Add named pipe support to the pipe wrapper
[lttng-tools.git] / src / common / pipe.c
1 /*
2 * Copyright (C) 2013 - David Goulet <dgoulet@efficios.com>
3 *
4 * This program is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License, version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
11 * more details.
12 *
13 * You should have received a copy of the GNU General Public License along with
14 * this program; if not, write to the Free Software Foundation, Inc., 51
15 * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
16 */
17
18 #define _LGPL_SOURCE
19 #include <assert.h>
20 #include <fcntl.h>
21 #include <unistd.h>
22 #include <sys/types.h>
23 #include <sys/stat.h>
24
25 #include <common/common.h>
26
27 #include "pipe.h"
28
29 /*
30 * Lock read side of a pipe.
31 */
32 static void lock_read_side(struct lttng_pipe *pipe)
33 {
34 pthread_mutex_lock(&pipe->read_mutex);
35 }
36
37 /*
38 * Unlock read side of a pipe.
39 */
40 static void unlock_read_side(struct lttng_pipe *pipe)
41 {
42 pthread_mutex_unlock(&pipe->read_mutex);
43 }
44
45 /*
46 * Lock write side of a pipe.
47 */
48 static void lock_write_side(struct lttng_pipe *pipe)
49 {
50 pthread_mutex_lock(&pipe->write_mutex);
51 }
52
53 /*
54 * Unlock write side of a pipe.
55 */
56 static void unlock_write_side(struct lttng_pipe *pipe)
57 {
58 pthread_mutex_unlock(&pipe->write_mutex);
59 }
60
61 /*
62 * Internal function. Close read side of pipe WITHOUT locking the mutex.
63 *
64 * Return 0 on success else a negative errno from close(2).
65 */
66 static int _pipe_read_close(struct lttng_pipe *pipe)
67 {
68 int ret, ret_val = 0;
69
70 assert(pipe);
71
72 if (!lttng_pipe_is_read_open(pipe)) {
73 goto end;
74 }
75
76 do {
77 ret = close(pipe->fd[0]);
78 } while (ret < 0 && errno == EINTR);
79 if (ret < 0) {
80 PERROR("close lttng read pipe");
81 ret_val = -errno;
82 }
83 pipe->r_state = LTTNG_PIPE_STATE_CLOSED;
84
85 end:
86 return ret_val;
87 }
88
89 /*
90 * Internal function. Close write side of pipe WITHOUT locking the mutex.
91 *
92 * Return 0 on success else a negative errno from close(2).
93 */
94 static int _pipe_write_close(struct lttng_pipe *pipe)
95 {
96 int ret, ret_val = 0;
97
98 assert(pipe);
99
100 if (!lttng_pipe_is_write_open(pipe)) {
101 goto end;
102 }
103
104 do {
105 ret = close(pipe->fd[1]);
106 } while (ret < 0 && errno == EINTR);
107 if (ret < 0) {
108 PERROR("close lttng write pipe");
109 ret_val = -errno;
110 }
111 pipe->w_state = LTTNG_PIPE_STATE_CLOSED;
112
113 end:
114 return ret_val;
115 }
116
117 static struct lttng_pipe *_pipe_create(void)
118 {
119 int ret;
120 struct lttng_pipe *p;
121
122 p = zmalloc(sizeof(*p));
123 if (!p) {
124 PERROR("zmalloc pipe create");
125 goto end;
126 }
127 p->fd[0] = p->fd[1] = -1;
128
129 ret = pthread_mutex_init(&p->read_mutex, NULL);
130 if (ret) {
131 PERROR("pthread_mutex_init read lock pipe create");
132 goto error_destroy;
133 }
134 ret = pthread_mutex_init(&p->write_mutex, NULL);
135 if (ret) {
136 PERROR("pthread_mutex_init write lock pipe create");
137 goto error_destroy_rmutex;
138 }
139 end:
140 return p;
141 error_destroy_rmutex:
142 (void) pthread_mutex_destroy(&p->read_mutex);
143 error_destroy:
144 free(p);
145 return NULL;
146 }
147
148 static int _pipe_set_flags(struct lttng_pipe *pipe, int flags)
149 {
150 int i, ret = 0;
151
152 if (!flags) {
153 goto end;
154 }
155
156 for (i = 0; i < 2; i++) {
157 ret = fcntl(pipe->fd[i], F_SETFD, flags);
158 if (ret < 0) {
159 PERROR("fcntl lttng pipe %d", flags);
160 goto end;
161 }
162 }
163 end:
164 return ret;
165 }
166
167 /*
168 * Open a new lttng pipe and set flags using fcntl().
169 *
170 * Return a newly allocated lttng pipe on success or else NULL.
171 */
172 LTTNG_HIDDEN
173 struct lttng_pipe *lttng_pipe_open(int flags)
174 {
175 int ret;
176 struct lttng_pipe *p;
177
178 p = _pipe_create();
179 if (!p) {
180 goto error;
181 }
182
183 ret = pipe(p->fd);
184 if (ret < 0) {
185 PERROR("lttng pipe");
186 goto error;
187 }
188 p->r_state = LTTNG_PIPE_STATE_OPENED;
189 p->w_state = LTTNG_PIPE_STATE_OPENED;
190
191 ret = _pipe_set_flags(p, flags);
192 if (ret) {
193 goto error;
194 }
195
196 p->flags = flags;
197
198 return p;
199 error:
200 lttng_pipe_destroy(p);
201 return NULL;
202 }
203
204 /*
205 * Open a new lttng pipe at path and set flags using fcntl().
