) {
135 uv__loop_internal_fields_t* lfields;
136 sigset_t* pset;
137 sigset_t set;
138 uint64_t time_base;
139 uint64_t time_diff;
140 struct uv__queue* q;
141 uv__io_t* w;
142 size_t i;
143 unsigned int nevents;
144 int nfds;
145 int have_signals;
146 struct pollfd* pe;
147 int fd;
148 int user_timeout;
149 int reset_timeout;
150
151 if (loop->nfds == 0) {
152 assert(uv__queue_empty(&loop->watcher_queue));
153 return;
154 }
155
156 lfields = uv__get_internal_fields(loop);
157
158 /* Take queued watchers and add their fds to our poll fds array. */
159 while (!uv__queue_empty(&loop->watcher_queue)) {
160 q = uv__queue_head(&loop->watcher_queue);
161 uv__queue_remove(q);
162 uv__queue_init(q);
163
164 w = uv__queue_data(q, uv__io_t, watcher_queue);
165 assert(w->pevents != 0);
166 assert(w->fd >= 0);
167 assert(w->fd < (int) loop->nwatchers);
168
169 uv__pollfds_add(loop, w);
170
171 w->events = w->pevents;
172 }
173
174 /* Prepare a set of signals to block around poll(), if any. */
175 pset = NULL;
176 if (loop->flags & UV_LOOP_BLOCK_SIGPROF) {
177 pset = &set;
178 sigemptyset(pset);
179 sigaddset(pset, SIGPROF);
180 }
181
182 assert(timeout >= -1);
183 time_base = loop->time;
184
185 if (lfields->flags & UV_METRICS_IDLE_TIME) {
186 reset_timeout = 1;
187 user_timeout = timeout;
188 timeout = 0;
189 } else {
190 reset_timeout = 0;
191 }
192
193 /* Loop calls to poll() and processing of results. If we get some
194 * results from poll() but they turn out not to be interesting to
195 * our caller then we need to loop around and poll() again.
196 */
197 for (;;) {
198 /* Only need to set the provider_entry_time if timeout != 0. The function
199 * will return early if the loop isn't configured with UV_METRICS_IDLE_TIME.
200 */
201 if (timeout != 0)
202 uv__metrics_set_provider_entry_time(loop);
203
204 /* Store the current timeout in a location that's globally accessible so
205 * other locations like uv__work_done() can determine whether the queue
206 * of events in the callback were waiting when poll was called.
207 */
208 lfields->current_timeout = timeout;
209
210 if (pset != NULL)
211 if (pthread_sigmask(SIG_BLOCK, pset, NULL))
212 abort();
213 nfds = poll(loop->poll_fds, (nfds_t)loop->poll_fds_used, timeout);
214 if (pset != NULL)
215 if (pthread_sigmask(SIG_UNBLOCK, pset, NULL))
216 abort();
217
218 /* Update loop->time unconditionally. It's tempting to skip the update when
219 * timeout == 0 (i.e. non-blocking poll) but there is no guarantee that the
220 * operating system didn't reschedule our process while in the syscall.
221 */
222 SAVE_ERRNO(uv__update_time(loop));
223
224 if (nfds == 0) {
225 if (reset_timeout != 0) {
226 timeout = user_timeout;
227 reset_timeout = 0;
228 if (timeout == -1)
229 continue;
230 if (timeout > 0)
231 goto update_timeout;
232 }
233
234 assert(timeout != -1);
235 return;
236 }
237
238 if (nfds == -1) {
239 if (errno != EINTR)
240 abort();
241
242 if (reset_timeout != 0) {
243 timeout = user_timeout;
244 reset_timeout = 0;
245 }
246
247 if (timeout == -1)
248 continue;
249
250 if (timeout == 0)
251 return;
252
253 /* Interrupted by a signal. Update timeout and poll again. */
254 goto update_timeout;
255 }
256
257 /* Tell uv__platform_invalidate_fd not to manipulate our array
258 * while we are iterating over it.
