Index: head/lib/libutil/pidfile.3 =================================================================== --- head/lib/libutil/pidfile.3 (revision 172576) +++ head/lib/libutil/pidfile.3 (revision 172577) @@ -1,249 +1,253 @@ .\" Copyright (c) 2005 Pawel Jakub Dawidek .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" $FreeBSD$ .\" .Dd August 22, 2005 .Dt PIDFILE 3 .Os .Sh NAME .Nm pidfile_open , .Nm pidfile_write , .Nm pidfile_close , .Nm pidfile_remove .Nd "library for PID files handling" .Sh LIBRARY .Lb libutil .Sh SYNOPSIS .In sys/param.h .In libutil.h .Ft "struct pidfh *" .Fn pidfile_open "const char *path" "mode_t mode" "pid_t *pidptr" .Ft int .Fn pidfile_write "struct pidfh *pfh" .Ft int .Fn pidfile_close "struct pidfh *pfh" .Ft int .Fn pidfile_remove "struct pidfh *pfh" .Sh DESCRIPTION The .Nm pidfile family of functions allows daemons to handle PID files. It uses .Xr flock 2 to lock a pidfile and detect already running daemons. .Pp The .Fn pidfile_open function opens (or creates) a file specified by the .Fa path argument and locks it with the .Xr flock 2 system call. If a file can not be locked, a PID of an already running daemon is returned in the .Fa pidptr argument (if it is not .Dv NULL ) . The function does not write process' PID into the file here, so it can be used before .Fn fork Ns ing and exit with a proper error message when needed. If the .Fa path argument is .Dv NULL , .Pa /var/run/ Ns Ao Va progname Ac Ns Pa .pid file will be used. .Pp The .Fn pidfile_write function writes process' PID into a previously opened file. .Pp The .Fn pidfile_close function closes a pidfile. It should be used after daemon .Fn fork Ns s to start a child process. .Pp The .Fn pidfile_remove function closes and removes a pidfile. .Sh RETURN VALUES The .Fn pidfile_open function returns a valid pointer to a .Vt pidfh structure on success, or .Dv NULL if an error occurs. If an error occurs, .Va errno will be set. .Rv -std pidfile_write pidfile_close pidfile_remove .Sh EXAMPLES The following example shows in which order these functions should be used. Note that it is safe to pass .Dv NULL to .Fn pidfile_write , .Fn pidfile_remove and .Fn pidfile_close functions. .Bd -literal struct pidfh *pfh; pid_t otherpid, childpid; pfh = pidfile_open("/var/run/daemon.pid", 0600, &otherpid); if (pfh == NULL) { if (errno == EEXIST) { errx(EXIT_FAILURE, "Daemon already running, pid: %jd.", (intmax_t)otherpid); } /* If we cannot create pidfile from other reasons, only warn. */ warn("Cannot open or create pidfile"); } if (daemon(0, 0) == -1) { warn("Cannot daemonize"); pidfile_remove(pfh); exit(EXIT_FAILURE); } pidfile_write(pfh); for (;;) { /* Do work. */ childpid = fork(); switch (childpid) { case -1: syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno)); break; case 0: pidfile_close(pfh); /* Do child work. */ break; default: syslog(LOG_INFO, "Child %jd started.", (intmax_t)childpid); break; } } pidfile_remove(pfh); exit(EXIT_SUCCESS); .Ed .Sh ERRORS The .Fn pidfile_open function will fail if: .Bl -tag -width Er .It Bq Er EEXIST Some process already holds the lock on the given pidfile, meaning that a daemon is already running. .It Bq Er ENAMETOOLONG Specified pidfile's name is too long. .It Bq Er EINVAL Some process already holds the lock on the given pidfile, but PID read from there is invalid. +.It Bq Er EAGAIN +Some process already holds the lock on the given pidfile, but the file +is truncated. Most likely, the existing daemon is writing new PID into +the file. .El .Pp The .Fn pidfile_open function may also fail and set .Va errno for any errors specified for the .Xr fstat 2 , .Xr open 2 , and .Xr read 2 calls. .Pp The .Fn pidfile_write function will fail if: .Bl -tag -width Er .It Bq Er EDOOFUS Improper function use. Probably called before .Fn pidfile_open . .El .Pp The .Fn pidfile_write function may also fail and set .Va errno for any errors specified for the .Xr fstat 2 , .Xr ftruncate 2 , and .Xr write 2 calls. .Pp The .Fn pidfile_close function may fail and set .Va errno for any errors specified for the .Xr close 2 and .Xr fstat 2 calls. .Pp The .Fn pidfile_remove function will fail if: .Bl -tag -width Er .It Bq Er EDOOFUS Improper function use. Probably called not from the process which made .Fn pidfile_write . .El .Pp The .Fn pidfile_remove function may also fail and set .Va errno for any errors specified for the .Xr close 2 , .Xr flock 2 , .Xr fstat 2 , .Xr write 2 , and .Xr unlink 2 calls. .Sh