Merge _sig_chld() fix into asyncio branch.

2 files changed, 23 insertions, 20 deletions

diff --git a/asyncio/unix_events.py b/asyncio/unix_events.py
index 49761b9..b4bd15d 100644
--- a/asyncio/unix_events.py
+++ b/asyncio/unix_events.py
@@ -163,26 +163,23 @@ class SelectorEventLoop(selector_events.BaseSelectorEventLoop):
 
     def _sig_chld(self):
         try:
-            while True:
-                try:
-                    pid, status = os.waitpid(0, os.WNOHANG)
-                except ChildProcessError:
-                    break
-                if pid == 0:
-                    continue
-                elif os.WIFSIGNALED(status):
-                    returncode = -os.WTERMSIG(status)
-                elif os.WIFEXITED(status):
-                    returncode = os.WEXITSTATUS(status)
-                else:
-                    # covered by
-                    # SelectorEventLoopTests.test__sig_chld_unknown_status
-                    # from tests/unix_events_test.py
-                    # bug in coverage.py version 3.6 ???
-                    continue  # pragma: no cover
-                transp = self._subprocesses.get(pid)
-                if transp is not None:
-                    transp._process_exited(returncode)
+            try:
+                pid, status = os.waitpid(0, os.WNOHANG)
+            except ChildProcessError:
+                return
+            if pid == 0:
+                self.call_soon(self._sig_chld)
+                return
+            elif os.WIFSIGNALED(status):
+                returncode = -os.WTERMSIG(status)
+            elif os.WIFEXITED(status):
+                returncode = os.WEXITSTATUS(status)
+            else:
+                self.call_soon(self._sig_chld)
+                return
+            transp = self._subprocesses.get(pid)
+            if transp is not None:
+                transp._process_exited(returncode)
         except Exception:
             asyncio_log.exception('Unknown exception in SIGCHLD handler')
 
diff --git a/tests/test_unix_events.py b/tests/test_unix_events.py
index 42dd919..e8a9ec3 100644
--- a/tests/test_unix_events.py
+++ b/tests/test_unix_events.py
@@ -290,6 +290,12 @@ class SelectorEventLoopTests(unittest.TestCase):
         m_log.exception.assert_called_with(
             'Unknown exception in SIGCHLD handler')
 
+    @unittest.mock.patch('os.waitpid')
+    def test__sig_chld_process_error(self, m_waitpid):
+        m_waitpid.side_effect = ChildProcessError
+        self.loop._sig_chld()
+        self.assertTrue(m_waitpid.called)
+
 
 class UnixReadPipeTransportTests(unittest.TestCase):