Android: wait for at least one device if usb restart fails.

On some bots, the USB restart fails, but some devices come back
online shortly afterwards.
Rather than completely shortcut, wait for at least one device to be alive.

BUG=332356
TBR=navabi@chromium.org

Review URL: https://codereview.chromium.org/128083002

git-svn-id: http://src.chromium.org/svn/trunk/src/build@244145 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

android/buildbot/bb_device_status_check.py

@@ -225,7 +225,7 @@ def RestartUsb():
   if not os.path.isfile('/usr/bin/restart_usb'):
     print ('ERROR: Could not restart usb. /usr/bin/restart_usb not installed '
            'on host (see BUG=305769).')
-    return 1
+    return False
 
   lsusb_proc = bb_utils.SpawnCmd(['lsusb'], stdout=subprocess.PIPE)
   lsusb_output, _ = lsusb_proc.communicate()
@@ -236,7 +236,7 @@ def RestartUsb():
   usb_devices = [re.findall('Bus (\d\d\d) Device (\d\d\d)', lsusb_line)[0]
                  for lsusb_line in lsusb_output.strip().split('\n')]
 
-  failed_restart = False
+  all_restarted = True
   # Walk USB devices from leaves up (i.e reverse sorted) restarting the
   # connection. If a parent node (e.g. usb hub) is restarted before the
   # devices connected to it, the (bus, dev) for the hub can change, making the
@@ -247,14 +247,11 @@ def RestartUsb():
       return_code = bb_utils.RunCmd(['/usr/bin/restart_usb', bus, dev])
       if return_code:
         print 'Error restarting USB device /dev/bus/usb/%s/%s' % (bus, dev)
-        failed_restart = True
+        all_restarted = False
       else:
         print 'Restarted USB device /dev/bus/usb/%s/%s' % (bus, dev)
 
-  if failed_restart:
-    return 1
-
-  return 0
+  return all_restarted
 
 
 def KillAllAdb():
@@ -299,18 +296,24 @@ def main():
   if options.restart_usb:
     expected_devices = GetLastDevices(os.path.abspath(options.out_dir))
     devices = android_commands.GetAttachedDevices()
-    # Only restart usb if devices are missing
+    # Only restart usb if devices are missing.
     if set(expected_devices) != set(devices):
       KillAllAdb()
       retries = 5
-      if RestartUsb():
+      usb_restarted = True
+      if not RestartUsb():
+        usb_restarted = False
         bb_annotations.PrintWarning()
-        print "USB reset stage failed, continuing anyway."
-        retries = 0
+        print 'USB reset stage failed, wait for any device to come back.'
       while retries:
         time.sleep(1)
         devices = android_commands.GetAttachedDevices()
         if set(expected_devices) == set(devices):
+          # All devices are online, keep going.
+          break
+        if not usb_restarted and devices:
+          # The USB wasn't restarted, but there's at least one device online.
+          # No point in trying to wait for all devices.
           break
         retries -= 1