client/bin/site_utils.py

# 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.

import logging, os, platform, time
from autotest_lib.client.common_lib import error


class TimeoutError(error.TestError):
    """Error raised when we time out when waiting on a condition."""


def poll_for_condition(
    condition, exception=None, timeout=10, sleep_interval=0.1, desc=None):
    """Poll until a condition becomes true.

    condition: function taking no args and returning bool
    exception: exception to throw if condition doesn't become true
    timeout: maximum number of seconds to wait
    sleep_interval: time to sleep between polls
    desc: description of default TimeoutError used if 'exception' is None

    Raises:
        'exception' arg if supplied; site_utils.TimeoutError otherwise
    """
    start_time = time.time()
    while True:
        if condition():
            return
        if time.time() + sleep_interval - start_time > timeout:
            if exception:
                raise exception

            if desc:
                desc = 'Timed out waiting for condition: %s' % desc
            else:
                desc = 'Timed out waiting for unnamed condition'
            raise TimeoutError, desc

        time.sleep(sleep_interval)


def save_vm_state(checkpoint):
    """Saves the current state of the virtual machine.

    This function is a NOOP if the test is not running under a virtual machine
    with the USB serial port redirected.

    Arguments:
      checkpoint - Name used to identify this state

    Returns:
      None
    """
    # The QEMU monitor has been redirected to the guest serial port located at
    # /dev/ttyUSB0. To save the state of the VM, we just send the 'savevm'
    # command to the serial port.
    proc = platform.processor()
    if 'QEMU' in proc and os.path.exists('/dev/ttyUSB0'):
        logging.info('Saving VM state "%s"' % checkpoint)
        serial = open('/dev/ttyUSB0', 'w')
        serial.write("savevm %s\r\n" % checkpoint)
        logging.info('Done saving VM state "%s"' % checkpoint)