09e905de4fb64f1819a9cf5b3b8cdfc6281c015b
[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 _GNU_SOURCE
19 #define _LGPL_SOURCE
20 #include <assert.h>
21 #include <fcntl.h>
22 #include <unistd.h>
23
24 #include <common/common.h>
25
26 #include "pipe.h"
27
28 /*
29 * Lock read side of a pipe.
30 */
31 static void lock_read_side(struct lttng_pipe *pipe)
32 {
33 pthread_mutex_lock(&pipe->read_mutex);
34 }
35
36 /*
37 * Unlock read side of a pipe.
38 */
39 static void unlock_read_side(struct lttng_pipe *pipe)
40 {
41 pthread_mutex_unlock(&pipe->read_mutex);
42 }
43
44 /*
45 * Lock write side of a pipe.
46 */
47 static void lock_write_side(struct lttng_pipe *pipe)
48 {
49 pthread_mutex_lock(&pipe->write_mutex);
50 }
51
52 /*
53 * Unlock write side of a pipe.
54 */
55 static void unlock_write_side(struct lttng_pipe *pipe)
56 {
57 pthread_mutex_unlock(&pipe->write_mutex);
58 }
59
60 /*
61 * Internal function. Close read side of pipe WITHOUT locking the mutex.
62 *
63 * Return 0 on success else a negative errno from close(2).
64 */
65 static int _pipe_read_close(struct lttng_pipe *pipe)
66 {
67 int ret, ret_val = 0;
68
69 assert(pipe);
70
71 if (!lttng_pipe_is_read_open(pipe)) {
72 goto end;
73 }
74
75 do {
76 ret = close(pipe->fd[0]);
77 } while (ret < 0 && errno == EINTR);
78 if (ret < 0) {
79 PERROR("close lttng read pipe");
80 ret_val = -errno;
81 }
82 pipe->r_state = LTTNG_PIPE_STATE_CLOSED;
83
84 end:
85 return ret_val;
86 }
87
88 /*
89 * Internal function. Close write side of pipe WITHOUT locking the mutex.
90 *
91 * Return 0 on success else a negative errno from close(2).
92 */
93 static int _pipe_write_close(struct lttng_pipe *pipe)
94 {
95 int ret, ret_val = 0;
96
97 assert(pipe);
98
99 if (!lttng_pipe_is_write_open(pipe)) {
100 goto end;
101 }
102
103 do {
104 ret = close(pipe->fd[1]);
105 } while (ret < 0 && errno == EINTR);
106 if (ret < 0) {
107 PERROR("close lttng write pipe");
108 ret_val = -errno;
109 }
110 pipe->w_state = LTTNG_PIPE_STATE_CLOSED;
111
112 end:
113 return ret_val;
114 }
115
116
117 /*
118 * Open a new lttng pipe and set flags using fcntl().
119 *
120 * Return a newly allocated lttng pipe on success or else NULL.
121 */
122 struct lttng_pipe *lttng_pipe_open(int flags)
123 {
124 int ret;
125 struct lttng_pipe *p;
126
127 p = zmalloc(sizeof(*p));
128 if (!p) {
129 PERROR("zmalloc pipe open");
130 goto error;
131 }
132
133 ret = pipe(p->fd);
134 if (ret < 0) {
135 PERROR("lttng pipe");
136 goto error;
137 }
138
139 if (flags) {
140 int i;
141
142 for (i = 0; i < 2; i++) {
143 ret = fcntl(p->fd[i], F_SETFD, flags);
144 if (ret < 0) {
145 PERROR("fcntl lttng pipe %d", flags);
146 goto error;
147 }
148 }
149 }
150
151 pthread_mutex_init(&p->read_mutex, NULL);
152 pthread_mutex_init(&p->write_mutex, NULL);
153 p->r_state = LTTNG_PIPE_STATE_OPENED;
154 p->w_state = LTTNG_PIPE_STATE_OPENED;
155 p->flags = flags;
156
157 return p;
158
159 error:
160 lttng_pipe_destroy(p);
161 return NULL;
162 }
163
164 /*
165 * Close read side of a lttng pipe.
