- /* Copyright (c) 2008, 2009, 2010 Nicira Networks
+ /* Copyright (c) 2008, 2009, 2010, 2011, 2012 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
static struct hmap lock_table = HMAP_INITIALIZER(&lock_table);
static void lockfile_unhash(struct lockfile *);
-static int lockfile_try_lock(const char *name, bool block,
- struct lockfile **lockfilep);
+static int lockfile_try_lock(const char *name, struct lockfile **lockfilep);
/* Returns the name of the lockfile that would be created for locking a file
- * named 'file_name'. The caller is responsible for freeing the returned
- * name, with free(), when it is no longer needed. */
+ * named 'filename_'. The caller is responsible for freeing the returned name,
+ * with free(), when it is no longer needed. */
char *
-lockfile_name(const char *file_name)
+lockfile_name(const char *filename_)
{
- const char *slash = strrchr(file_name, '/');
- return (slash
- ? xasprintf("%.*s/.%s.~lock~",
- (int) (slash - file_name), file_name, slash + 1)
- : xasprintf(".%s.~lock~", file_name));
+ 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.
*
- * The 'timeout' specifies the maximum number of milliseconds to wait for the
- * config file to become free. Use 0 to avoid waiting or INT_MAX to wait
- * forever.
- *
* 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. */
+ * NULL. Will not block if the lock cannot be immediately acquired. */
int
-lockfile_lock(const char *file, int timeout, struct lockfile **lockfilep)
+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. */
- long long int warn_elapsed = 1000;
- long long int start, elapsed;
char *lock_name;
int error;
COVERAGE_INC(lockfile_lock);
lock_name = lockfile_name(file);
- time_refresh();
- start = time_msec();
-
- do {
- error = lockfile_try_lock(lock_name, timeout > 0, lockfilep);
- time_refresh();
- elapsed = time_msec() - start;
- if (elapsed > warn_elapsed) {
- warn_elapsed *= 2;
- VLOG_WARN("%s: waiting for lock file, %lld ms elapsed",
- lock_name, elapsed);
- }
- } while (error == EINTR && (timeout == INT_MAX || elapsed < timeout));
- if (!error) {
- if (elapsed) {
- VLOG_WARN("%s: waited %lld ms for lock file",
- lock_name, elapsed);
- }
- } else if (error == EINTR) {
- COVERAGE_INC(lockfile_timeout);
- VLOG_WARN("%s: giving up on lock file after %lld ms",
- lock_name, elapsed);
- error = ETIMEDOUT;
- } else {
+ error = lockfile_try_lock(lock_name, lockfilep);
+
+ if (error) {
COVERAGE_INC(lockfile_error);
if (error == EACCES) {
error = EAGAIN;
}
- VLOG_WARN("%s: failed to lock file "
- "(after %lld ms, with %d-ms timeout): %s",
- lock_name, elapsed, timeout, strerror(error));
+ VLOG_WARN("%s: failed to lock file: %s",
+ lock_name, strerror(error));
}
free(lock_name);
}
static int
-lockfile_try_lock(const char *name, bool block, struct lockfile **lockfilep)
+lockfile_try_lock(const char *name, struct lockfile **lockfilep)
{
struct flock l;
struct stat s;
*lockfilep = NULL;
- /* Open the lock file, first creating it if necessary. */
- for (;;) {
- /* Check whether we've already got a lock on that file. */
- if (!stat(name, &s)) {
- if (lockfile_find(s.st_dev, s.st_ino)) {
- return EDEADLK;
- }
- } else if (errno != ENOENT) {
- VLOG_WARN("%s: failed to stat lock file: %s",
- name, strerror(errno));
- return errno;
- }
-
- /* Try to open an existing lock file. */
- fd = open(name, O_RDWR);
- if (fd >= 0) {
- break;
- } else if (errno != ENOENT) {
- VLOG_WARN("%s: failed to open lock file: %s",
- name, strerror(errno));
- return errno;
- }
-
- /* Try to create a new lock file. */
- VLOG_INFO("%s: lock file does not exist, creating", name);
- fd = open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
- if (fd >= 0) {
- break;
- } else if (errno != EEXIST) {
- VLOG_WARN("%s: failed to create lock file: %s",
- name, strerror(errno));
- return errno;
+ /* Check whether we've already got a lock on that file. */
+ if (!stat(name, &s)) {
+ if (lockfile_find(s.st_dev, s.st_ino)) {
+ return EDEADLK;
}
+ } else if (errno != ENOENT) {
+ VLOG_WARN("%s: failed to stat lock file: %s",
+ name, strerror(errno));
+ return errno;
+ }
- /* Someone else created the lock file. Try again. */
+ /* 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, strerror(errno));
+ return errno;
}
/* Get the inode and device number for the lock table. */
l.l_len = 0;
time_disable_restart();
- error = fcntl(fd, block ? F_SETLKW : F_SETLK, &l) == -1 ? errno : 0;
+ error = fcntl(fd, F_SETLK, &l) == -1 ? errno : 0;
time_enable_restart();
if (!error) {
git://git.onelab.eu / sliver-openvswitch.git / blobdiff