static struct hmap lock_table = HMAP_INITIALIZER(&lock_table);
static void lockfile_unhash(struct lockfile *);
-static int lockfile_try_lock(const char *name, struct lockfile **lockfilep);
+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
* named 'filename_'. The caller is responsible for freeing the returned name,
* 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);
- error = lockfile_try_lock(lock_name, lockfilep);
+ 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: %s",
- lock_name, 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, 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)) {
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;