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gh-116738: make entering of contextvars.Context thread safe (#143074)

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Kumar Aditya 2026-01-06 12:24:02 +05:30 committed by GitHub
parent 12d363bb66
commit d6f77e6a3f
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2 changed files with 11 additions and 5 deletions
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1
Misc/NEWS.d/next/Core_and_Builtins/2025-12-22-16-22-02.gh-issue-116738.caQuq_.rst Normal file
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@ -0,0 +1 @@
Fix thread safety of :func:`contextvars.Context.run`.

15
Python/context.c
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@ -195,16 +195,20 @@ _PyContext_Enter(PyThreadState *ts, PyObject *octx)
{
ENSURE_Context(octx, -1)
PyContext *ctx = (PyContext *)octx;
#ifdef Py_GIL_DISABLED
int already_entered = _Py_atomic_exchange_int(&ctx->ctx_entered, 1);
#else
int already_entered = ctx->ctx_entered;
ctx->ctx_entered = 1;
#endif
if (ctx->ctx_entered) {
if (already_entered) {
_PyErr_Format(ts, PyExc_RuntimeError,
"cannot enter context: %R is already entered", ctx);
return -1;
}
ctx->ctx_prev = (PyContext *)ts->context; /* borrow */
ctx->ctx_entered = 1;
ts->context = Py_NewRef(ctx);
context_switched(ts);
return 0;
@ -225,8 +229,9 @@ _PyContext_Exit(PyThreadState *ts, PyObject *octx)
{
ENSURE_Context(octx, -1)
PyContext *ctx = (PyContext *)octx;
int already_entered = FT_ATOMIC_LOAD_INT_RELAXED(ctx->ctx_entered);
if (!ctx->ctx_entered) {
if (!already_entered) {
PyErr_Format(PyExc_RuntimeError,
"cannot exit context: %R has not been entered", ctx);
return -1;
@ -243,7 +248,7 @@ _PyContext_Exit(PyThreadState *ts, PyObject *octx)
Py_SETREF(ts->context, (PyObject *)ctx->ctx_prev);
ctx->ctx_prev = NULL;
ctx->ctx_entered = 0;
FT_ATOMIC_STORE_INT(ctx->ctx_entered, 0);
context_switched(ts);
return 0;
}