[mirror_ovs.git] / lib / lockfile.c

 /* Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <config.h>

#include "lockfile.h"

#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

#include "coverage.h"
#include "hash.h"
#include "hmap.h"
#include "ovs-thread.h"
#include "timeval.h"
#include "util.h"
#include "vlog.h"

VLOG_DEFINE_THIS_MODULE(lockfile);

COVERAGE_DEFINE(lockfile_lock);
COVERAGE_DEFINE(lockfile_error);
COVERAGE_DEFINE(lockfile_unlock);

struct lockfile {
    struct hmap_node hmap_node;
    char *name;
    dev_t device;
    ino_t inode;
    int fd;
    HANDLE lock_handle;
};

/* Lock table.
 *
 * We have to do this stupid dance because POSIX says that closing *any* file
 * descriptor for a file on which a process holds a lock drops *all* locks on
 * that file.  That means that we can't afford to open a lockfile more than
 * once. */
static struct ovs_mutex lock_table_mutex = OVS_MUTEX_INITIALIZER;
static struct hmap lock_table__ = HMAP_INITIALIZER(&lock_table__);
static struct hmap *const lock_table OVS_GUARDED_BY(lock_table_mutex)
    = &lock_table__;

static void lockfile_unhash(struct lockfile *);
static int lockfile_try_lock(const char *name, pid_t *pidp,
                             struct lockfile **lockfilep)
    OVS_REQUIRES(&lock_table_mutex);
static void lockfile_do_unlock(struct lockfile * lockfile)
    OVS_REQUIRES(&lock_table_mutex);

/* Returns the name of the lockfile that would be created for locking a file
 * named 'filename_'.  The caller is responsible for freeing the returned name,
 * with free(), when it is no longer needed. */
char *
lockfile_name(const char *filename_)
{
    char *filename;
    const char *slash;
    char *lockname;

    /* If 'filename_' is a symlink, base the name of the lockfile on the
     * symlink's target rather than the name of the symlink.  That way, if a
     * file is symlinked, but there is no symlink for its lockfile, then there
     * is only a single lockfile for both the source and the target of the
     * symlink, not one for each. */
    filename = follow_symlinks(filename_);
    slash = strrchr(filename, '/');
    lockname = (slash
                ? xasprintf("%.*s/.%s.~lock~",
                            (int) (slash - filename), filename, slash + 1)
                : xasprintf(".%s.~lock~", filename));
    free(filename);

    return lockname;
}

/* Locks the configuration file against modification by other processes and
 * re-reads it from disk.
 *
 * Returns 0 on success, otherwise a positive errno value.  On success,
 * '*lockfilep' is set to point to a new "struct lockfile *" that may be
 * unlocked with lockfile_unlock().  On failure, '*lockfilep' is set to
 * NULL.  Will not block if the lock cannot be immediately acquired. */
int
lockfile_lock(const char *file, struct lockfile **lockfilep)
{
    /* Only exclusive ("write") locks are supported.  This is not a problem
     * because the Open vSwitch code that currently uses lock files does so in
     * stylized ways such that any number of readers may access a file while it
     * is being written. */
    char *lock_name;
    pid_t pid;
    int error;

    COVERAGE_INC(lockfile_lock);

    lock_name = lockfile_name(file);

    ovs_mutex_lock(&lock_table_mutex);
    error = lockfile_try_lock(lock_name, &pid, lockfilep);
    ovs_mutex_unlock(&lock_table_mutex);

    if (error) {
        COVERAGE_INC(lockfile_error);
        if (error == EACCES) {
            error = EAGAIN;
        }
        if (pid == getpid()) {
            VLOG_WARN("%s: cannot lock file because this process has already "
                      "locked it", lock_name);
        } else if (pid) {
            VLOG_WARN("%s: cannot lock file because it is already locked by "
                      "pid %ld", lock_name, (long int) pid);
        } else {
            VLOG_WARN("%s: failed to lock file: %s",
                      lock_name, ovs_strerror(error));
        }
    }

    free(lock_name);
    return error;
}

/* Unlocks 'lockfile', which must have been created by a call to
 * lockfile_lock(), and frees 'lockfile'. */
void
lockfile_unlock(struct lockfile *lockfile)
{
    if (lockfile) {
        ovs_mutex_lock(&lock_table_mutex);
        lockfile_do_unlock(lockfile);
        ovs_mutex_unlock(&lock_table_mutex);

