autotest: fix race condition between cron crash_sender and test invoked

client/bin/site_crash_test.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, re
 from autotest_lib.client.bin import site_log_reader, site_utils, test
 from autotest_lib.client.common_lib import error, utils
 
 
 class CrashTest(test.test):
 
     _CONSENT_FILE = '/home/chronos/Consent To Send Stats'
     _CRASH_REPORTER_PATH = '/sbin/crash_reporter'
     _CRASH_SENDER_PATH = '/sbin/crash_sender'
     _CRASH_SENDER_RATE_DIR = '/var/lib/crash_sender'
     _CRASH_SENDER_RUN_PATH = '/var/run/crash_sender.pid'
     _MOCK_CRASH_SENDING = '/tmp/mock-crash-sending'
     _PAUSE_FILE = '/var/lib/crash_sender_paused'
     _SYSTEM_CRASH_DIR = '/var/spool/crash'
     _USER_CRASH_DIR = '/home/chronos/user/crash'
 
-    def _set_sending(self, is_enabled):
+    def _set_system_sending(self, is_enabled):
+        """Sets whether or not the system crash_sender is allowed to run.
+
+        crash_sender may still be allowed to run if _set_child_sending is
+        called with true and it is run as a child process."""
         if is_enabled:
             if os.path.exists(self._PAUSE_FILE):
                 os.remove(self._PAUSE_FILE)
         else:
             utils.system('touch ' + self._PAUSE_FILE)
 
 
+    def _set_child_sending(self, is_enabled):
+        """Overrides crash sending enabling for child processes."""
+        if is_enabled:
+            os.environ['OVERRIDE_PAUSE_SENDING'] = "1"
+        else:
+            del os.environ['OVERRIDE_PAUSE_SENDING']
+
+
     def _reset_rate_limiting(self):
         utils.system('rm -rf ' + self._CRASH_SENDER_RATE_DIR)
 
 
     def _clear_spooled_crashes(self):
         utils.system('rm -rf ' + self._SYSTEM_CRASH_DIR)
         utils.system('rm -rf ' + self._USER_CRASH_DIR)
 
 
     def _kill_running_sender(self):
@@ skipping 205 matching lines @@
     def initialize(self):
         test.test.initialize(self)
         self._log_reader = site_log_reader.LogReader()
         self._leave_crash_sending = True
         self._automatic_consent_saving = True
 
 
     def cleanup(self):
         self._reset_rate_limiting()
         self._clear_spooled_crashes()
-        self._set_sending(self._leave_crash_sending)
+        self._set_system_sending(self._leave_crash_sending)
         self._set_sending_mock(mock_enabled=False)
         if self._automatic_consent_saving:
             self._pop_consent()
         test.test.cleanup(self)
 
 
     def run_crash_tests(self,
                         test_names,
                         initialize_crash_reporter=False,
                         clear_spool_first=True,
@@ skipping 14 matching lines @@
             for attr in dir(self):
                 if attr.find('_test_') == 0:
                     test_name = attr[6:]
                     if not test_name in test_names:
                         raise error.TestError('Test %s is missing' % test_name)
 
         for test_name in test_names:
             logging.info(('=' * 20) + ('Running %s' % test_name) + ('=' * 20))
             if initialize_crash_reporter:
                 self._initialize_crash_reporter()
-            # Disable crash_sender and kill off any running ones.
-            self._set_sending(False)
+            # Disable crash_sender from running, kill off any running ones, but
+            # set environment so crash_sender may run as a child process.
+            self._set_system_sending(False)
+            self._set_child_sending(True)
             self._kill_running_sender()
             self._reset_rate_limiting()
             if clear_spool_first:
                 self._clear_spooled_crashes()
-            self._set_sending(False)
             getattr(self, '_test_' + test_name)()