diff --git includes/lock.inc includes/lock.inc
index 6dd4b93..4601609 100644
--- includes/lock.inc
+++ includes/lock.inc
@@ -188,7 +188,7 @@ function lock_may_be_available($name) {
  * lock. This will block further execution until the lock is available or the
  * specified delay in seconds is reached. This should not be used with locks
  * that are acquired very frequently, since the lock is likely to be acquired
- * again by a different request during the sleep().
+ * again by a different request while waiting.
  *
  * @param $name
  *   The name of the lock.
@@ -199,12 +199,32 @@ function lock_may_be_available($name) {
  *   TRUE if the lock holds, FALSE if it is available.
  */
 function lock_wait($name, $delay = 30) {
-  $delay = (int) $delay;
-  while ($delay--) {
+  // Pause the process for short periods between calling
+  // lock_may_be_available(). This prevents hitting the database with constant
+  // database queries while waiting, which could lead to performance issues.
+  // However, if the wait period is too long, there is the potential for a
+  // large number of processes to be blocked waiting for a lock, especially
+  // if the item being rebuilt is commonly requested. To address both of these
+  // concerns, begin waiting for 25ms, but double the wait period each time
+  // until it reaches 500ms. After this point polling will continue every 500ms
+  // until $delay is reached.
+
+  // $delay is passed in seconds, but we will be using usleep(), which takes
+  // microseconds as a parameter. Multiply it by 1 million so that all
+  // further numbers are equivalent.
+  $delay = (int) $delay * 1000000;
+
+  // Begin sleeping at 25ms.
+  $sleep = 25000;
+  while ($delay > 0) {
     // This function should only be called by a request that failed to get a
     // lock, so we sleep first to give the parallel request a chance to finish
     // and release the lock.
-    sleep(1);
+    usleep($sleep);
+    // After each sleep, double the value of $sleep until it reaches
+    // 500ms, to reduce the potential for a lock stampede.
+    $delay = $delay - $sleep;
+    $sleep = min(array(500000, $sleep + 25000, $delay));
     if (lock_may_be_available($name)) {
       // No longer need to wait.
       return FALSE;