        COVERAGE_INC(lockfile_unlock);
        free(lockfile->name);
        free(lockfile);
    }
}

/* Marks all the currently locked lockfiles as no longer locked.  It makes
 * sense to call this function after fork(), because a child created by fork()
 * does not hold its parents' locks. */
void
lockfile_postfork(void)
{
    struct lockfile *lockfile;

    ovs_mutex_lock(&lock_table_mutex);
    HMAP_FOR_EACH (lockfile, hmap_node, lock_table) {
        if (lockfile->fd >= 0) {
            VLOG_WARN("%s: child does not inherit lock", lockfile->name);
            lockfile_unhash(lockfile);
        }
    }
    ovs_mutex_unlock(&lock_table_mutex);
}
\f
static uint32_t
lockfile_hash(dev_t device, ino_t inode)
{
    return hash_bytes(&device, sizeof device,
                      hash_bytes(&inode, sizeof inode, 0));
}

static struct lockfile *
lockfile_find(dev_t device, ino_t inode) OVS_REQUIRES(&lock_table_mutex)
{
    struct lockfile *lockfile;

    HMAP_FOR_EACH_WITH_HASH (lockfile, hmap_node,
                             lockfile_hash(device, inode), lock_table) {
        if (lockfile->device == device && lockfile->inode == inode) {
            return lockfile;
        }
    }
    return NULL;
}

static void
lockfile_unhash(struct lockfile *lockfile) OVS_REQUIRES(&lock_table_mutex)
{
    if (lockfile->fd >= 0) {
        close(lockfile->fd);
        lockfile->fd = -1;
        hmap_remove(lock_table, &lockfile->hmap_node);
    }
}

static struct lockfile *
lockfile_register(const char *name, dev_t device, ino_t inode, int fd)
    OVS_REQUIRES(&lock_table_mutex)
{
    struct lockfile *lockfile;

    lockfile = lockfile_find(device, inode);
    if (lockfile) {
        VLOG_ERR("%s: lock file disappeared and reappeared!", name);
        lockfile_unhash(lockfile);
    }

    lockfile = xmalloc(sizeof *lockfile);
    lockfile->name = xstrdup(name);
    lockfile->device = device;
    lockfile->inode = inode;
    lockfile->fd = fd;
    hmap_insert(lock_table, &lockfile->hmap_node,
                lockfile_hash(device, inode));
    return lockfile;
}

#ifdef _WIN32
static void
lockfile_do_unlock(struct lockfile *lockfile)
    OVS_REQUIRES(&lock_table_mutex)
{
    if (lockfile->fd >= 0) {
        OVERLAPPED overl;
        overl.hEvent = 0;
        overl.Offset = 0;
        overl.OffsetHigh = 0;
        UnlockFileEx(lockfile->lock_handle, 0, 1, 0, &overl);

        close(lockfile->fd);
        lockfile->fd = -1;
    }
}

static int
lockfile_try_lock(const char *name, pid_t *pidp, struct lockfile **lockfilep)
    OVS_REQUIRES(&lock_table_mutex)
{
    HANDLE lock_handle;
    BOOL retval;
    OVERLAPPED overl;
    struct lockfile *lockfile;
    int fd;

    *pidp = 0;

    fd = open(name, O_RDWR | O_CREAT, 0600);
    if (fd < 0) {
        VLOG_WARN("%s: failed to open lock file: %s",
                   name, ovs_strerror(errno));
        return errno;
    }

    lock_handle = (HANDLE)_get_osfhandle(fd);
    if (lock_handle < 0) {
        VLOG_WARN("%s: failed to get the file handle: %s",
                   name, ovs_strerror(errno));
        return errno;
    }

    /* Lock the file 'name' for the region that includes just the first
     * byte. */
    overl.hEvent = 0;
    overl.Offset = 0;
    overl.OffsetHigh = 0;
    retval = LockFileEx(lock_handle, LOCKFILE_EXCLUSIVE_LOCK
                        | LOCKFILE_FAIL_IMMEDIATELY, 0, 1, 0, &overl);
    if (!retval) {
        VLOG_DBG("Failed to lock file : %s", ovs_lasterror_to_string());
        *pidp = getpid();
        return EDEADLK;
    }

    lockfile = xmalloc(sizeof *lockfile);
    lockfile->name = xstrdup(name);
    lockfile->fd = fd;
    lockfile->lock_handle = lock_handle;

