[3.11] pythongh-106883 Fix deadlock in threaded application

diegorusso · diegorusso · commit 9937d7e4911a · 2024-03-28T17:35:12.000Z
When using threaded applications, there is a high risk of a deadlock in
the intepreter.
It's a lock ordering deadlock with HEAD_LOCK(&amp;_PyRuntime); and the GIL.

It has been suggested to disable GC during the
_PyThread_CurrentFrames() and _PyThread_CurrentExceptions() calls.

Jira: ENTLLT-7285

Change-Id: I2548d07803fc98db8717057ae3006e6af68b2f86
diff --git a/Python/pystate.c b/Python/pystate.c
@@ -2,6 +2,7 @@
 /* Thread and interpreter state structures and their interfaces */
 
 #include "Python.h"
+#include "objimpl.h"
 #include "pycore_ceval.h"
 #include "pycore_code.h"           // stats
 #include "pycore_frame.h"
@@ -1388,6 +1389,10 @@ PyThreadState_Next(PyThreadState *tstate) {
 PyObject *
 _PyThread_CurrentFrames(void)
 {
+    // Disable the GC as this can cause a deadlock the interpreter.
+    // See issues 116969 and 106883.
+    PyGC_Disable();
+
     PyThreadState *tstate = _PyThreadState_GET();
     if (_PySys_Audit(tstate, "sys._current_frames", NULL) < 0) {
         return NULL;
@@ -1440,12 +1445,20 @@ _PyThread_CurrentFrames(void)
 
 done:
     HEAD_UNLOCK(runtime);
+
+    // Once we release the runtime, the GC can be reenabled.
+    PyGC_Enable();
+
     return result;
 }
 
 PyObject *
 _PyThread_CurrentExceptions(void)
 {
+    // Disable the GC as this can cause a deadlock the interpreter.
+    // See issues 116969 and 106883.
+    PyGC_Disable();
+
     PyThreadState *tstate = _PyThreadState_GET();
 
     _Py_EnsureTstateNotNULL(tstate);
@@ -1499,6 +1512,10 @@ _PyThread_CurrentExceptions(void)
 
 done:
     HEAD_UNLOCK(runtime);
+
+    // Once we release the runtime, the GC can be reenabled.
+    PyGC_Enable();
+
     return result;
 }
 
