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