Implement PID tracking for kernel tracing
[lttng-tools.git] / src / common / pipe.c
CommitLineData
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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
6c1c0768 19#define _LGPL_SOURCE
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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 */
31static 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 */
39static 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 */
47static 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 */
55static 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 */
65static 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
84end:
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 */
93static 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
112end:
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 */
122struct 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
159error:
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 */
169int 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 */
188int 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 */
206int 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 */
228void 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 *
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261 * Return "count" on success. Return < count on error. errno can be used
262 * to check the actual error.
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263 */
264ssize_t lttng_pipe_read(struct lttng_pipe *pipe, void *buf, size_t count)
265{
6cd525e8 266 ssize_t ret;
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267
268 assert(pipe);
269 assert(buf);
270
271 lock_read_side(pipe);
9fd92637 272 if (!lttng_pipe_is_read_open(pipe)) {
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273 ret = -1;
274 errno = EBADF;
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275 goto error;
276 }
6cd525e8 277 ret = lttng_read(pipe->fd[0], buf, count);
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278error:
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 *
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286 * Return "count" on success. Return < count on error. errno can be used
287 * to check the actual error.
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288 */
289ssize_t lttng_pipe_write(struct lttng_pipe *pipe, const void *buf,
290 size_t count)
291{
6cd525e8 292 ssize_t ret;
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293
294 assert(pipe);
295 assert(buf);
296
297 lock_write_side(pipe);
9fd92637 298 if (!lttng_pipe_is_write_open(pipe)) {
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299 ret = -1;
300 errno = EBADF;
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301 goto error;
302 }
6cd525e8 303 ret = lttng_write(pipe->fd[1], buf, count);
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304error:
305 unlock_write_side(pipe);
306 return ret;
307}
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