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,
+static int lockfile_try_lock(const char *name, pid_t *pidp,
struct lockfile **lockfilep);
/* Returns the name of the lockfile that would be created for locking a file
/* 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;
+ pid_t pid;
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 == EINTR) {
- COVERAGE_INC(lockfile_timeout);
- VLOG_WARN("%s: giving up on lock file after %lld ms",
- lock_name, elapsed);
- error = ETIMEDOUT;
- } else if (error) {
+
+ error = lockfile_try_lock(lock_name, &pid, 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));
+ 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, strerror(error));
+ }
}
free(lock_name);
}
static int
-lockfile_try_lock(const char *name, bool block, struct lockfile **lockfilep)
+lockfile_try_lock(const char *name, pid_t *pidp, struct lockfile **lockfilep)
{
struct flock l;
struct stat s;
int fd;
*lockfilep = NULL;
+ *pidp = 0;
/* Check whether we've already got a lock on that file. */
if (!stat(name, &s)) {
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) {
*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;