Backport of r65032 from trunk

Fixes Issue #874900: after an os.fork() call the threading module state is cleaned
up in the child process to prevent deadlock and report proper thread counts
if the new process uses the threading module.

1 files changed, 20 insertions, 0 deletions

diff --git a/Python/ceval.c b/Python/ceval.c
index 9bc147b78d..ddfe3c48ea 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -272,6 +272,9 @@ PyEval_ReleaseThread(PyThreadState *tstate)
 void
 PyEval_ReInitThreads(void)
 {
+	PyObject *threading, *result;
+	PyThreadState *tstate;
+
 	if (!interpreter_lock)
 		return;
 	/*XXX Can't use PyThread_free_lock here because it does too
@@ -281,6 +284,23 @@ PyEval_ReInitThreads(void)
 	interpreter_lock = PyThread_allocate_lock();
 	PyThread_acquire_lock(interpreter_lock, 1);
 	main_thread = PyThread_get_thread_ident();
+
+	/* Update the threading module with the new state.
+	 */
+	tstate = PyThreadState_GET();
+	threading = PyMapping_GetItemString(tstate->interp->modules,
+					    "threading");
+	if (threading == NULL) {
+		/* threading not imported */
+		PyErr_Clear();
+		return;
+	}
+	result = PyObject_CallMethod(threading, "_after_fork", NULL);
+	if (result == NULL)
+		PyErr_WriteUnraisable(threading);
+	else
+		Py_DECREF(result);
+	Py_DECREF(threading);
 }
 #endif