From b38f60db0e7cdc2bfb93f0bd520ebc6cc56c0948 Mon Sep 17 00:00:00 2001 From: Sam Gross Date: Fri, 21 Mar 2025 14:22:37 -0400 Subject: [PATCH] gh-117657: Fix TSAN data race in _PyEval_SetTrace assertion (gh-131561) The `sys_tracing_threads` variable should be read inside `LOCK_SETUP()`. (cherry picked from commit 0de5e0c5442abddbe17481ef450e4abc992058f5) Co-authored-by: Sam Gross --- Python/legacy_tracing.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Python/legacy_tracing.c b/Python/legacy_tracing.c index 9cc3af1f5e162c..8a9ad3601a379e 100644 --- a/Python/legacy_tracing.c +++ b/Python/legacy_tracing.c @@ -596,10 +596,10 @@ _PyEval_SetTrace(PyThreadState *tstate, Py_tracefunc func, PyObject *arg) if (_PySys_Audit(current_tstate, "sys.settrace", NULL) < 0) { return -1; } - assert(tstate->interp->sys_tracing_threads >= 0); // needs to be decref'd outside of the lock PyObject *old_traceobj; LOCK_SETUP(); + assert(tstate->interp->sys_tracing_threads >= 0); Py_ssize_t tracing_threads = setup_tracing(tstate, func, arg, &old_traceobj); UNLOCK_SETUP(); Py_XDECREF(old_traceobj);