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[3.13] gh-117657: Fix race involving immortalizing objects (GH-119927) (#120005)

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The free-threaded build currently immortalizes objects that use deferred
reference counting (see gh-117783). This typically happens once the
first non-main thread is created, but the behavior can be suppressed for
tests, in subinterpreters, or during a compile() call.

This fixes a race condition involving the tracking of whether the
behavior is suppressed.

(cherry picked from commit 47fb4327b5)
This commit is contained in:
Sam Gross 2024-06-03 18:21:32 -04:00 • committed by GitHub
parent ca37034baa
commit ae705319fc
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GPG key ID: B5690EEEBB952194
9 changed files with 30 additions and 44 deletions
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6
Python/bltinmodule.c
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@ -870,15 +870,15 @@ builtin_compile_impl(PyObject *module, PyObject *source, PyObject *filename,
// gh-118527: Disable immortalization of code constants for explicit
// compile() calls to get consistent frozen outputs between the default
// and free-threaded builds.
// Subtract two to suppress immortalization (so that 1 -> -1)
PyInterpreterState *interp = _PyInterpreterState_GET();
int old_value = interp->gc.immortalize.enable_on_thread_created;
interp->gc.immortalize.enable_on_thread_created = 0;
_Py_atomic_add_int(&interp->gc.immortalize, -2);
#endif
result = Py_CompileStringObject(str, filename, start[compile_mode], &cf, optimize);
#ifdef Py_GIL_DISABLED
interp->gc.immortalize.enable_on_thread_created = old_value;
_Py_atomic_add_int(&interp->gc.immortalize, 2);
#endif
Py_XDECREF(source_copy);

14
Python/gc_free_threading.c
View file

@ -703,11 +703,9 @@ _PyGC_Init(PyInterpreterState *interp)
{
GCState *gcstate = &interp->gc;
if (_Py_IsMainInterpreter(interp)) {
// gh-117783: immortalize objects that would use deferred refcounting
// once the first non-main thread is created.
gcstate->immortalize.enable_on_thread_created = 1;
}
// gh-117783: immortalize objects that would use deferred refcounting
// once the first non-main thread is created (but not in subinterpreters).
gcstate->immortalize = _Py_IsMainInterpreter(interp) ? 0 : -1;
gcstate->garbage = PyList_New(0);
if (gcstate->garbage == NULL) {
@ -1808,8 +1806,10 @@ _PyGC_ImmortalizeDeferredObjects(PyInterpreterState *interp)
{
struct visitor_args args;
_PyEval_StopTheWorld(interp);
gc_visit_heaps(interp, &immortalize_visitor, &args);
interp->gc.immortalize.enabled = 1;
if (interp->gc.immortalize == 0) {
gc_visit_heaps(interp, &immortalize_visitor, &args);
interp->gc.immortalize = 1;
}
_PyEval_StartTheWorld(interp);
}

4
Python/pystate.c
View file

@ -1583,9 +1583,7 @@ new_threadstate(PyInterpreterState *interp, int whence)
}
else {
#ifdef Py_GIL_DISABLED
if (interp->gc.immortalize.enable_on_thread_created &&
!interp->gc.immortalize.enabled)
{
if (_Py_atomic_load_int(&interp->gc.immortalize) == 0) {
// Immortalize objects marked as using deferred reference counting
// the first time a non-main thread is created.
_PyGC_ImmortalizeDeferredObjects(interp);