[testrunner] Prevent erroneous overriding of signal handlers

When an overall timeout is reached, swarming sends a SIGTERM to
terminate the test runner. The test runner has a signal handler on the
main process to terminate all workers gracefully.

Additionally, every worker process installs a signal handler for
terminating ongoing tests wrapped by command.Command.

Also, command.Command is used on the main process to list tests for
cctest and gtest executables, which led to overriding the test runner's
main signal handler.

This CL disables using signal handlers in commands by default and only
explicitly enables it in safe source locations.

Bug: v8:8292
Change-Id: Ifceadaff75bdd2b77e761498bccbe00b6a3e265c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2002528
Reviewed-by: Tamer Tas <tmrts@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65815}

tools/predictable_wrapper.py

@@ -37,7 +37,8 @@ def main(args):
         return line
     return None
 
-  cmd = command.Command(args[0], args[1:], timeout=TIMEOUT)
+  cmd = command.Command(
+      args[0], args[1:], timeout=TIMEOUT, handle_sigterm=True)
 
   previous_allocations = None
   for run in range(1, MAX_TRIES + 1):

tools/run_perf.py

@@ -479,7 +479,8 @@ class RunnableConfig(GraphConfig):
         cmd_prefix=cmd_prefix,
         shell=os.path.join(shell_dir, self.binary),
         args=self.GetCommandFlags(extra_flags=extra_flags),
-        timeout=self.timeout or 60)
+        timeout=self.timeout or 60,
+        handle_sigterm=True)
 
   def ProcessOutput(self, output, result_tracker, count):
     """Processes test run output and updates result tracker.

tools/testrunner/local/command.py

@@ -41,7 +41,7 @@ class AbortException(Exception):
 
 class BaseCommand(object):
   def __init__(self, shell, args=None, cmd_prefix=None, timeout=60, env=None,
-               verbose=False, resources_func=None):
+               verbose=False, resources_func=None, handle_sigterm=False):
     """Initialize the command.
 
     Args:
@@ -52,6 +52,9 @@ class BaseCommand(object):
       env: Environment dict for execution.
       verbose: Print additional output.
       resources_func: Callable, returning all test files needed by this command.
+      handle_sigterm: Flag indicating if SIGTERM will be used to terminate the
+          underlying process. Should not be used from the main thread, e.g. when
+          using a command to list tests.
     """
     assert(timeout > 0)
 
@@ -61,6 +64,7 @@ class BaseCommand(object):
     self.timeout = timeout
     self.env = env or {}
     self.verbose = verbose
+    self.handle_sigterm = handle_sigterm
 
   def execute(self):
     if self.verbose:
@@ -72,7 +76,9 @@ class BaseCommand(object):
     abort_occured = [False]
     def handler(signum, frame):
       self._abort(process, abort_occured)
-    signal.signal(signal.SIGTERM, handler)
+
+    if self.handle_sigterm:
+      signal.signal(signal.SIGTERM, handler)
 
     # Variable to communicate with the timer.
     timeout_occured = [False]

tools/testrunner/objects/testcase.py

@@ -271,6 +271,7 @@ class TestCase(object):
       timeout=timeout,
       verbose=self._test_config.verbose,
       resources_func=self._get_resources,
+      handle_sigterm=True,
     )
 
   def _parse_source_flags(self, source=None):

tools/unittests/run_perf_test.py

@@ -191,7 +191,8 @@ class PerfTest(unittest.TestCase):
         cmd_prefix=[],
         shell=shell,
         args=list(args),
-        timeout=kwargs.get('timeout', 60))
+        timeout=kwargs.get('timeout', 60),
+        handle_sigterm=True)
 
   def _VerifyMockMultiple(self, *args, **kwargs):
     self.assertEqual(len(args), len(command.Command.call_args_list))
@@ -200,7 +201,8 @@ class PerfTest(unittest.TestCase):
         'cmd_prefix': [],
         'shell': os.path.join(os.path.dirname(BASE_DIR), arg[0]),
         'args': list(arg[1:]),
-        'timeout': kwargs.get('timeout', 60)
+        'timeout': kwargs.get('timeout', 60),
+        'handle_sigterm': True,
       }
       self.assertTupleEqual((expected, ), actual)