SEE ALSO .Xr flock 2 , .Xr open 2 , .Xr daemon 3 .Sh AUTHORS .An -nosplit The .Nm pidfile functionality is based on ideas from .An John-Mark Gurney Aq jmg@FreeBSD.org . .Pp The code and manual page was written by .An Pawel Jakub Dawidek Aq pjd@FreeBSD.org . Index: head/lib/libutil/pidfile.c =================================================================== --- head/lib/libutil/pidfile.c (revision 172576) +++ head/lib/libutil/pidfile.c (revision 172577) @@ -1,244 +1,258 @@ /*- * Copyright (c) 2005 Pawel Jakub Dawidek * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include __FBSDID("$FreeBSD$"); #include #include #include #include #include #include #include #include +#include #include #include #include static int _pidfile_remove(struct pidfh *pfh, int freeit); static int pidfile_verify(struct pidfh *pfh) { struct stat sb; if (pfh == NULL || pfh->pf_fd == -1) return (EDOOFUS); /* * Check remembered descriptor. */ if (fstat(pfh->pf_fd, &sb) == -1) return (errno); if (sb.st_dev != pfh->pf_dev || sb.st_ino != pfh->pf_ino) return (EDOOFUS); return (0); } static int pidfile_read(const char *path, pid_t *pidptr) { char buf[16], *endptr; int error, fd, i; fd = open(path, O_RDONLY); if (fd == -1) return (errno); i = read(fd, buf, sizeof(buf) - 1); error = errno; /* Remember errno in case close() wants to change it. */ close(fd); if (i == -1) return (error); + else if (i == 0) + return (EAGAIN); buf[i] = '\0'; *pidptr = strtol(buf, &endptr, 10); if (endptr != &buf[i]) return (EINVAL); return (0); } struct pidfh * pidfile_open(const char *path, mode_t mode, pid_t *pidptr) { struct pidfh *pfh; struct stat sb; - int error, fd, len; + int error, fd, len, count; + struct timespec rqtp; pfh = malloc(sizeof(*pfh)); if (pfh == NULL) return (NULL); if (path == NULL) len = snprintf(pfh->pf_path, sizeof(pfh->pf_path), "/var/run/%s.pid", getprogname()); else len = snprintf(pfh->pf_path, sizeof(pfh->pf_path), "%s", path); if (len >= (int)sizeof(pfh->pf_path)) { free(pfh); errno = ENAMETOOLONG; return (NULL); } /* * Open the PID file and obtain exclusive lock. * We truncate PID file here only to remove old PID immediatelly, * PID file will be truncated again in pidfile_write(), so * pidfile_write() can be called multiple times. */ fd = flopen(pfh->pf_path, O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK, mode); if (fd == -1) { + count = 0; + rqtp.tv_sec = 0; + rqtp.tv_nsec = 5000000; if (errno == EWOULDBLOCK && pidptr != NULL) { + again: errno = pidfile_read(pfh->pf_path, pidptr); if (errno == 0) errno = EEXIST; + else if (errno == EAGAIN) { + if (++count <= 3) { + nanosleep(&rqtp, 0); + goto again; + } + } } free(pfh); return (NULL); } /* * Remember file information, so in pidfile_write() we are sure we write * to the proper descriptor. */ if (fstat(fd, &sb) == -1) { error = errno; unlink(pfh->pf_path); close(fd); free(pfh); errno = error; return (NULL); } pfh->pf_fd = fd; pfh->pf_dev = sb.st_dev; pfh->pf_ino = sb.st_ino; return (pfh); } int pidfile_write(struct pidfh *pfh) { char pidstr[16]; int error, fd; /* * Check remembered descriptor, so we don't overwrite some other * file if pidfile was closed and descriptor reused. */ errno = pidfile_verify(pfh); if (errno != 0) { /* * Don't close descriptor, because we are not sure if it's ours. */ return (-1); } fd = pfh->pf_fd; /* * Truncate PID file, so multiple calls of pidfile_write() are allowed. */ if (ftruncate(fd, 0) == -1) { error = errno; _pidfile_remove(pfh, 0); errno = error; return (-1); } snprintf(pidstr, sizeof(pidstr), "%u", getpid()); if (pwrite(fd, pidstr, strlen(pidstr), 0) != (ssize_t)strlen(pidstr)) { error = errno; _pidfile_remove(pfh, 0); errno = error; return (-1); } return (0); } int pidfile_close(struct pidfh *pfh) { int error; error = pidfile_verify(pfh); if (error != 0) { errno = error; return (-1); } if (close(pfh->pf_fd) == -1) error = errno; free(pfh); if (error != 0) { errno = error; return (-1); } return (0); } static int _pidfile_remove(struct pidfh *pfh, int freeit) { int error; error = pidfile_verify(pfh); if (error != 0) { errno = error; return (-1); } if (unlink(pfh->pf_path) == -1) error = errno; if (flock(pfh->pf_fd, LOCK_UN) == -1) { if (error == 0) error = errno; } if (close(pfh->pf_fd) == -1) { if (error == 0) error = errno; } if (freeit) free(pfh); else pfh->pf_fd = -1; if (error != 0) { errno = error; return (-1); } return (0); } int pidfile_remove(struct pidfh *pfh) { return (_pidfile_remove(pfh, 1)); }