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 sigset_t* pset;
136 sigset_t set;
137 uint64_t time_base;
138 uint64_t time_diff;
139 QUEUE* q;
140 uv__io_t* w;
141 size_t i;
142 unsigned int nevents;
143 int nfds;
144 int have_signals;
145 struct pollfd* pe;
146 int fd;
147 int user_timeout;
148 int reset_timeout;
149
150 if (loop->nfds == 0) {
151 assert(QUEUE_EMPTY(&loop->watcher_queue));
152 return;
153 }
154
155 /* Take queued watchers and add their fds to our poll fds array. */
156 while (!QUEUE_EMPTY(&loop->watcher_queue)) {
157 q = QUEUE_HEAD(&loop->watcher_queue);
158 QUEUE_REMOVE(q);
159 QUEUE_INIT(q);
160
161 w = QUEUE_DATA(q, uv__io_t, watcher_queue);
162 assert(w->pevents != 0);
163 assert(w->fd >= 0);
164 assert(w->fd < (int) loop->nwatchers);
165
166 uv__pollfds_add(loop, w);
167
168 w->events = w->pevents;
169 }
170
171 /* Prepare a set of signals to block around poll(), if any. */
172 pset = NULL;
173 if (loop->flags & UV_LOOP_BLOCK_SIGPROF) {
174 pset = &set;
175 sigemptyset(pset);
176 sigaddset(pset, SIGPROF);
177 }
178
179 assert(timeout >= -1);
180 time_base = loop->time;
181
182 if (uv__get_internal_fields(loop)->flags & UV_METRICS_IDLE_TIME) {
183 reset_timeout = 1;
184 user_timeout = timeout;
185 timeout = 0;
186 } else {
187 reset_timeout = 0;
188 }
189
190 /* Loop calls to poll() and processing of results. If we get some
191 * results from poll() but they turn out not to be interesting to
192 * our caller then we need to loop around and poll() again.
193 */
194 for (;;) {
195 /* Only need to set the provider_entry_time if timeout != 0. The function
196 * will return early if the loop isn't configured with UV_METRICS_IDLE_TIME.
197 */
198 if (timeout != 0)
199 uv__metrics_set_provider_entry_time(loop);
200
201 if (pset != NULL)
202 if (pthread_sigmask(SIG_BLOCK, pset, NULL))
203 abort();
204 nfds = poll(loop->poll_fds, (nfds_t)loop->poll_fds_used, timeout);
205 if (pset != NULL)
206 if (pthread_sigmask(SIG_UNBLOCK, pset, NULL))
207 abort();
208
209 /* Update loop->time unconditionally. It's tempting to skip the update when
210 * timeout == 0 (i.e. non-blocking poll) but there is no guarantee that the
211 * operating system didn't reschedule our process while in the syscall.
212 */
213 SAVE_ERRNO(uv__update_time(loop));
214
215 if (nfds == 0) {
216 if (reset_timeout != 0) {
217 timeout = user_timeout;
218 reset_timeout = 0;
219 if (timeout == -1)
220 continue;
221 if (timeout > 0)
222 goto update_timeout;
223 }
224
225 assert(timeout != -1);
226 return;
227 }
228
229 if (nfds == -1) {
230 if (errno != EINTR)
231 abort();
232
233 if (reset_timeout != 0) {
234 timeout = user_timeout;
235 reset_timeout = 0;
236 }
237
238 if (timeout == -1)
239 continue;
240
241 if (timeout == 0)
242 return;
243
244 /* Interrupted by a signal. Update timeout and poll again. */
245 goto update_timeout;
246 }
247
248 /* Tell uv__platform_invalidate_fd not to manipulate our array
249 * while we are iterating over it.
250 */
251 loop->poll_fds_iterating = 1;
252
253 /* Initialize a count of events that we care about. */
254 nevents = 0;
255 have_signals = 0;
256
257 /* Loop over the entire poll fds array looking for returned events. */
258 for (i = 0; i < loop->poll_fds_used; i++) {
259 pe = loop->poll_fds + i;
260 fd = pe->fd;
261
262 /* Skip invalidated events, see uv__platform_invalidate_fd. */
263 if (fd == -1)
264 continue;
265
266 assert(fd >= 0);
267 assert((unsigned) fd < loop->nwatchers);
268
269 w = loop->watchers[fd];
270
271 if (w == NULL) {
272 /* File descriptor that we've stopped watching, ignore. */
273 uv__platform_invalidate_fd(loop, fd);
274 continue;
275 }
276
277 /* Filter out events that user has not requested us to watch
278 * (e.g. POLLNVAL).
279 */
280 pe->revents &= w->pevents | POLLERR | POLLHUP;
281
282 if (pe->revents != 0) {
283 /* Run signal watchers last. */
284 if (w == &loop->signal_io_watcher) {
285 have_signals = 1;
286 } else {
287 uv__metrics_update_idle_time(loop);
288 w->cb(loop, w, pe->revents);
289 }
290
291 nevents++;
292 }
293 }
294
295 if (reset_timeout != 0) {
296 timeout = user_timeout;
297 reset_timeout = 0;
298 }
299
300 if (have_signals != 0) {
301 uv__metrics_update_idle_time(loop);
302 loop->signal_io_watcher.cb(loop, &loop->signal_io_watcher, POLLIN);
303 }
304
305 loop->poll_fds_iterating = 0;
306
307 /* Purge invalidated fds from our poll fds array. */
308 uv__pollfds_del(loop, -1);
309
310 if (have_signals != 0)
311 return; /* Event loop should cycle now so don't poll again. */
312
313 if (nevents != 0)
314 return;
315
316 if (timeout == 0)
317 return;
318
319 if (timeout == -1)
320 continue;
321
322 update_timeout:
323 assert(timeout > 0);
324
325 time_diff = loop->time - time_base;
326 if (time_diff >= (uint64_t) timeout)
327 return;
328
329 timeout -= time_diff;
330 }
331 }
332
333 /* Remove the given fd from our poll fds array because no one
334 * is interested in its events anymore.
335 */
uv__platform_invalidate_fd(uv_loop_t * loop,int fd)336 void uv__platform_invalidate_fd(uv_loop_t* loop, int fd) {
337 size_t i;
338
339 assert(fd >= 0);
340
341 if (loop->poll_fds_iterating) {
342 /* uv__io_poll is currently iterating. Just invalidate fd. */
343 for (i = 0; i < loop->poll_fds_used; i++)
344 if (loop->poll_fds[i].fd == fd) {
345 loop->poll_fds[i].fd = -1;
346 loop->poll_fds[i].events = 0;
347 loop->poll_fds[i].revents = 0;
348 }
349 } else {
350 /* uv__io_poll is not iterating. Delete fd from the set. */
351 uv__pollfds_del(loop, fd);
352 }
353 }
354
355 /* Check whether the given fd is supported by poll(). */
uv__io_check_fd(uv_loop_t * loop,int fd)356 int uv__io_check_fd(uv_loop_t* loop, int fd) {
357 struct pollfd p[1];
358 int rv;
359
360 p[0].fd = fd;
361 p[0].events = POLLIN;
362
363 do
364 rv = poll(p, 1, 0);
365 while (rv == -1 && (errno == EINTR || errno == EAGAIN));
366
367 if (rv == -1)
368 return UV__ERR(errno);
369
370 if (p[0].revents & POLLNVAL)
371 return UV_EINVAL;
372
373 return 0;
374 }
375