pidfile.c revision 172577 
150472Speter/*-
238738Sbrian * Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
337Srgrimes * 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 172577 2007-10-12 10:38:05Z kib $");
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
44static int _pidfile_remove(struct pidfh *pfh, int freeit);
45
46static int
47pidfile_verify(struct pidfh *pfh)
48{
49	struct stat sb;
50
51	if (pfh == NULL || pfh->pf_fd == -1)
52		return (EDOOFUS);
53	/*
54	 * Check remembered descriptor.
55	 */
56	if (fstat(pfh->pf_fd, &sb) == -1)
57		return (errno);
58	if (sb.st_dev != pfh->pf_dev || sb.st_ino != pfh->pf_ino)
59		return (EDOOFUS);
60	return (0);
61}
62
63static int
64pidfile_read(const char *path, pid_t *pidptr)
65{
66	char buf[16], *endptr;
67	int error, fd, i;
68
69	fd = open(path, O_RDONLY);
70	if (fd == -1)
71		return (errno);
72
73	i = read(fd, buf, sizeof(buf) - 1);
74	error = errno;	/* Remember errno in case close() wants to change it. */
75	close(fd);
76	if (i == -1)
77		return (error);
78	else if (i == 0)
79		return (EAGAIN);
80	buf[i] = '\0';
81
82	*pidptr = strtol(buf, &endptr, 10);
83	if (endptr != &buf[i])
84		return (EINVAL);
85
86	return (0);
87}
88
89struct pidfh *
90pidfile_open(const char *path, mode_t mode, pid_t *pidptr)
91{
92	struct pidfh *pfh;
93	struct stat sb;
94	int error, fd, len, count;
95	struct timespec rqtp;
96
97	pfh = malloc(sizeof(*pfh));
98	if (pfh == NULL)
99		return (NULL);
100
101	if (path == NULL)
102		len = snprintf(pfh->pf_path, sizeof(pfh->pf_path),
103		    "/var/run/%s.pid", getprogname());
104	else
105		len = snprintf(pfh->pf_path, sizeof(pfh->pf_path),
106		    "%s", path);
107	if (len >= (int)sizeof(pfh->pf_path)) {
108		free(pfh);
109		errno = ENAMETOOLONG;
110		return (NULL);
111	}
112
113	/*
114	 * Open the PID file and obtain exclusive lock.
115	 * We truncate PID file here only to remove old PID immediatelly,
116	 * PID file will be truncated again in pidfile_write(), so
117	 * pidfile_write() can be called multiple times.
118	 */
119	fd = flopen(pfh->pf_path,
120	    O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK, mode);
121	if (fd == -1) {
122		count = 0;
123		rqtp.tv_sec = 0;
124		rqtp.tv_nsec = 5000000;
125		if (errno == EWOULDBLOCK && pidptr != NULL) {
126		again:
127			errno = pidfile_read(pfh->pf_path, pidptr);
128			if (errno == 0)
129				errno = EEXIST;
130			else if (errno == EAGAIN) {
131				if (++count <= 3) {
132					nanosleep(&rqtp, 0);
133					goto again;
134				}
135			}
136		}
137		free(pfh);
138		return (NULL);
139	}
140	/*
141	 * Remember file information, so in pidfile_write() we are sure we write
142	 * to the proper descriptor.
143	 */
144	if (fstat(fd, &sb) == -1) {
145		error = errno;
146		unlink(pfh->pf_path);
147		close(fd);
148		free(pfh);
149		errno = error;
150		return (NULL);
151	}
152
153	pfh->pf_fd = fd;
154	pfh->pf_dev = sb.st_dev;
155	pfh->pf_ino = sb.st_ino;
156
157	return (pfh);
158}
159
160int
161pidfile_write(struct pidfh *pfh)
162{
163	char pidstr[16];
164	int error, fd;
165
166	/*
167	 * Check remembered descriptor, so we don't overwrite some other
168	 * file if pidfile was closed and descriptor reused.
169	 */
170	errno = pidfile_verify(pfh);
171	if (errno != 0) {
172		/*
173		 * Don't close descriptor, because we are not sure if it's ours.
174		 */
175		return (-1);
176	}
177	fd = pfh->pf_fd;
178
179	/*
180	 * Truncate PID file, so multiple calls of pidfile_write() are allowed.
181	 */
182	if (ftruncate(fd, 0) == -1) {
183		error = errno;
184		_pidfile_remove(pfh, 0);
185		errno = error;
186		return (-1);
187	}
188
189	snprintf(pidstr, sizeof(pidstr), "%u", getpid());
190	if (pwrite(fd, pidstr, strlen(pidstr), 0) != (ssize_t)strlen(pidstr)) {
191		error = errno;
192		_pidfile_remove(pfh, 0);
193		errno = error;
194		return (-1);
195	}
196
197	return (0);
198}
199
200int
201pidfile_close(struct pidfh *pfh)
202{
203	int error;
204
205	error = pidfile_verify(pfh);
206	if (error != 0) {
207		errno = error;
208		return (-1);
209	}
210
211	if (close(pfh->pf_fd) == -1)
212		error = errno;
213	free(pfh);
214	if (error != 0) {
215		errno = error;
216		return (-1);
217	}
218	return (0);
219}
220
221static int
222_pidfile_remove(struct pidfh *pfh, int freeit)
223{
224	int error;
225
226	error = pidfile_verify(pfh);
227	if (error != 0) {
228		errno = error;
229		return (-1);
230	}
231
232	if (unlink(pfh->pf_path) == -1)
233		error = errno;
234	if (flock(pfh->pf_fd, LOCK_UN) == -1) {
235		if (error == 0)
236			error = errno;
237	}
238	if (close(pfh->pf_fd) == -1) {
239		if (error == 0)
240			error = errno;
241	}
242	if (freeit)
243		free(pfh);
244	else
245		pfh->pf_fd = -1;
246	if (error != 0) {
247		errno = error;
248		return (-1);
249	}
250	return (0);
251}
252
253int
254pidfile_remove(struct pidfh *pfh)
255{
256
257	return (_pidfile_remove(pfh, 1));
258}
259