    *lockfilep = lockfile;
    return 0;
}
#else /* !_WIN32 */
static void
lockfile_do_unlock(struct lockfile *lockfile)
{
    lockfile_unhash(lockfile);
}

static int
lockfile_try_lock(const char *name, pid_t *pidp, struct lockfile **lockfilep)
    OVS_REQUIRES(&lock_table_mutex)
{
    struct flock l;
    struct stat s;
    int error;
    int fd;

    *lockfilep = NULL;
    *pidp = 0;

    /* Check whether we've already got a lock on that file. */
    if (!stat(name, &s)) {
        if (lockfile_find(s.st_dev, s.st_ino)) {
            *pidp = getpid();
            return EDEADLK;
        }
    } else if (errno != ENOENT) {
        VLOG_WARN("%s: failed to stat lock file: %s",
                  name, ovs_strerror(errno));
        return errno;
    }

    /* Open the lock file. */
    fd = open(name, O_RDWR | O_CREAT, 0600);
    if (fd < 0) {
        VLOG_WARN("%s: failed to open lock file: %s",
                  name, ovs_strerror(errno));
        return errno;
    }

    /* Get the inode and device number for the lock table. */
    if (fstat(fd, &s)) {
        VLOG_ERR("%s: failed to fstat lock file: %s",
                 name, ovs_strerror(errno));
        close(fd);
        return errno;
    }

    /* Try to lock the file. */
    memset(&l, 0, sizeof l);
    l.l_type = F_WRLCK;
    l.l_whence = SEEK_SET;
    l.l_start = 0;
    l.l_len = 0;

    error = fcntl(fd, F_SETLK, &l) == -1 ? errno : 0;

