pidfile.c revision 230037 
1/*-
2 * Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: head/lib/libutil/pidfile.c 230037 2012-01-12 22:49:36Z ghelmer $");
29
30#include <sys/param.h>
31#include <sys/file.h>
32#include <sys/stat.h>
33
34#include <stdio.h>
35#include <stdlib.h>
36#include <unistd.h>
37#include <fcntl.h>
38#include <string.h>
39#include <time.h>
40#include <err.h>
41#include <errno.h>
42#include <libutil.h>
43
44struct pidfh {
45	int	pf_fd;
46	char	pf_path[MAXPATHLEN + 1];
47	dev_t	pf_dev;
48	ino_t	pf_ino;
49};
50
51static int _pidfile_remove(struct pidfh *pfh, int freeit);
52
53static int
54pidfile_verify(const struct pidfh *pfh)
55{
56	struct stat sb;
57
58	if (pfh == NULL || pfh->pf_fd == -1)
59		return (EDOOFUS);
60	/*
61	 * Check remembered descriptor.
62	 */
63	if (fstat(pfh->pf_fd, &sb) == -1)
64		return (errno);
65	if (sb.st_dev != pfh->pf_dev || sb.st_ino != pfh->pf_ino)
66		return (EDOOFUS);
67	return (0);
68}
69
70static int
71pidfile_read(const char *path, pid_t *pidptr)
72{
73	char buf[16], *endptr;
74	int error, fd, i;
75
76	fd = open(path, O_RDONLY);
77	if (fd == -1)
78		return (errno);
79
80	i = read(fd, buf, sizeof(buf) - 1);
81	error = errno;	/* Remember errno in case close() wants to change it. */
82	close(fd);
83	if (i == -1)
84		return (error);
85	else if (i == 0)
86		return (EAGAIN);
87	buf[i] = '\0';
88
89	*pidptr = strtol(buf, &endptr, 10);
90	if (endptr != &buf[i])
91		return (EINVAL);
92
93	return (0);
94}
95
96struct pidfh *
97pidfile_open(const char *path, mode_t mode, pid_t *pidptr)
98{
99	struct pidfh *pfh;
100	struct stat sb;
101	int error, fd, len, count;
102	struct timespec rqtp;
103
104	pfh = malloc(sizeof(*pfh));
105	if (pfh == NULL)
106		return (NULL);
107
108	if (path == NULL)
109		len = snprintf(pfh->pf_path, sizeof(pfh->pf_path),
110		    "/var/run/%s.pid", getprogname());
111	else
112		len = snprintf(pfh->pf_path, sizeof(pfh->pf_path),
113		    "%s", path);
114	if (len >= (int)sizeof(pfh->pf_path)) {
115		free(pfh);
116		errno = ENAMETOOLONG;
117		return (NULL);
118	}
119
120	/*
121	 * Open the PID file and obtain exclusive lock.
122	 * We truncate PID file here only to remove old PID immediatelly,
123	 * PID file will be truncated again in pidfile_write(), so
124	 * pidfile_write() can be called multiple times.
125	 */
126	fd = flopen(pfh->pf_path,
127	    O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_NONBLOCK, mode);
128	if (fd == -1) {
129		if (errno == EWOULDBLOCK && pidptr != NULL) {
130			count = 20;
131			rqtp.tv_sec = 0;
132			rqtp.tv_nsec = 5000000;
133			for (;;) {
134				errno = pidfile_read(pfh->pf_path, pidptr);
135				if (errno != EAGAIN || --count == 0)
136					break;
137				nanosleep(&rqtp, 0);
138			}
139			if (errno == EAGAIN)
140				*pidptr = -1;
141			if (errno == 0 || errno == EAGAIN)
142				errno = EEXIST;
143		}
144		free(pfh);
145		return (NULL);
146	}
147
148	/*
149	 * Remember file information, so in pidfile_write() we are sure we write
150	 * to the proper descriptor.
151	 */
152	if (fstat(fd, &sb) == -1) {
153		error = errno;
154		unlink(pfh->pf_path);
155		close(fd);
156		free(pfh);
157		errno = error;
158		return (NULL);
159	}
160
161	pfh->pf_fd = fd;
162	pfh->pf_dev = sb.st_dev;
163	pfh->pf_ino = sb.st_ino;
164
165	return (pfh);
166}
167
168int
169pidfile_write(struct pidfh *pfh)
170{
171	char pidstr[16];
172	int error, fd;
173
174	/*
175	 * Check remembered descriptor, so we don't overwrite some other
176	 * file if pidfile was closed and descriptor reused.
177	 */
178	errno = pidfile_verify(pfh);
179	if (errno != 0) {
180		/*
181		 * Don't close descriptor, because we are not sure if it's ours.
182		 */
183		return (-1);
184	}
185	fd = pfh->pf_fd;
186
187	/*
188	 * Truncate PID file, so multiple calls of pidfile_write() are allowed.
189	 */
190	if (ftruncate(fd, 0) == -1) {
191		error = errno;
192		_pidfile_remove(pfh, 0);
193		errno = error;
194		return (-1);
195	}
196
197	snprintf(pidstr, sizeof(pidstr), "%u", getpid());
198	if (pwrite(fd, pidstr, strlen(pidstr), 0) != (ssize_t)strlen(pidstr)) {
199		error = errno;
200		_pidfile_remove(pfh, 0);
201		errno = error;
202		return (-1);
203	}
204
205	return (0);
206}
207
208int
209pidfile_close(struct pidfh *pfh)
210{
211	int error;
212
213	error = pidfile_verify(pfh);
214	if (error != 0) {
215		errno = error;
216		return (-1);
217	}
218
219	if (close(pfh->pf_fd) == -1)
220		error = errno;
221	free(pfh);
222	if (error != 0) {
223		errno = error;
224		return (-1);
225	}
226	return (0);
227}
228
229static int
230_pidfile_remove(struct pidfh *pfh, int freeit)
231{
232	int error;
233
234	error = pidfile_verify(pfh);
235	if (error != 0) {
236		errno = error;
237		return (-1);
238	}
239
240	if (unlink(pfh->pf_path) == -1)
241		error = errno;
242	if (close(pfh->pf_fd) == -1) {
243		if (error == 0)
244			error = errno;
245	}
246	if (freeit)
247		free(pfh);
248	else
249		pfh->pf_fd = -1;
250	if (error != 0) {
251		errno = error;
252		return (-1);
253	}
254	return (0);
255}
256
257int
258pidfile_remove(struct pidfh *pfh)
259{
260
261	return (_pidfile_remove(pfh, 1));
262}
263
264int
265pidfile_fileno(const struct pidfh *pfh)
266{
267
268	if (pfh == NULL || pfh->pf_fd == -1) {
269		errno = EDOOFUS;
270		return (-1);
271	}
272	return (pfh->pf_fd);
273}
274