[3.8] gh-112275: Fix HEAD_LOCK deadlock in child process after fork (GH-112336) (GH-123688) (#123713)

miss-islington · ambv · ChuBoning · web-flow · commit e742f995efc5 · 2024-09-05T11:14:03.000+02:00
HEAD_LOCK is called from _PyEval_ReInitThreads->_PyThreadState_DeleteExcept before _PyRuntimeState_ReInitThreads reinit runtime->interpreters.mutex which might be locked before fork. (cherry picked from commit 522799a) (cherry picked from commit 0152431) Co-authored-by: Łukasz Langa <lukasz@langa.pl> Co-authored-by: ChuBoning <102216855+ChuBoning@users.noreply.github.com>
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2024-09-04-18-20-11.gh-issue-112275.W_iMiB.rst b/Misc/NEWS.d/next/Core_and_Builtins/2024-09-04-18-20-11.gh-issue-112275.W_iMiB.rst
@@ -0,0 +1,3 @@
+A deadlock involving ``pystate.c``'s ``HEAD_LOCK`` in ``posixmodule.c``
+at fork is now fixed. Patch by ChuBoning based on previous Python 3.12
+fix by Victor Stinner.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
@@ -472,10 +472,10 @@ PyOS_AfterFork_Child(void)
 {
     _PyRuntimeState *runtime = &_PyRuntime;
     _PyGILState_Reinit(runtime);
+    _PyRuntimeState_ReInitThreads(runtime);
     _PyEval_ReInitThreads(runtime);
     _PyImport_ReInitLock();
     _PySignal_AfterFork();
-    _PyRuntimeState_ReInitThreads(runtime);
     _PyInterpreterState_DeleteExceptMain(runtime);
 
     run_at_forkers(_PyInterpreterState_Get()->after_forkers_child, 0);

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	+A deadlock involving ``pystate.c``'s ``HEAD_LOCK`` in ``posixmodule.c``
	`2`	`+at fork is now fixed. Patch by ChuBoning based on previous Python 3.12`
	`3`	`+fix by Victor Stinner.`