    if (!error) {
        *lockfilep = lockfile_register(name, s.st_dev, s.st_ino, fd);
    } else {
        if (!fcntl(fd, F_GETLK, &l) && l.l_type != F_UNLCK) {
            *pidp = l.l_pid;
        }
        close(fd);
    }
    return error;
}
#endif
Commit	Line	Data
f21fa45f	1	/* Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
ac718c9d BP	2	*
	3	* Licensed under the Apache License, Version 2.0 (the "License");
	4	* you may not use this file except in compliance with the License.
	5	* You may obtain a copy of the License at:
	6	*
	7	* http://www.apache.org/licenses/LICENSE-2.0
	8	*
	9	* Unless required by applicable law or agreed to in writing, software
	10	* distributed under the License is distributed on an "AS IS" BASIS,
	11	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	12	* See the License for the specific language governing permissions and
	13	* limitations under the License.
	14	*/
	15
	16	#include <config.h>
	17
	18	#include "lockfile.h"
	19
	20	#include <errno.h>
	21	#include <fcntl.h>
	22	#include <stdlib.h>
	23	#include <string.h>
	24	#include <sys/stat.h>
	25	#include <unistd.h>
	26
	27	#include "coverage.h"
	28	#include "hash.h"
	29	#include "hmap.h"
5947bbe6	30	#include "ovs-thread.h"
ac718c9d BP	31	#include "timeval.h"
ac718c9d BP	32	#include "util.h"
ac718c9d BP	33	#include "vlog.h"
ac718c9d BP	34
d98e6007	35	VLOG_DEFINE_THIS_MODULE(lockfile);
5136ce49	36
d76f09ea	37	COVERAGE_DEFINE(lockfile_lock);
d76f09ea BP	38	COVERAGE_DEFINE(lockfile_error);
	39	COVERAGE_DEFINE(lockfile_unlock);
	40
ac718c9d BP	41	struct lockfile {
	42	struct hmap_node hmap_node;
	43	char *name;
	44	dev_t device;
	45	ino_t inode;
	46	int fd;
f4c340e1	47	HANDLE lock_handle;
ac718c9d BP	48	};
	49
	50	/* Lock table.
	51	*
	52	* We have to do this stupid dance because POSIX says that closing any file
	53	* descriptor for a file on which a process holds a lock drops all locks on
	54	* that file. That means that we can't afford to open a lockfile more than
	55	* once. */
97be1538 EJ	56	static struct ovs_mutex lock_table_mutex = OVS_MUTEX_INITIALIZER;
	57	static struct hmap lock_table__ = HMAP_INITIALIZER(&lock_table__);
	58	static struct hmap *const lock_table OVS_GUARDED_BY(lock_table_mutex)
	59	= &lock_table__;
5947bbe6	60
ac718c9d	61	static void lockfile_unhash(struct lockfile *);
f21fa45f BP	62	static int lockfile_try_lock(const char name, pid_t pidp,
	63	struct lockfile **lockfilep)
	64	OVS_REQUIRES(&lock_table_mutex);
	65	static void lockfile_do_unlock(struct lockfile * lockfile)
	66	OVS_REQUIRES(&lock_table_mutex);
ac718c9d BP	67
ac718c9d BP	68	/* Returns the name of the lockfile that would be created for locking a file
b1fdc5fb BP	69	* named 'filename_'. The caller is responsible for freeing the returned name,
b1fdc5fb BP	70	* with free(), when it is no longer needed. */
ac718c9d	71	char *
b1fdc5fb	72	lockfile_name(const char *filename_)
ac718c9d	73	{
b1fdc5fb BP	74	char *filename;
	75	const char *slash;
	76	char *lockname;
	77
	78	/* If 'filename_' is a symlink, base the name of the lockfile on the
	79	* symlink's target rather than the name of the symlink. That way, if a
	80	* file is symlinked, but there is no symlink for its lockfile, then there
	81	* is only a single lockfile for both the source and the target of the
	82	* symlink, not one for each. */
	83	filename = follow_symlinks(filename_);
	84	slash = strrchr(filename, '/');
	85	lockname = (slash
	86	? xasprintf("%.*s/.%s.~lock~",
	87	(int) (slash - filename), filename, slash + 1)
	88	: xasprintf(".%s.~lock~", filename));
	89	free(filename);
	90
	91	return lockname;
ac718c9d BP	92	}
	93
	94	/* Locks the configuration file against modification by other processes and
	95	* re-reads it from disk.
	96	*
ac718c9d BP	97	* Returns 0 on success, otherwise a positive errno value. On success,
	98	* 'lockfilep' is set to point to a new "struct lockfile " that may be
	99	* unlocked with lockfile_unlock(). On failure, '*lockfilep' is set to
