Merge "utils: _Popen: workaround Python 3.4.1+ subprocess locking bug"

1 files changed, 33 insertions, 4 deletions

diff --git a/rh/utils.py b/rh/utils.py
index c6c77e0..53c40b7 100644
--- a/rh/utils.py
+++ b/rh/utils.py
@@ -222,16 +222,16 @@ def _kill_child_process(proc, int_timeout, kill_timeout, cmd, original_handler,
     # where the Popen instance was created, but no process was generated.
     if proc.returncode is None and proc.pid is not None:
         try:
-            while proc.poll() is None and int_timeout >= 0:
+            while proc.poll_lock_breaker() is None and int_timeout >= 0:
                 time.sleep(0.1)
                 int_timeout -= 0.1
 
             proc.terminate()
-            while proc.poll() is None and kill_timeout >= 0:
+            while proc.poll_lock_breaker() is None and kill_timeout >= 0:
                 time.sleep(0.1)
                 kill_timeout -= 0.1
 
-            if proc.poll() is None:
+            if proc.poll_lock_breaker() is None:
                 # Still doesn't want to die.  Too bad, so sad, time to die.
                 proc.kill()
         except EnvironmentError as e:
@@ -239,7 +239,11 @@ def _kill_child_process(proc, int_timeout, kill_timeout, cmd, original_handler,
                   file=sys.stderr)
 
         # Ensure our child process has been reaped.
-        proc.wait()
+        kwargs = {}
+        if sys.version_info.major >= 3:
+            # ... but don't wait forever.
+            kwargs['timeout'] = 60
+        proc.wait_lock_breaker(**kwargs)
 
     if not rh.signals.relay_signal(original_handler, signum, frame):
         # Mock up our own, matching exit code for signaling.
@@ -296,6 +300,31 @@ class _Popen(subprocess.Popen):
             else:
                 raise
 
+    def _lock_breaker(self, func, *args, **kwargs):
+        """Helper to manage the waitpid lock.
+
+        Workaround https://bugs.python.org/issue25960.
+        """
+        # If the lock doesn't exist, or is not locked, call the func directly.
+        lock = getattr(self, '_waitpid_lock', None)
+        if lock is not None and lock.locked():
+            try:
+                lock.release()
+                return func(*args, **kwargs)
+            finally:
+                if not lock.locked():
+                    lock.acquire()
+        else:
+            return func(*args, **kwargs)
+
+    def poll_lock_breaker(self, *args, **kwargs):
+        """Wrapper around poll() to break locks if needed."""
+        return self._lock_breaker(self.poll, *args, **kwargs)
+
+    def wait_lock_breaker(self, *args, **kwargs):
+        """Wrapper around wait() to break locks if needed."""
+        return self._lock_breaker(self.wait, *args, **kwargs)
+
 
 # We use the keyword arg |input| which trips up pylint checks.
 # pylint: disable=redefined-builtin,input-builtin