libvirt/src/util/virpidfile.c

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/*
* virpidfile.c: manipulation of pidfiles
*
* Copyright (C) 2010-2012 Red Hat, Inc.
* Copyright (C) 2006, 2007 Binary Karma
* Copyright (C) 2006 Shuveb Hussain
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see
* <http://www.gnu.org/licenses/>.
*
*/
#include <config.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/stat.h>
#include "virpidfile.h"
#include "virfile.h"
#include "memory.h"
#include "util.h"
#include "intprops.h"
#include "logging.h"
#include "virterror_internal.h"
#include "c-ctype.h"
#define VIR_FROM_THIS VIR_FROM_NONE
char *virPidFileBuildPath(const char *dir, const char* name)
{
char *pidfile;
if (virAsprintf(&pidfile, "%s/%s.pid", dir, name) < 0)
return NULL;
return pidfile;
}
int virPidFileWritePath(const char *pidfile,
pid_t pid)
{
int rc;
int fd;
char pidstr[INT_BUFSIZE_BOUND(pid)];
if ((fd = open(pidfile,
O_WRONLY | O_CREAT | O_TRUNC,
S_IRUSR | S_IWUSR)) < 0) {
rc = -errno;
goto cleanup;
}
snprintf(pidstr, sizeof(pidstr), "%lld", (long long) pid);
if (safewrite(fd, pidstr, strlen(pidstr)) < 0) {
rc = -errno;
VIR_FORCE_CLOSE(fd);
goto cleanup;
}
rc = 0;
cleanup:
if (VIR_CLOSE(fd) < 0)
rc = -errno;
return rc;
}
int virPidFileWrite(const char *dir,
const char *name,
pid_t pid)
{
int rc;
char *pidfile = NULL;
if (name == NULL || dir == NULL) {
rc = -EINVAL;
goto cleanup;
}
if (virFileMakePath(dir) < 0) {
rc = -errno;
goto cleanup;
}
if (!(pidfile = virPidFileBuildPath(dir, name))) {
rc = -ENOMEM;
goto cleanup;
}
rc = virPidFileWritePath(pidfile, pid);
cleanup:
VIR_FREE(pidfile);
return rc;
}
int virPidFileReadPath(const char *path,
pid_t *pid)
{
int fd;
int rc;
ssize_t bytes;
long long pid_value = 0;
char pidstr[INT_BUFSIZE_BOUND(pid_value)];
char *endptr = NULL;
*pid = 0;
if ((fd = open(path, O_RDONLY)) < 0) {
rc = -errno;
goto cleanup;
}
bytes = saferead(fd, pidstr, sizeof(pidstr));
if (bytes < 0) {
rc = -errno;
VIR_FORCE_CLOSE(fd);
goto cleanup;
}
pidstr[bytes] = '\0';
if (virStrToLong_ll(pidstr, &endptr, 10, &pid_value) < 0 ||
!(*endptr == '\0' || c_isspace(*endptr)) ||
(pid_t) pid_value != pid_value) {
rc = -1;
goto cleanup;
}
*pid = pid_value;
rc = 0;
cleanup:
if (VIR_CLOSE(fd) < 0)
rc = -errno;
return rc;
}
int virPidFileRead(const char *dir,
const char *name,
pid_t *pid)
{
int rc;
char *pidfile = NULL;
*pid = 0;
if (name == NULL || dir == NULL) {
rc = -EINVAL;
goto cleanup;
}
if (!(pidfile = virPidFileBuildPath(dir, name))) {
rc = -ENOMEM;
goto cleanup;
}
rc = virPidFileReadPath(pidfile, pid);
cleanup:
VIR_FREE(pidfile);
return rc;
}
/**
* virPidFileReadPathIfAlive:
* @path: path to pidfile
* @pid: variable to return pid in
* @binpath: path of executable associated with the pidfile
*
* This will attempt to read a pid from @path, and store it
* in @pid. The @pid will only be set, however, if the
* pid in @path is running, and its executable path
* resolves to @binpath. This adds protection against
* recycling of previously reaped pids.
*
* If @binpath is NULL the check for the executable path
* is skipped.
*
* Returns -errno upon error, or zero on successful
* reading of the pidfile. If the PID was not still
* alive, zero will be returned, but @pid will be
* set to -1.
*/
int virPidFileReadPathIfAlive(const char *path,
pid_t *pid,
const char *binpath)
{
int rc;
char *procpath = NULL;
rc = virPidFileReadPath(path, pid);
if (rc < 0)
return rc;
#ifndef WIN32
/* Check that it's still alive. Safe to skip this sanity check on
* mingw, which lacks kill(). */
if (kill(*pid, 0) < 0) {
*pid = -1;
return 0;
}
#endif
if (binpath) {
if (virAsprintf(&procpath, "/proc/%lld/exe", (long long)*pid) < 0) {
*pid = -1;
return -1;
}
if (virFileIsLink(procpath) &&
virFileLinkPointsTo(procpath, binpath) == 0)
*pid = -1;
VIR_FREE(procpath);
}
return 0;
}
/**
* virPidFileReadIfAlive:
* @dir: directory containing pidfile
* @name: base filename of pidfile
* @pid: variable to return pid in
* @binpath: path of executable associated with the pidfile
*
* This will attempt to read a pid from the pidfile @name
* in directory @dir, and store it in @pid. The @pid will
* only be set, however, if the pid in @name is running,
* and its executable path resolves to @binpath. This adds
* protection against recycling of previously reaped pids.
