Use the scoped loopback releaser which implements timeout and retries.

postinstall_runner_action_unittest.cc

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include <string>
 #include <vector>
@@ skipping 114 matching lines @@
   size_t r = fread(dev, 1, sizeof(dev), find_dev_cmd);
   ASSERT_GT(r, 0);
   ASSERT_LT(r, sizeof(dev));
   ASSERT_TRUE(feof(find_dev_cmd));
   fclose(find_dev_cmd);
 
   // strip trailing newline on dev
   if (dev[strlen(dev) - 1] == '\n')
     dev[strlen(dev) - 1] = '\0';
 
-  if (do_losetup)
+  scoped_ptr<ScopedLoopbackDeviceReleaser> loop_releaser;
+  if (do_losetup) {
     ASSERT_EQ(0, System(string("losetup ") + dev + " " + cwd + "/image.dat"));
+    loop_releaser.reset(new ScopedLoopbackDeviceReleaser(dev));
+  }
 
   ActionProcessor processor;
   ObjectFeederAction<InstallPlan> feeder_action;
   InstallPlan install_plan;
   install_plan.install_path = dev;
   feeder_action.set_obj(install_plan);
   PostinstallRunnerAction runner_action;
   BondActions(&feeder_action, &runner_action);
   ObjectCollectorAction<InstallPlan> collector_action;
   BondActions(&runner_action, &collector_action);
@@ skipping 18 matching lines @@
     EXPECT_TRUE(install_plan == collector_action.object());
   }
 
   struct stat stbuf;
   int rc = lstat((string(cwd) + "/postinst_called").c_str(), &stbuf);
   if (do_losetup && !do_err_script)
     ASSERT_EQ(0, rc);
   else
     ASSERT_LT(rc, 0);
 
-  if (do_losetup)
-    ASSERT_EQ(0, System(string("losetup -d ") + dev));
+  if (do_losetup) {
+    loop_releaser.reset(NULL);
+  }
   ASSERT_EQ(0, System(string("rm -f ") + cwd + "/postinst_called"));
   ASSERT_EQ(0, System(string("rm -f ") + cwd + "/image.dat"));
 }
 
 // Death tests don't seem to be working on Hardy
 TEST_F(PostinstallRunnerActionTest, DISABLED_RunAsRootDeathTest) {
   ASSERT_EQ(0, getuid());
   PostinstallRunnerAction runner_action;
   ASSERT_DEATH({ runner_action.TerminateProcessing(); },
                "postinstall_runner_action.h:.*] Check failed");
 }
 
 }  // namespace chromeos_update_engine