1 files changed, 58 insertions, 0 deletions
diff --git a/test/integration/targets/fork_safe_stdio/callback_plugins/spewstdio.py b/test/integration/targets/fork_safe_stdio/callback_plugins/spewstdio.py
new file mode 100644
index 0000000..6ed6ef3
--- /dev/null
+++ b/test/integration/targets/fork_safe_stdio/callback_plugins/spewstdio.py
@@ -0,0 +1,58 @@
+import atexit
+import os
+import sys
+
+from ansible.plugins.callback import CallbackBase
+from ansible.utils.display import Display
+from threading import Thread
+
+# This callback plugin reliably triggers the deadlock from https://github.com/ansible/ansible-runner/issues/1164 when
+# run on a TTY/PTY. It starts a thread in the controller that spews unprintable characters to stdout as fast as
+# possible, while causing forked children to write directly to the inherited stdout immediately post-fork. If a fork
+# occurs while the spew thread holds stdout's internal BufferedIOWriter lock, the lock will be orphaned in the child,
+# and attempts to write to stdout there will hang forever.
+
+# Any mechanism that ensures non-main threads do not hold locks before forking should allow this test to pass.
+
+# ref: https://docs.python.org/3/library/io.html#multi-threading
+# ref: https://github.com/python/cpython/blob/0547a981ae413248b21a6bb0cb62dda7d236fe45/Modules/_io/bufferedio.c#L268
+
+
+class CallbackModule(CallbackBase):
+    CALLBACK_VERSION = 2.0
+    CALLBACK_NAME = 'spewstdio'
+
+    def __init__(self):
+        super().__init__()
+        self.display = Display()
+
+        if os.environ.get('SPEWSTDIO_ENABLED', '0') != '1':
+            self.display.warning('spewstdio test plugin loaded but disabled; set SPEWSTDIO_ENABLED=1 to enable')
+            return
+
+        self.display = Display()
+        self._keep_spewing = True
+
+        # cause the child to write directly to stdout immediately post-fork
+        os.register_at_fork(after_in_child=lambda: print(f"hi from forked child pid {os.getpid()}"))
+
+        # in passing cases, stop spewing when the controller is exiting to prevent fatal errors on final flush
+        atexit.register(self.stop_spew)
+
+        self._spew_thread = Thread(target=self.spew, daemon=True)
+        self._spew_thread.start()
+
+    def stop_spew(self):
+        self._keep_spewing = False
+
+    def spew(self):
+        # dump a message so we know the callback thread has started
+        self.display.warning("spewstdio STARTING NONPRINTING SPEW ON BACKGROUND THREAD")
+
+        while self._keep_spewing:
+            # dump a non-printing control character directly to stdout to avoid junking up the screen while still
+            # doing lots of writes and flushes.
+            sys.stdout.write('\x1b[K')
+            sys.stdout.flush()
+
+        self.display.warning("spewstdio STOPPING SPEW")