4770e795	100	* NULL. Will not block if the lock cannot be immediately acquired. */
ac718c9d	101	int
4770e795	102	lockfile_lock(const char file, struct lockfile *lockfilep)
ac718c9d BP	103	{
	104	/* Only exclusive ("write") locks are supported. This is not a problem
	105	* because the Open vSwitch code that currently uses lock files does so in
	106	* stylized ways such that any number of readers may access a file while it
	107	* is being written. */
ac718c9d	108	char *lock_name;
45f1a0d9	109	pid_t pid;
ac718c9d BP	110	int error;
	111
	112	COVERAGE_INC(lockfile_lock);
	113
	114	lock_name = lockfile_name(file);
4770e795	115
97be1538	116	ovs_mutex_lock(&lock_table_mutex);
f21fa45f	117	error = lockfile_try_lock(lock_name, &pid, lockfilep);
97be1538	118	ovs_mutex_unlock(&lock_table_mutex);
4770e795 LA	119
4770e795 LA	120	if (error) {
ac718c9d BP	121	COVERAGE_INC(lockfile_error);
	122	if (error == EACCES) {
	123	error = EAGAIN;
	124	}
607bfcb5 BP	125	if (pid == getpid()) {
	126	VLOG_WARN("%s: cannot lock file because this process has already "
	127	"locked it", lock_name);
	128	} else if (pid) {
45f1a0d9 BP	129	VLOG_WARN("%s: cannot lock file because it is already locked by "
	130	"pid %ld", lock_name, (long int) pid);
	131	} else {
	132	VLOG_WARN("%s: failed to lock file: %s",
10a89ef0	133	lock_name, ovs_strerror(error));
45f1a0d9	134	}
ac718c9d BP	135	}
	136
	137	free(lock_name);
	138	return error;
	139	}
	140
	141	/* Unlocks 'lockfile', which must have been created by a call to
	142	* lockfile_lock(), and frees 'lockfile'. */
	143	void
	144	lockfile_unlock(struct lockfile *lockfile)
	145	{
	146	if (lockfile) {
97be1538	147	ovs_mutex_lock(&lock_table_mutex);
f21fa45f	148	lockfile_do_unlock(lockfile);
97be1538	149	ovs_mutex_unlock(&lock_table_mutex);
5947bbe6 BP	150
5947bbe6 BP	151	COVERAGE_INC(lockfile_unlock);
ac718c9d BP	152	free(lockfile->name);
	153	free(lockfile);
	154	}
	155	}
	156
	157	/* Marks all the currently locked lockfiles as no longer locked. It makes
	158	* sense to call this function after fork(), because a child created by fork()
	159	* does not hold its parents' locks. */
	160	void
	161	lockfile_postfork(void)
	162	{
	163	struct lockfile *lockfile;
	164
97be1538 EJ	165	ovs_mutex_lock(&lock_table_mutex);
97be1538 EJ	166	HMAP_FOR_EACH (lockfile, hmap_node, lock_table) {
ac718c9d BP	167	if (lockfile->fd >= 0) {
	168	VLOG_WARN("%s: child does not inherit lock", lockfile->name);
	169	lockfile_unhash(lockfile);
	170	}
	171	}
97be1538	172	ovs_mutex_unlock(&lock_table_mutex);
ac718c9d BP	173	}
	174	\f
	175	static uint32_t
	176	lockfile_hash(dev_t device, ino_t inode)
	177	{
	178	return hash_bytes(&device, sizeof device,
	179	hash_bytes(&inode, sizeof inode, 0));
	180	}
	181
	182	static struct lockfile *
97be1538	183	lockfile_find(dev_t device, ino_t inode) OVS_REQUIRES(&lock_table_mutex)
ac718c9d BP	184	{
	185	struct lockfile *lockfile;
	186
4e8e4213	187	HMAP_FOR_EACH_WITH_HASH (lockfile, hmap_node,
97be1538	188	lockfile_hash(device, inode), lock_table) {
ac718c9d BP	189	if (lockfile->device == device && lockfile->inode == inode) {
	190	return lockfile;
	191	}
	192	}
	193	return NULL;
	194	}
	195
	196	static void
97be1538	197	lockfile_unhash(struct lockfile *lockfile) OVS_REQUIRES(&lock_table_mutex)
ac718c9d BP	198	{
	199	if (lockfile->fd >= 0) {
	200	close(lockfile->fd);
	201	lockfile->fd = -1;
97be1538	202	hmap_remove(lock_table, &lockfile->hmap_node);
ac718c9d BP	203	}
	204	}
	205
	206	static struct lockfile *
	207	lockfile_register(const char *name, dev_t device, ino_t inode, int fd)
97be1538	208	OVS_REQUIRES(&lock_table_mutex)
ac718c9d BP	209	{
	210	struct lockfile *lockfile;
	211
	212	lockfile = lockfile_find(device, inode);
	213	if (lockfile) {
	214	VLOG_ERR("%s: lock file disappeared and reappeared!", name);
	215	lockfile_unhash(lockfile);
	216	}
	217
	218	lockfile = xmalloc(sizeof *lockfile);
