emulator: Add option "--debug-tags" for avd start

Also enable snapshot debugging when "snapshot" option is set for avd create.
Plus some minor fixes for root_ini and logging for emulator start

Bug: 922145
Change-Id: I6aaebc099ce25e9180efb6a66c097f885b804db2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2145957Reviewed-by: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Auto-Submit: Haiyang Pan <hypan@google.com>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758862}

build/android/pylib/local/emulator/avd.py

@@ -236,8 +236,9 @@ class AvdConfig(object):
       avd_dir = os.path.join(android_avd_home, '%s.avd' % self._config.avd_name)
       config_ini = os.path.join(avd_dir, 'config.ini')
 
-      with open(root_ini, 'a') as root_ini_file:
-        root_ini_file.write('path.rel=avd/%s.avd\n' % self._config.avd_name)
+      if os.path.exists(root_ini):
+        with open(root_ini, 'a') as root_ini_file:
+          root_ini_file.write('path.rel=avd/%s.avd\n' % self._config.avd_name)
 
       if os.path.exists(config_ini):
         with open(config_ini) as config_ini_file:
@@ -263,7 +264,10 @@ class AvdConfig(object):
       self._Initialize()
       instance = _AvdInstance(self._emulator_path, self._emulator_home,
                               self._config)
-      instance.Start(read_only=False, snapshot_save=snapshot)
+      # Enable debug for snapshot when it is set to True
+      debug_tags = 'snapshot' if snapshot else None
+      instance.Start(
+          read_only=False, snapshot_save=snapshot, debug_tags=debug_tags)
       device_utils.DeviceUtils(instance.serial).WaitUntilFullyBooted(
           timeout=180, retries=0)
       instance.Stop()
@@ -496,7 +500,8 @@ class _AvdInstance(object):
             read_only=True,
             snapshot_save=False,
             window=False,
-            writable_system=False):
+            writable_system=False,
+            debug_tags=None):
     """Starts the emulator running an instance of the given AVD."""
 
     with tempfile_ext.TemporaryFileName() as socket_path, (contextlib.closing(
@@ -517,6 +522,8 @@ class _AvdInstance(object):
         emulator_cmd.append('-no-snapshot-save')
       if writable_system:
         emulator_cmd.append('-writable-system')
+      if debug_tags:
+        emulator_cmd.extend(['-debug', debug_tags])
 
       emulator_env = {}
       if self._emulator_home:
@@ -531,11 +538,14 @@ class _AvdInstance(object):
 
       sock.listen(1)
 
-      logging.info('Starting emulator.')
+      logging.info('Starting emulator with commands: %s',
+                   ' '.join(emulator_cmd))
 
       # TODO(jbudorick): Add support for logging emulator stdout & stderr at
       # higher logging levels.
-      self._sink = open('/dev/null', 'w')
+      # Enable the emulator log when debug_tags is set.
+      if not debug_tags:
+        self._sink = open('/dev/null', 'w')
       self._emulator_proc = cmd_helper.Popen(
           emulator_cmd, stdout=self._sink, stderr=self._sink, env=emulator_env)
 

tools/android/avd/avd.py

@@ -99,6 +99,12 @@ def main(raw_args):
       action='store_true',
       default=False,
       help='Enable graphical window display on the emulator.')
+  start_parser.add_argument(
+      '--debug-tags',
+      help='Comma-separated list of debug tags. This can be used to enable or '
+      'disable debug messages from specific parts of the emulator, e.g. '
+      'init, snapshot. See "emulator -help-debug-tags" '
+      'for a full list of tags.')
   add_common_arguments(start_parser)
 
   def start_cmd(args):
@@ -106,7 +112,8 @@ def main(raw_args):
     inst.Start(
         read_only=args.read_only,
         snapshot_save=not args.read_only,
-        window=args.emulator_window)
+        window=args.emulator_window,
+        debug_tags=args.debug_tags)
     print('%s started (pid: %d)' % (str(inst), inst._emulator_proc.pid))
     return 0