*
* Returns -errno upon error, or zero on successful
* reading of the pidfile. If the PID was not still
* alive, zero will be returned, but @pid will be
* set to -1.
*/
int virPidFileReadIfAlive(const char *dir,
const char *name,
pid_t *pid,
const char *binpath)
{
int rc = 0;
char *pidfile = NULL;
if (name == NULL || dir == NULL) {
rc = -EINVAL;
goto cleanup;
}
if (!(pidfile = virPidFileBuildPath(dir, name))) {
rc = -ENOMEM;
goto cleanup;
}
rc = virPidFileReadPathIfAlive(pidfile, pid, binpath);
cleanup:
VIR_FREE(pidfile);
return rc;
}
int virPidFileDeletePath(const char *pidfile)
{
int rc = 0;
if (unlink(pidfile) < 0 && errno != ENOENT)
rc = -errno;
return rc;
}
int virPidFileDelete(const char *dir,
const char *name)
{
int rc = 0;
char *pidfile = NULL;
if (name == NULL || dir == NULL) {
rc = -EINVAL;
goto cleanup;
}
if (!(pidfile = virPidFileBuildPath(dir, name))) {
rc = -ENOMEM;
goto cleanup;
}
rc = virPidFileDeletePath(pidfile);
cleanup:
VIR_FREE(pidfile);
return rc;
}
int virPidFileAcquirePath(const char *path,
pid_t pid)
{
int fd = -1;
char pidstr[INT_BUFSIZE_BOUND(pid)];
if (path[0] == '\0')
return 0;
while (1) {
struct stat a, b;
if ((fd = open(path, O_WRONLY|O_CREAT, 0644)) < 0) {
virReportSystemError(errno,
_("Failed to open pid file '%s'"),
path);
return -1;
}
if (virSetCloseExec(fd) < 0) {
virReportSystemError(errno,
_("Failed to set close-on-exec flag '%s'"),
path);
VIR_FORCE_CLOSE(fd);
return -1;
}
if (fstat(fd, &b) < 0) {
virReportSystemError(errno,
_("Unable to check status of pid file '%s'"),
path);
VIR_FORCE_CLOSE(fd);
return -1;
}
if (virFileLock(fd, false, 0, 1) < 0) {
virReportSystemError(errno,
_("Failed to acquire pid file '%s'"),
path);
VIR_FORCE_CLOSE(fd);
return -1;
}
/* Now make sure the pidfile we locked is the same
* one that now exists on the filesystem
*/
if (stat(path, &a) < 0) {
char ebuf[1024] ATTRIBUTE_UNUSED;
VIR_DEBUG("Pid file '%s' disappeared: %s",
path, virStrerror(errno, ebuf, sizeof(ebuf)));
VIR_FORCE_CLOSE(fd);
2012-10-11 16:31:20 +00:00
/* Someone else must be racing with us, so try again */
continue;
}
if (a.st_ino == b.st_ino)
break;
VIR_DEBUG("Pid file '%s' was recreated", path);
VIR_FORCE_CLOSE(fd);
2012-10-11 16:31:20 +00:00
/* Someone else must be racing with us, so try again */
}
snprintf(pidstr, sizeof(pidstr), "%lld", (long long) pid);
if (safewrite(fd, pidstr, strlen(pidstr)) < 0) {
virReportSystemError(errno,
_("Failed to write to pid file '%s'"),
path);
VIR_FORCE_CLOSE(fd);
}
return fd;
}
int virPidFileAcquire(const char *dir,
const char *name,
pid_t pid)
{
int rc = 0;
char *pidfile = NULL;
if (name == NULL || dir == NULL) {
rc = -EINVAL;
goto cleanup;
}
if (!(pidfile = virPidFileBuildPath(dir, name))) {
rc = -ENOMEM;
goto cleanup;
}
rc = virPidFileAcquirePath(pidfile, pid);
cleanup:
VIR_FREE(pidfile);
return rc;
}
int virPidFileReleasePath(const char *path,
int fd)
{
int rc = 0;
/*
* We need to unlink before closing the FD to avoid
* a race, but Win32 won't let you unlink an open
* file handle. So on that platform we do the reverse
* and just have to live with the possible race.
*/
#ifdef WIN32
VIR_FORCE_CLOSE(fd);
if (unlink(path) < 0 && errno != ENOENT)
rc = -errno;
#else
if (unlink(path) < 0 && errno != ENOENT)
rc = -errno;
VIR_FORCE_CLOSE(fd);
#endif
return rc;
}
int virPidFileRelease(const char *dir,
const char *name,
int fd)
{
int rc = 0;
char *pidfile = NULL;
if (name == NULL || dir == NULL) {
rc = -EINVAL;
goto cleanup;
}
if (!(pidfile = virPidFileBuildPath(dir, name))) {
rc = -ENOMEM;
goto cleanup;
}
rc = virPidFileReleasePath(pidfile, fd);
cleanup:
VIR_FREE(pidfile);
return rc;
}