[Android] Fix a race condition in run_command.py.

third_party/android_testrunner/run_command.py

 #!/usr/bin/python2.4
 #
 #
 # Copyright 2007, The Android Open Source Project
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
@@ skipping 62 matching lines @@
     stdin_input: data to feed to stdin
   Returns:
     output of command
   Raises:
     errors.WaitForResponseTimedOutError if command did not complete within
       timeout_time seconds.
     errors.AbortError is command returned error code and SetAbortOnError is on.
   """
   start_time = time.time()
   so = []
-  pid = []
   global _abort_on_error, error_occurred
   error_occurred = False
 
+  if return_output:
+    output_dest = subprocess.PIPE
+  else:
+    # None means direct to stdout
+    output_dest = None
+  if stdin_input:
+    stdin_dest = subprocess.PIPE
+  else:
+    stdin_dest = None
+  pipe = subprocess.Popen(
+      cmd,
+      executable='/bin/bash',
+      stdin=stdin_dest,
+      stdout=output_dest,
+      stderr=subprocess.STDOUT,
+      shell=True)
+
   def Run():
     global error_occurred
-    if return_output:
-      output_dest = subprocess.PIPE
-    else:
-      # None means direct to stdout
-      output_dest = None
-    if stdin_input:
-      stdin_dest = subprocess.PIPE
-    else:
-      stdin_dest = None
-    pipe = subprocess.Popen(
-        cmd,
-        executable='/bin/bash',
-        stdin=stdin_dest,
-        stdout=output_dest,
-        stderr=subprocess.STDOUT,
-        shell=True)
-    pid.append(pipe.pid)
     try:
       output = pipe.communicate(input=stdin_input)[0]
       if output is not None and len(output) > 0:
         so.append(output)
     except OSError, e:
       logger.SilentLog("failed to retrieve stdout from: %s" % cmd)
       logger.Log(e)
       so.append("ERROR")
       error_occurred = True
     if pipe.returncode:
       logger.SilentLog("Error: %s returned %d error code" %(cmd,
           pipe.returncode))
       error_occurred = True
 
   t = threading.Thread(target=Run)
   t.start()
-
-  break_loop = False
-  while not break_loop:
-    if not t.isAlive():
-      break_loop = True
-
-    # Check the timeout
-    if (not break_loop and timeout_time is not None
-        and time.time() > start_time + timeout_time):
-      try:
-        os.kill(pid[0], signal.SIGKILL)
-      except OSError:
-        # process already dead. No action required.
-        pass
-
+  t.join(timeout_time)
+  if t.isAlive():
+    try:
+      pipe.kill()
+    except OSError:
+      # Can't kill a dead process.
+      pass
+    finally:
       logger.SilentLog("about to raise a timeout for: %s" % cmd)
       raise errors.WaitForResponseTimedOutError
-    if not break_loop:
-      time.sleep(0.1)
 
-  t.join()
   output = "".join(so)
   if _abort_on_error and error_occurred:
     raise errors.AbortError(msg=output)
 
   return "".join(so)
 
 
 def RunHostCommand(binary, valgrind=False):
   """Run a command on the host (opt using valgrind).
 
@@ skipping 34 matching lines @@
 def HasValgrind():
   """Check that /usr/bin/valgrind exists.
 
   We look for the fullpath to avoid picking up 'alternative' valgrind
   on the system.
 
   Returns:
     True if a system valgrind was found.
   """
   return os.path.exists("/usr/bin/valgrind")