From b3b9ade4a3d3fe00d933bcd8fc5c5c755d1024f9 Mon Sep 17 00:00:00 2001
From: Stefan Krah <skrah@bytereef.org>
Date: Mon, 2 Mar 2020 21:22:36 +0100
Subject:  bpo-39776: Lock ++interp->tstate_next_unique_id. (GH-18746) (#18746)

  - Threads created by PyGILState_Ensure() could have a duplicate tstate->id.
---
 Python/pystate.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

(limited to 'Python')

diff --git a/Python/pystate.c b/Python/pystate.c
index ebc17ea5a7..4001c63ff2 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -606,13 +606,12 @@ new_threadstate(PyInterpreterState *interp, int init)
     tstate->context = NULL;
     tstate->context_ver = 1;
 
-    tstate->id = ++interp->tstate_next_unique_id;
-
     if (init) {
         _PyThreadState_Init(tstate);
     }
 
     HEAD_LOCK(runtime);
+    tstate->id = ++interp->tstate_next_unique_id;
     tstate->prev = NULL;
     tstate->next = interp->tstate_head;
     if (tstate->next)
-- 
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