From: Kumar Aditya <kumaraditya@python.org>
Date: Mon, 21 Jul 2025 20:35:25 +0000 (+0530)
Subject: gh-136870: fix data race in `PyThreadState_Clear` on `sys_tracing_threads` (#136951)
X-Git-Tag: v3.15.0a1~893
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=f183996eb77fd2d5662c62667298c292c943ebf5;p=thirdparty%2FPython%2Fcpython.git

gh-136870: fix data race in `PyThreadState_Clear` on `sys_tracing_threads` (#136951)

In free-threading, multiple threads can be cleared concurrently as such the modifications on `sys_tracing_threads` should be done while holding the profile lock, otherwise it can race with other threads setting up profiling.
---

diff --git a/Python/pystate.c b/Python/pystate.c
index 0d4c26f92cec..04ca6edb4aaa 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -1682,6 +1682,10 @@ PyThreadState_Clear(PyThreadState *tstate)
           "PyThreadState_Clear: warning: thread still has a generator\n");
     }
 
+#ifdef Py_GIL_DISABLED
+    PyMutex_Lock(&_PyRuntime.ceval.sys_trace_profile_mutex);
+#endif
+
     if (tstate->c_profilefunc != NULL) {
         tstate->interp->sys_profiling_threads--;
         tstate->c_profilefunc = NULL;
@@ -1690,6 +1694,11 @@ PyThreadState_Clear(PyThreadState *tstate)
         tstate->interp->sys_tracing_threads--;
         tstate->c_tracefunc = NULL;
     }
+
+#ifdef Py_GIL_DISABLED
+    PyMutex_Unlock(&_PyRuntime.ceval.sys_trace_profile_mutex);
+#endif
+
     Py_CLEAR(tstate->c_profileobj);
     Py_CLEAR(tstate->c_traceobj);