Fix multiprocessing Pool throw exception in pool would hang the program. Call original signal handler and re-flush stdout.

Add py2.7 support for get_current_thread_id.

trains/task.py

@@ -55,6 +55,7 @@ from .utilities.proxy_object import ProxyDictPreWrite, ProxyDictPostWrite, flatt
     nested_from_flat_dictionary, naive_nested_from_flat_dictionary
 from .utilities.resource_monitor import ResourceMonitor
 from .utilities.seed import make_deterministic
+from .utilities.lowlevel.threads import get_current_thread_id
 # noinspection PyProtectedMember
 from .backend_interface.task.args import _Arguments
 
@@ -2307,7 +2308,7 @@ class Task(_Task):
 
     def _at_exit(self):
         # protect sub-process at_exit (should never happen)
-        if self._at_exit_called:
+        if self._at_exit_called and self._at_exit_called != get_current_thread_id():
             return
         # shutdown will clear the main, so we have to store it before.
         # is_main = self.is_main_task()
@@ -2324,14 +2325,22 @@ class Task(_Task):
         """
         # protect sub-process at_exit
         if self._at_exit_called:
+            # if we are called twice (signal in the middle of the shutdown),
+            # make sure we flush stdout, this is the best we can do.
+            if self._at_exit_called == get_current_thread_id() and self._logger and self.__is_subprocess():
+                self._logger.set_flush_period(None)
+                # noinspection PyProtectedMember
+                self._logger._close_stdout_handler(wait=True)
+                self._at_exit_called = True
             return
 
+        # from here only a single thread can re-enter
+        self._at_exit_called = get_current_thread_id()
+
         is_sub_process = self.__is_subprocess()
 
         # noinspection PyBroadException
         try:
-            # from here do not get into watch dog
-            self._at_exit_called = True
             wait_for_uploads = True
             # first thing mark task as stopped, so we will not end up with "running" on lost tasks
             # if we are running remotely, the daemon will take care of it
@@ -2464,6 +2473,9 @@ class Task(_Task):
                 pass
             self._edit_lock = None
 
+        # make sure no one will re-enter the shutdown method
+        self._at_exit_called = True
+
     @classmethod
     def __register_at_exit(cls, exit_callback, only_remove_signal_and_exception_hooks=False):
         class ExitHooks(object):
@@ -2556,8 +2568,11 @@ class Task(_Task):
                 if self._signal_recursion_protection_flag:
                     # call original
                     org_handler = self._org_handlers.get(sig)
-                    if isinstance(org_handler, Callable):
+                    if callable(org_handler):
                         org_handler = org_handler(sig, frame)
+                    else:
+                        signal.signal(sig, org_handler or signal.SIG_DFL)
+                        os.kill(os.getpid(), sig)
                     return org_handler
 
                 self._signal_recursion_protection_flag = True
@@ -2571,12 +2586,13 @@ class Task(_Task):
                         pass
                 # call original signal handler
                 org_handler = self._org_handlers.get(sig)
-                if isinstance(org_handler, Callable):
-                    # noinspection PyBroadException
-                    try:
-                        org_handler = org_handler(sig, frame)
-                    except Exception:
-                        org_handler = signal.SIG_DFL
+                self._org_handlers[sig] = None
+                if callable(org_handler):
+                    ret = org_handler(sig, frame)
+                else:
+                    signal.signal(sig, org_handler or signal.SIG_DFL)
+                    ret = 0
+
                 # remove stdout logger, just in case
                 # noinspection PyBroadException
                 try:
@@ -2584,9 +2600,14 @@ class Task(_Task):
                     Logger._remove_std_logger()
                 except Exception:
                     pass
+
+                if not callable(org_handler):
+                    os.kill(os.getpid(), sig)
+
                 self._signal_recursion_protection_flag = False
+
                 # return handler result
-                return org_handler
+                return ret
 
         # we only remove the signals since this will hang subprocesses
         if only_remove_signal_and_exception_hooks:

trains/utilities/lowlevel/threads.py

@@ -1,9 +1,14 @@
 import ctypes
 import threading
+import six
 import sys
 import time
 
 
+def get_current_thread_id():
+    return threading._get_ident() if six.PY2 else threading.get_ident()
+
+
 # Nasty hack to raise exception for other threads
 def _lowlevel_async_raise(thread_obj, exception=None):
     NULL = 0