166 *
167 * Return 0 on success else a negative value.
168 */
169 int lttng_pipe_read_close(struct lttng_pipe *pipe)
170 {
171 int ret;
172
173 assert(pipe);
174
175 /* Handle read side first. */
176 lock_read_side(pipe);
177 ret = _pipe_read_close(pipe);
178 unlock_read_side(pipe);
179
180 return ret;
181 }
182
183 /*
184 * Close write side of a lttng pipe.
185 *
186 * Return 0 on success else a negative value.
187 */
188 int lttng_pipe_write_close(struct lttng_pipe *pipe)
189 {
190 int ret;
191
192 assert(pipe);
193
194 lock_write_side(pipe);
195 ret = _pipe_write_close(pipe);
196 unlock_write_side(pipe);
197
198 return ret;
199 }
200
201 /*
202 * Close both read and write side of a lttng pipe.
203 *
204 * Return 0 on success else a negative value.
205 */
206 int lttng_pipe_close(struct lttng_pipe *pipe)
207 {
208 int ret, ret_val = 0;
209
210 assert(pipe);
211
212 ret = lttng_pipe_read_close(pipe);
213 if (ret < 0) {
214 ret_val = ret;
215 }
216
217 ret = lttng_pipe_write_close(pipe);
218 if (ret < 0) {
219 ret_val = ret;
220 }
221
222 return ret_val;
223 }
224
225 /*
226 * Close and destroy a lttng pipe object. Finally, pipe is freed.
227 */
228 void lttng_pipe_destroy(struct lttng_pipe *pipe)
229 {
230 int ret;
231
232 if (!pipe) {
233 return;
234 }
235
236 /*
237 * Destroy should *never* be called with a locked mutex. These must always
238 * succeed so we unlock them after the close pipe below.
239 */
240 ret = pthread_mutex_trylock(&pipe->read_mutex);
241 assert(!ret);
242 ret = pthread_mutex_trylock(&pipe->write_mutex);
243 assert(!ret);
244
245 /* Close pipes WITHOUT trying to lock the pipes. */
246 (void) _pipe_read_close(pipe);
247 (void) _pipe_write_close(pipe);
248
249 unlock_read_side(pipe);
250 unlock_write_side(pipe);
251
252 (void) pthread_mutex_destroy(&pipe->read_mutex);
253 (void) pthread_mutex_destroy(&pipe->write_mutex);
254
255 free(pipe);
256 }
257
258 /*
259 * Read on a lttng pipe and put the data in buf of at least size count.
260 *
261 * Return "count" on success. Return < count on error. errno can be used
262 * to check the actual error.
263 */
264 ssize_t lttng_pipe_read(struct lttng_pipe *pipe, void *buf, size_t count)
265 {
266 ssize_t ret;
267
268 assert(pipe);
269 assert(buf);
270
271 lock_read_side(pipe);
272 if (!lttng_pipe_is_read_open(pipe)) {
273 ret = -1;
274 errno = EBADF;
275 goto error;
276 }
277 ret = lttng_read(pipe->fd[0], buf, count);
278 error:
279 unlock_read_side(pipe);
280 return ret;
281 }
282
283 /*
284 * Write on a lttng pipe using the data in buf and size of count.
285 *
286 * Return "count" on success. Return < count on error. errno can be used
287 * to check the actual error.
288 */
289 ssize_t lttng_pipe_write(struct lttng_pipe *pipe, const void *buf,
290 size_t count)
291 {
292 ssize_t ret;
293
294 assert(pipe);
295 assert(buf);
296
297 lock_write_side(pipe);
298 if (!lttng_pipe_is_write_open(pipe)) {
299 ret = -1;
300 errno = EBADF;
301 goto error;
302 }
303 ret = lttng_write(pipe->fd[1], buf, count);
304 error:
305 unlock_write_side(pipe);
306 return ret;
307 }
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