206 *
207 * Return a newly allocated lttng pipe on success or else NULL.
208 */
209 LTTNG_HIDDEN
210 struct lttng_pipe *lttng_pipe_named_open(const char *path, mode_t mode,
211 int flags)
212 {
213 int ret, fd_r, fd_w;
214 struct lttng_pipe *pipe;
215
216 pipe = _pipe_create();
217 if (!pipe) {
218 goto error;
219 }
220
221 ret = mkfifo(path, mode);
222 if (ret) {
223 PERROR("mkfifo");
224 goto error;
225 }
226
227 fd_r = open(path, O_RDONLY | O_NONBLOCK);
228 if (fd_r < 0) {
229 PERROR("open fifo");
230 ret = fd_r;
231 goto error;
232 }
233 pipe->fd[0] = fd_r;
234 pipe->r_state = LTTNG_PIPE_STATE_OPENED;
235
236 fd_w = open(path, O_WRONLY | O_NONBLOCK);
237 if (fd_w < 0) {
238 PERROR("open fifo");
239 ret = fd_w;
240 goto error;
241 }
242 pipe->fd[1] = fd_w;
243 pipe->w_state = LTTNG_PIPE_STATE_OPENED;
244
245 ret = _pipe_set_flags(pipe, flags);
246 if (ret) {
247 goto error;
248 }
249 pipe->flags = flags;
250
251 return pipe;
252 error:
253 lttng_pipe_destroy(pipe);
254 return NULL;
255 }
256
257 /*
258 * Close read side of a lttng pipe.
259 *
260 * Return 0 on success else a negative value.
261 */
262 LTTNG_HIDDEN
263 int lttng_pipe_read_close(struct lttng_pipe *pipe)
264 {
265 int ret;
266
267 assert(pipe);
268
269 /* Handle read side first. */
270 lock_read_side(pipe);
271 ret = _pipe_read_close(pipe);
272 unlock_read_side(pipe);
273
274 return ret;
275 }
276
277 /*
278 * Close write side of a lttng pipe.
279 *
280 * Return 0 on success else a negative value.
281 */
282 LTTNG_HIDDEN
283 int lttng_pipe_write_close(struct lttng_pipe *pipe)
284 {
285 int ret;
286
287 assert(pipe);
288
289 lock_write_side(pipe);
290 ret = _pipe_write_close(pipe);
291 unlock_write_side(pipe);
292
293 return ret;
294 }
295
296 /*
297 * Close both read and write side of a lttng pipe.
298 *
299 * Return 0 on success else a negative value.
300 */
301 LTTNG_HIDDEN
302 int lttng_pipe_close(struct lttng_pipe *pipe)
303 {
304 int ret, ret_val = 0;
305
306 assert(pipe);
307
308 ret = lttng_pipe_read_close(pipe);
309 if (ret < 0) {
310 ret_val = ret;
311 }
312
313 ret = lttng_pipe_write_close(pipe);
314 if (ret < 0) {
315 ret_val = ret;
316 }
317
318 return ret_val;
319 }
320
321 /*
322 * Close and destroy a lttng pipe object. Finally, pipe is freed.
323 */
324 LTTNG_HIDDEN
325 void lttng_pipe_destroy(struct lttng_pipe *pipe)
326 {
327 int ret;
328
329 if (!pipe) {
330 return;
331 }
332
333 /*
334 * Destroy should *never* be called with a locked mutex. These must always
335 * succeed so we unlock them after the close pipe below.
336 */
337 ret = pthread_mutex_trylock(&pipe->read_mutex);
338 assert(!ret);
339 ret = pthread_mutex_trylock(&pipe->write_mutex);
340 assert(!ret);
341
342 /* Close pipes WITHOUT trying to lock the pipes. */
343 (void) _pipe_read_close(pipe);
344 (void) _pipe_write_close(pipe);
345
346 unlock_read_side(pipe);
347 unlock_write_side(pipe);
348
349 (void) pthread_mutex_destroy(&pipe->read_mutex);
350 (void) pthread_mutex_destroy(&pipe->write_mutex);
351
352 free(pipe);
353 }
354
355 /*
356 * Read on a lttng pipe and put the data in buf of at least size count.
357 *
358 * Return "count" on success. Return < count on error. errno can be used
359 * to check the actual error.
360 */
361 LTTNG_HIDDEN
362 ssize_t lttng_pipe_read(struct lttng_pipe *pipe, void *buf, size_t count)
363 {
364 ssize_t ret;
365
366 assert(pipe);
367 assert(buf);
368
369 lock_read_side(pipe);
370 if (!lttng_pipe_is_read_open(pipe)) {
371 ret = -1;
372 errno = EBADF;
373 goto error;
374 }
375 ret = lttng_read(pipe->fd[0], buf, count);
376 error:
377 unlock_read_side(pipe);
378 return ret;
379 }
380
381 /*
382 * Write on a lttng pipe using the data in buf and size of count.
383 *
384 * Return "count" on success. Return < count on error. errno can be used
385 * to check the actual error.
386 */
387 LTTNG_HIDDEN
388 ssize_t lttng_pipe_write(struct lttng_pipe *pipe, const void *buf,
389 size_t count)
390 {
391 ssize_t ret;
392
393 assert(pipe);
394 assert(buf);
395
396 lock_write_side(pipe);
397 if (!lttng_pipe_is_write_open(pipe)) {
398 ret = -1;
399 errno = EBADF;
400 goto error;
401 }
402 ret = lttng_write(pipe->fd[1], buf, count);
403 error:
404 unlock_write_side(pipe);
405 return ret;
406 }
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