static void create_lockfile(void)
{
char pid_str[sizeof(long)*3 + 4];
sprintf(pid_str, "%lu", (long)getpid());
char *lock_filename = concat_path_file(g_settings_dump_location, "post-create.lock");
/* Someone else's post-create may take a long-ish time to finish.
* For example, I had a failing email sending there, it took
* a minute to time out.
* That's why timeout is large (100 seconds):
*/
int count = 100;
while (1)
{
/* Return values:
* -1: error (in this case, errno is 0 if error message is already logged)
* 0: failed to lock (someone else has it locked)
* 1: success
*/
int r = create_symlink_lockfile(lock_filename, pid_str);
if (r > 0)
break;
if (r < 0)
error_msg_and_die("Can't create '%s'", lock_filename);
if (--count == 0)
{
/* Someone else's post-create process is alive but stuck.
* Don't wait forever.
*/
error_msg("Stale lock '%s', removing it", lock_filename);
xunlink(lock_filename);
break;
}
sleep(1);
}
free(lock_filename);
}
static int dd_lock(struct dump_dir *dd, unsigned sleep_usec, int flags)
{
if (dd->locked)
error_msg_and_die("Locking bug on '%s'", dd->dd_dirname);
char pid_buf[sizeof(long)*3 + 2];
snprintf(pid_buf, sizeof(pid_buf), "%lu", (long)getpid());
unsigned dirname_len = strlen(dd->dd_dirname);
char lock_buf[dirname_len + sizeof("/.lock")];
strcpy(lock_buf, dd->dd_dirname);
strcpy(lock_buf + dirname_len, "/.lock");
unsigned count = NO_TIME_FILE_COUNT;
retry:
while (1)
{
int r = create_symlink_lockfile(lock_buf, pid_buf);
if (r < 0)
return r; /* error */
if (r > 0 || errno == EALREADY)
break; /* locked successfully */
/* Other process has the lock, wait for it to go away */
usleep(sleep_usec);
}
/* Reset errno to 0 only if errno is EALREADY (used by
* create_symlink_lockfile() to signal that the dump directory is already
* locked by us) */
if (!(dd->owns_lock = (errno != EALREADY)))
errno = 0;
/* Are we called by dd_opendir (as opposed to dd_create)? */
if (sleep_usec == WAIT_FOR_OTHER_PROCESS_USLEEP) /* yes */
{
const char *missing_file = dd_check(dd);
/* some of the required files don't exist. We managed to lock the directory
* which was just created by somebody else, or is almost deleted
* by delete_file_dir.
* Unlock and back off.
*/
if (missing_file)
{
if (dd->owns_lock)
xunlink(lock_buf);
log_warning("Unlocked '%s' (no or corrupted '%s' file)", lock_buf, missing_file);
if (--count == 0 || flags & DD_DONT_WAIT_FOR_LOCK)
{
errno = EISDIR; /* "this is an ordinary dir, not dump dir" */
return -1;
}
usleep(NO_TIME_FILE_USLEEP);
goto retry;
}
}
dd->locked = true;
return 0;
}