	219	lockfile->name = xstrdup(name);
	220	lockfile->device = device;
	221	lockfile->inode = inode;
	222	lockfile->fd = fd;
97be1538	223	hmap_insert(lock_table, &lockfile->hmap_node,
ac718c9d BP	224	lockfile_hash(device, inode));
	225	return lockfile;
	226	}
	227
f4c340e1 GS	228	#ifdef _WIN32
f4c340e1 GS	229	static void
f21fa45f	230	lockfile_do_unlock(struct lockfile *lockfile)
f4c340e1 GS	231	OVS_REQUIRES(&lock_table_mutex)
	232	{
	233	if (lockfile->fd >= 0) {
	234	OVERLAPPED overl;
	235	overl.hEvent = 0;
	236	overl.Offset = 0;
	237	overl.OffsetHigh = 0;
	238	UnlockFileEx(lockfile->lock_handle, 0, 1, 0, &overl);
	239
	240	close(lockfile->fd);
	241	lockfile->fd = -1;
	242	}
	243	}
	244
	245	static int
f21fa45f	246	lockfile_try_lock(const char name, pid_t pidp, struct lockfile **lockfilep)
f4c340e1 GS	247	OVS_REQUIRES(&lock_table_mutex)
	248	{
	249	HANDLE lock_handle;
	250	BOOL retval;
	251	OVERLAPPED overl;
	252	struct lockfile *lockfile;
	253	int fd;
	254
	255	*pidp = 0;
	256
	257	fd = open(name, O_RDWR \| O_CREAT, 0600);
	258	if (fd < 0) {
	259	VLOG_WARN("%s: failed to open lock file: %s",
	260	name, ovs_strerror(errno));
	261	return errno;
	262	}
	263
	264	lock_handle = (HANDLE)_get_osfhandle(fd);
	265	if (lock_handle < 0) {
	266	VLOG_WARN("%s: failed to get the file handle: %s",
	267	name, ovs_strerror(errno));
	268	return errno;
	269	}
	270
	271	/* Lock the file 'name' for the region that includes just the first
	272	* byte. */
	273	overl.hEvent = 0;
	274	overl.Offset = 0;
	275	overl.OffsetHigh = 0;
	276	retval = LockFileEx(lock_handle, LOCKFILE_EXCLUSIVE_LOCK
	277	\| LOCKFILE_FAIL_IMMEDIATELY, 0, 1, 0, &overl);
	278	if (!retval) {
7acb0553 GS	279	VLOG_DBG("Failed to lock file : %s", ovs_lasterror_to_string());
	280	*pidp = getpid();
	281	return EDEADLK;
f4c340e1 GS	282	}
	283
	284	lockfile = xmalloc(sizeof *lockfile);
	285	lockfile->name = xstrdup(name);
	286	lockfile->fd = fd;
	287	lockfile->lock_handle = lock_handle;
	288
	289	*lockfilep = lockfile;
	290	return 0;
	291	}
f21fa45f BP	292	#else /* !_WIN32 */
	293	static void
	294	lockfile_do_unlock(struct lockfile *lockfile)
	295	{
	296	lockfile_unhash(lockfile);
	297	}
f4c340e1	298
ac718c9d	299	static int
f21fa45f	300	lockfile_try_lock(const char name, pid_t pidp, struct lockfile **lockfilep)
97be1538	301	OVS_REQUIRES(&lock_table_mutex)
ac718c9d BP	302	{
	303	struct flock l;
	304	struct stat s;
	305	int error;
	306	int fd;
	307
	308	*lockfilep = NULL;
45f1a0d9	309	*pidp = 0;
ac718c9d	310
77c513a4 BP	311	/* Check whether we've already got a lock on that file. */
	312	if (!stat(name, &s)) {
	313	if (lockfile_find(s.st_dev, s.st_ino)) {
607bfcb5	314	*pidp = getpid();
77c513a4	315	return EDEADLK;
ac718c9d	316	}
77c513a4 BP	317	} else if (errno != ENOENT) {
77c513a4 BP	318	VLOG_WARN("%s: failed to stat lock file: %s",
10a89ef0	319	name, ovs_strerror(errno));
77c513a4 BP	320	return errno;
77c513a4 BP	321	}
ac718c9d	322
77c513a4 BP	323	/* Open the lock file. */
	324	fd = open(name, O_RDWR \| O_CREAT, 0600);
	325	if (fd < 0) {
	326	VLOG_WARN("%s: failed to open lock file: %s",
10a89ef0	327	name, ovs_strerror(errno));
77c513a4	328	return errno;
ac718c9d BP	329	}
	330
	331	/* Get the inode and device number for the lock table. */
	332	if (fstat(fd, &s)) {
10a89ef0 BP	333	VLOG_ERR("%s: failed to fstat lock file: %s",
10a89ef0 BP	334	name, ovs_strerror(errno));
ac718c9d BP	335	close(fd);
	336	return errno;
	337	}
	338
	339	/* Try to lock the file. */
	340	memset(&l, 0, sizeof l);
	341	l.l_type = F_WRLCK;
	342	l.l_whence = SEEK_SET;
	343	l.l_start = 0;
	344	l.l_len = 0;
	345
4770e795	346	error = fcntl(fd, F_SETLK, &l) == -1 ? errno : 0;
ac718c9d BP	347
	348	if (!error) {
	349	*lockfilep = lockfile_register(name, s.st_dev, s.st_ino, fd);
	350	} else {
45f1a0d9 BP	351	if (!fcntl(fd, F_GETLK, &l) && l.l_type != F_UNLCK) {
	352	*pidp = l.l_pid;
	353	}
ac718c9d BP	354	close(fd);
	355	}
	356	return error;
	357	}
f4c340e1	358	#endif