259 */
260 loop->poll_fds_iterating = 1;
261
262 /* Initialize a count of events that we care about. */
263 nevents = 0;
264 have_signals = 0;
265
266 /* Loop over the entire poll fds array looking for returned events. */
267 for (i = 0; i < loop->poll_fds_used; i++) {
268 pe = loop->poll_fds + i;
269 fd = pe->fd;
270
271 /* Skip invalidated events, see uv__platform_invalidate_fd. */
272 if (fd == -1)
273 continue;
274
275 assert(fd >= 0);
276 assert((unsigned) fd < loop->nwatchers);
277
278 w = loop->watchers[fd];
279
280 if (w == NULL) {
281 /* File descriptor that we've stopped watching, ignore. */
282 uv__platform_invalidate_fd(loop, fd);
283 continue;
284 }
285
286 /* Filter out events that user has not requested us to watch
287 * (e.g. POLLNVAL).
288 */
289 pe->revents &= w->pevents | POLLERR | POLLHUP;
290
291 if (pe->revents != 0) {
292 /* Run signal watchers last. */
293 if (w == &loop->signal_io_watcher) {
294 have_signals = 1;
295 } else {
296 uv__metrics_update_idle_time(loop);
297 w->cb(loop, w, pe->revents);
298 }
299
300 nevents++;
301 }
302 }
303
304 uv__metrics_inc_events(loop, nevents);
305 if (reset_timeout != 0) {
306 timeout = user_timeout;
307 reset_timeout = 0;
308 uv__metrics_inc_events_waiting(loop, nevents);
309 }
310
311 if (have_signals != 0) {
312 uv__metrics_update_idle_time(loop);
313 loop->signal_io_watcher.cb(loop, &loop->signal_io_watcher, POLLIN);
314 }
315
316 loop->poll_fds_iterating = 0;
317
318 /* Purge invalidated fds from our poll fds array. */
319 uv__pollfds_del(loop, -1);
320
321 if (have_signals != 0)
322 return; /* Event loop should cycle now so don't poll again. */
323
324 if (nevents != 0)
325 return;
326
327 if (timeout == 0)
328 return;
329
330 if (timeout == -1)
331 continue;
332
333 update_timeout:
334 assert(timeout > 0);
335
336 time_diff = loop->time - time_base;
337 if (time_diff >= (uint64_t) timeout)
338 return;
339
340 timeout -= time_diff;
341 }
342 }
343
344 /* Remove the given fd from our poll fds array because no one
345 * is interested in its events anymore.
346 */
uv__platform_invalidate_fd(uv_loop_t * loop,int fd)347 void uv__platform_invalidate_fd(uv_loop_t* loop, int fd) {
348 size_t i;
349
350 assert(fd >= 0);
351
352 if (loop->poll_fds_iterating) {
353 /* uv__io_poll is currently iterating. Just invalidate fd. */
354 for (i = 0; i < loop->poll_fds_used; i++)
355 if (loop->poll_fds[i].fd == fd) {
356 loop->poll_fds[i].fd = -1;
357 loop->poll_fds[i].events = 0;
358 loop->poll_fds[i].revents = 0;
359 }
360 } else {
361 /* uv__io_poll is not iterating. Delete fd from the set. */
362 uv__pollfds_del(loop, fd);
363 }
364 }
365
366 /* Check whether the given fd is supported by poll(). */
uv__io_check_fd(uv_loop_t * loop,int fd)367 int uv__io_check_fd(uv_loop_t* loop, int fd) {
368 struct pollfd p[1];
369 int rv;
370
371 p[0].fd = fd;
372 p[0].events = POLLIN;
373
374 do
375 rv = poll(p, 1, 0);
376 while (rv == -1 && (errno == EINTR || errno == EAGAIN));
377
378 if (rv == -1)
379 return UV__ERR(errno);
380
381 if (p[0].revents & POLLNVAL)
382 return UV_EINVAL;
383
384 return 0;
385 }
386
