pidfile.c revision 229937
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 229937 2012-01-10 19:53:25Z 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 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 if (errno == EWOULDBLOCK && pidptr != NULL) { 123 count = 20; 124 rqtp.tv_sec = 0; 125 rqtp.tv_nsec = 5000000; 126 for (;;) { 127 errno = pidfile_read(pfh->pf_path, pidptr); 128 if (errno != EAGAIN || --count == 0) 129 break; 130 nanosleep(&rqtp, 0); 131 } 132 if (errno == EAGAIN) 133 *pidptr = -1; 134 if (errno == 0 || errno == EAGAIN) 135 errno = EEXIST; 136 } 137 free(pfh); 138 return (NULL); 139 } 140 141 /* 142 * Prevent the file descriptor from escaping to other 143 * programs via exec(3). 144 */ 145 if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) { 146 error = errno; 147 unlink(pfh->pf_path); 148 close(fd); 149 free(pfh); 150 errno = error; 151 return (NULL); 152 } 153 154 /* 155 * Remember file information, so in pidfile_write() we are sure we write 156 * to the proper descriptor. 157 */ 158 if (fstat(fd, &sb) == -1) { 159 error = errno; 160 unlink(pfh->pf_path); 161 close(fd); 162 free(pfh); 163 errno = error; 164 return (NULL); 165 } 166 167 pfh->pf_fd = fd; 168 pfh->pf_dev = sb.st_dev; 169 pfh->pf_ino = sb.st_ino; 170 171 return (pfh); 172} 173 174int 175pidfile_write(struct pidfh *pfh) 176{ 177 char pidstr[16]; 178 int error, fd; 179 180 /* 181 * Check remembered descriptor, so we don't overwrite some other 182 * file if pidfile was closed and descriptor reused. 183 */ 184 errno = pidfile_verify(pfh); 185 if (errno != 0) { 186 /* 187 * Don't close descriptor, because we are not sure if it's ours. 188 */ 189 return (-1); 190 } 191 fd = pfh->pf_fd; 192 193 /* 194 * Truncate PID file, so multiple calls of pidfile_write() are allowed. 195 */ 196 if (ftruncate(fd, 0) == -1) { 197 error = errno; 198 _pidfile_remove(pfh, 0); 199 errno = error; 200 return (-1); 201 } 202 203 snprintf(pidstr, sizeof(pidstr), "%u", getpid()); 204 if (pwrite(fd, pidstr, strlen(pidstr), 0) != (ssize_t)strlen(pidstr)) { 205 error = errno; 206 _pidfile_remove(pfh, 0); 207 errno = error; 208 return (-1); 209 } 210 211 return (0); 212} 213 214int 215pidfile_close(struct pidfh *pfh) 216{ 217 int error; 218 219 error = pidfile_verify(pfh); 220 if (error != 0) { 221 errno = error; 222 return (-1); 223 } 224 225 if (close(pfh->pf_fd) == -1) 226 error = errno; 227 free(pfh); 228 if (error != 0) { 229 errno = error; 230 return (-1); 231 } 232 return (0); 233} 234 235static int 236_pidfile_remove(struct pidfh *pfh, int freeit) 237{ 238 int error; 239 240 error = pidfile_verify(pfh); 241 if (error != 0) { 242 errno = error; 243 return (-1); 244 } 245 246 if (unlink(pfh->pf_path) == -1) 247 error = errno; 248 if (close(pfh->pf_fd) == -1) { 249 if (error == 0) 250 error = errno; 251 } 252 if (freeit) 253 free(pfh); 254 else 255 pfh->pf_fd = -1; 256 if (error != 0) { 257 errno = error; 258 return (-1); 259 } 260 return (0); 261} 262 263int 264pidfile_remove(struct pidfh *pfh) 265{ 266 267 return (_pidfile_remove(pfh, 1)); 268} 269 270int 271pidfile_fileno(struct pidfh *pfh) 272{ 273 if (pfh == NULL || pfh->pf_fd == -1) { 274 errno = EDOOFUS; 275 return (-1); 276 } 277 return (pfh->pf_fd); 278} 279