--- commerce.controller.inc 2011-12-08 15:59:41.000000000 +0000
+++ commerce.controller.new.inc 2011-12-08 16:34:18.000000000 +0000
@@ -13,6 +13,12 @@
    * Stores our transaction object, necessary for pessimistic locking to work.
    */
   protected $controllerTransaction = NULL;
+
+  /**
+   * Stores ids of locked entities, necessary for knowing when to
+   * release the lock by committing the transaction.
+   */
+  protected $lockedEntities = array();

   /**
    * Override of DrupalDefaultEntityController::buildQuery().
@@ -29,6 +35,7 @@
         $this->controllerTransaction = db_transaction();
       }

+      $this->lockedEntities += array_flip($ids);
       $query->forUpdate();
     }

@@ -37,12 +44,29 @@

   public function resetCache(array $ids = NULL) {
     parent::resetCache($ids);
-    if (empty($this->entityCache) && !empty($this->controllerTransaction)) {
-      // If we don't have any entity in our local cache anymore, we commit the
-      // transaction so as to remove the locks we acquired.
-      // This will not commit the translation directly. Drupal will commit
-      // it as soon as possible given the state of the transaction stack.
-      unset($this->controllerTransaction);
+
+    // Maintain the list of locked entities, so that the releaeLock() method
+    // can know when it's time to commit the transaction.
+    if (!empty($this->lockedEntities)) {
+      foreach ($ids as $id) {
+        unset($this->lockedEntities[$id]);
+      }
+    }
+    // Try to release the lock, if possible.
+    $this->releaseLock();
+  }
+
+  /**
+   * Checks the list of tracked locked entities, and if it's empty, commits
+   * the transaction in order to remove the acquired locks.
+   * The transaction is not committed directly, Drupal commits it as soon
+   * as possible given the state of the transaction stack.
+   */
+  protected function releaseLock() {
+    if (isset($this->entityInfo['locking mode']) && $this->entityInfo['locking mode'] == 'pessimistic') {
+      if (empty($this->lockedEntities)) {
+        unset($this->controllerTransaction);
+      }
     }
   }

@@ -194,8 +218,13 @@
         ->execute();
       }

-      $this->resetCache(array($entity->{$this->idKey}));
       $this->invoke($op, $entity);
+      // Update the static cache so that the next entity_load() is going
+      // to return this newly saved entity.
+      $this->entityCache[$entity->{$this->idKey}] = $entity;
+      // Maintain the list of locked entities and release the lock if possible.
+      unset($this->lockedEntities[$entity->{$this->idKey}]);
+      $this->releaseLock();

       // Ignore slave server temporarily.
       db_ignore_slave();