tests.autotest_control: Add function for running autotest in background

Add two helper functions run_autotest_background()
  & wait_autotest_background().
  Some testcases(ioquit,net_perf2,suspendresume) need run_autotest_background()
  to add workload. Both functions are wrapper of run_autotest thus place them
  in run_autotest.py. If we want to use them, we should import test.autotest
  first.
Signed-off-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NAmos Kong <akong@redhat.com>

We have update virt/tests/autotest.py to guest_autotest.py
So run_autotest() have to rename to run_guest_autotest()
Signed-off-by: NFeng Yang <fyang@redhat.com>

interface update
Signed-off-by: NFeng Yang <fyang@redhat.com>
Signed-off-by: NYiqiao Pu <ypu@redhat.com>

tests/autotest_control.py

-import os
+import os, logging, sys
+from autotest.client.shared import error
 from virttest import utils_test
 
 
@@ -6,7 +7,7 @@ def run_autotest_control(test, params, env):
     """
     Run an autotest test inside a guest.
 
-    @param test: kvm test object.
+    @param test: QEMU test object.
     @param params: Dictionary with test parameters.
     @param env: Dictionary with the test environment.
     """
@@ -23,3 +24,66 @@ def run_autotest_control(test, params, env):
 
     utils_test.run_autotest(vm, session, control_path, timeout, outputdir,
                             params)
+
+
+def run_autotest_control_background(test, params, env,
+                                    test_control_file="control"):
+    """
+    Wrapper of run_autotest_control() and make it run in the background through
+    fork() and let it run in the child process.
+    1) Flush the stdio.
+    2) Build test params which is recevied from arguments and used by
+       run_autotest_control()
+    3) Fork the process and let the run_autotest_control() run in the child
+    4) Catch the exception raise by run_autotest_control() and exit the child with
+       non-zero return code.
+    5) If no exception catched, reutrn 0
+
+    @param test: QEMU test object
+    @param params: Dictionary with the test parameters
+    @param env: Dictionary with test environment.
+    @param test_control_file: The control file of autotest running in the guest
+    """
+    def flush():
+        sys.stdout.flush()
+        sys.stderr.flush()
+
+    logging.info("Running autotest background ...")
+    flush()
+    pid = os.fork()
+    if pid:
+        # Parent process
+        return pid
+
+    flag_fname = "/tmp/autotest-flag-file-pid-" + str(os.getpid())
+    open(flag_fname, 'w').close()
+    try:
+        params['test_control_file'] = test_control_file
+        # Launch autotest
+        run_autotest_control(test, params, env)
+        os.remove(flag_fname)
+    except error.TestFail, message_fail:
+        logging.info("[Autotest Background FAIL] %s" % message_fail)
+        os.remove(flag_fname)
+        os._exit(1)
+    except error.TestError, message_error:
+        logging.info("[Autotest Background ERROR] %s" % message_error)
+        os.remove(flag_fname)
+        os._exit(2)
+    logging.info("[Auototest Background GOOD]")
+    os._exit(0)
+
+
+def wait_autotest_background(pid):
+    """
+    Wait for background autotest finish.
+
+    @param pid: Pid of the child process executing background autotest
+    """
+    logging.info("Waiting for background autotest to finish ...")
+
+    (pid, s) = os.waitpid(pid,0)
+    status = os.WEXITSTATUS(s)
+    if status != 0:
+        return False
+    return True