gh-104690: thread_run() checks for tstate dangling pointer (#109056)

thread_run() of _threadmodule.c now calls
_PyThreadState_CheckConsistency() to check if tstate is a dangling
pointer when Python is built in debug mode.

Rename ceval_gil.c is_tstate_valid() to
_PyThreadState_CheckConsistency() to reuse it in _threadmodule.c.

1 files changed, 5 insertions, 2 deletions

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index 49f34fc..05bb497 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -1074,9 +1074,12 @@ static void
 thread_run(void *boot_raw)
 {
     struct bootstate *boot = (struct bootstate *) boot_raw;
-    PyThreadState *tstate;
+    PyThreadState *tstate = boot->tstate;
+
+    // gh-104690: If Python is being finalized and PyInterpreterState_Delete()
+    // was called, tstate becomes a dangling pointer.
+    assert(_PyThreadState_CheckConsistency(tstate));
 
-    tstate = boot->tstate;
     _PyThreadState_Bind(tstate);
     PyEval_AcquireThread(tstate);
     tstate->interp->threads.count++;