Update process #6: make Process.on_sigchld() depend on Process.join()

Process.join() now disables Process.on_sigchld() by restablishing the
default handler SIG_DFL. Process.on_sigchld() calls Process.join() to
avoid calling os.waitpid() in two difference places because it could
interrupted and then resumed in the wrong place.

pkit/process.py

@@ -245,14 +245,7 @@ def __repr__(self):
 
     def on_sigchld(self, signum, sigframe):
         if self._child is not None and self._child.pid:
-            pid, status = os.waitpid(self._child.pid, os.WNOHANG)
-            if pid == self._child.pid:
-                self._exitcode = os.WEXITSTATUS(status)
-
-            if self._on_exit:
-                self._on_exit(self)
-
-            self.clean()
+            self.join()
 
     def create(self):
         """Method to be called when the process child is forked"""
@@ -320,6 +313,8 @@ def join(self, timeout=None):
         :param  timeout: Time to wait for the process exit
         :type   timeout: float
         """
+        signal.signal(signal.SIGCHLD, signal.SIG_DFL)
+
         if self._child is None:
             raise RuntimeError("Can only join a started process")
 
@@ -328,6 +323,11 @@ def join(self, timeout=None):
         except OSError:
             pass
 
+        if self._on_exit:
+            self._on_exit(self)
+
+        self.clean()
+
     def terminate(self, wait=False):
         """Forces the process to stop
 

tests/test_process.py

@@ -521,3 +521,19 @@ def test_restart_raises_with_invalid_policy(self):
             process.restart("that's definetly invalid")
 
         _collect_process(process)
+
+    def test_process_on_exit_is_called(self):
+        def acquire():
+            sem.acquire()
+
+        def release(process):
+            sem.release()
+
+        from multiprocessing import Semaphore
+        sem = Semaphore(1)
+
+        process = Process(target=acquire,
+                          on_exit=release)
+        process.start(wait=True)
+        process.join()
+        assert sem.get_value() == 1