function lock_may_be_available

Same name and namespace in other branches

1. 6.x drupal-6.x/includes/lock-install.inc \lock_may_be_available()
2. 6.x drupal-6.x/includes/lock.inc \lock_may_be_available()

Check if lock acquired by a different process may be available.

If an existing lock has expired, it is removed.

Parameters

$name: The name of the lock.

Return value

TRUE if there is no lock or it was removed, FALSE otherwise.

Related topics

2 calls to lock_may_be_available()

lock_acquire in drupal-7.x/includes/lock.inc

Acquire (or renew) a lock, but do not block if it fails.

lock_wait in drupal-7.x/includes/lock.inc

Wait for a lock to be available.

Archivo

drupal-7.x/includes/lock.inc, line 166

A database-mediated implementation of a locking mechanism.

Código

function lock_may_be_available($name) {
  $lock = db_query('SELECT expire, value FROM {semaphore} WHERE name = :name', array(':name' => $name))->fetchAssoc();
  if (!$lock) {
    return TRUE;
  }
  $expire = (float) $lock['expire'];
  $now = microtime(TRUE);
  if ($now > $expire) {
    // We check two conditions to prevent a race condition where another
    // request acquired the lock and set a new expire time. We add a small
    // number to $expire to avoid errors with float to string conversion.
    return (bool) db_delete('semaphore')->condition('name', $name)->condition('value', $lock['value'])->condition('expire', 0.0001 + $expire, '<=')->execute();
  }
  return FALSE;
}