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gh-151364: Add critical sections to kqueue #151376

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2026-06-11-20-09-50.gh-issue-151364.NjsBYJ.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Add critical sections to :func:`select.kqueue` objects. Patch by Victor

@ZeroIntensity ZeroIntensity Jun 11, 2026

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Do users know what "critical sections" mean in this case? It's probably better to say something like "Fix thread-safety issues in select.kqueue objects," because that's what users care more about.

Stinner.
35 changes: 29 additions & 6 deletions Modules/selectmodule.c
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Expand Up @@ -1931,16 +1931,22 @@ static PyObject *
kqueue_event_repr(PyObject *op)
{
kqueue_event_Object *s = kqueue_event_Object_CAST(op);
return PyUnicode_FromFormat(
PyObject *res;
Py_BEGIN_CRITICAL_SECTION(self);
res = PyUnicode_FromFormat(
"<select.kevent ident=%zu filter=%d flags=0x%x fflags=0x%x "
"data=0x%llx udata=%p>",
(size_t)(s->e.ident), (int)s->e.filter, (unsigned int)s->e.flags,
(unsigned int)s->e.fflags, (long long)(s->e.data), (void *)s->e.udata);
Py_END_CRITICAL_SECTION();
return res;
}

static int
kqueue_event_init(PyObject *op, PyObject *args, PyObject *kwds)
kqueue_event_init_lock_held(PyObject *op, PyObject *args, PyObject *kwds)
{
_Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(op);

PyObject *pfd;
static char *kwlist[] = {"ident", "filter", "flags", "fflags",
"data", "udata", NULL};
Expand Down Expand Up @@ -1984,6 +1990,16 @@ kqueue_event_init(PyObject *op, PyObject *args, PyObject *kwds)
return 0;
}

static int
kqueue_event_init(PyObject *op, PyObject *args, PyObject *kwds)
{
int res;
Py_BEGIN_CRITICAL_SECTION(self);
res = kqueue_event_init_lock_held(op, args, kwds);
Py_END_CRITICAL_SECTION();
return res;
}
Comment on lines +1993 to +2001

@ZeroIntensity ZeroIntensity Jun 11, 2026

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We very rarely add locking to __init__ functions because there are few reasons to support concurrent reinitialization on a live object, and it slows the single-threaded case.


static PyObject *
kqueue_event_richcompare(PyObject *lhs, PyObject *rhs, int op)
{
Expand All @@ -1997,13 +2013,15 @@ kqueue_event_richcompare(PyObject *lhs, PyObject *rhs, int op)
kqueue_event_Object *o = (kqueue_event_Object *)rhs; // fast cast

#define CMP(a, b) ((a) != (b)) ? ((a) < (b) ? -1 : 1)
Py_BEGIN_CRITICAL_SECTION2(s, o);
result = CMP(s->e.ident, o->e.ident)
: CMP(s->e.filter, o->e.filter)
: CMP(s->e.flags, o->e.flags)
: CMP(s->e.fflags, o->e.fflags)
: CMP(s->e.data, o->e.data)
: CMP((intptr_t)s->e.udata, (intptr_t)o->e.udata)
: 0;
Py_END_CRITICAL_SECTION2();
#undef CMP

Py_RETURN_RICHCOMPARE(result, 0, op);
Expand Down Expand Up @@ -2159,6 +2177,8 @@ kqueue_tracking_remove(_selectstate *state, kqueue_queue_Object *self)
static int
kqueue_queue_internal_close(kqueue_queue_Object *self)
{
_Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(self);

int save_errno = 0;
if (self->kqfd >= 0) {
int kqfd = self->kqfd;
Expand Down Expand Up @@ -2246,7 +2266,9 @@ kqueue_queue_finalize(PyObject *op)
{
kqueue_queue_Object *self = kqueue_queue_Object_CAST(op);
PyObject *error = PyErr_GetRaisedException();
Py_BEGIN_CRITICAL_SECTION(self);
(void)kqueue_queue_internal_close(self);
Py_END_CRITICAL_SECTION();
PyErr_SetRaisedException(error);
}

Expand Down Expand Up @@ -2275,11 +2297,12 @@ select_kqueue_close_impl(kqueue_queue_Object *self)
static PyObject *
kqueue_queue_get_closed(PyObject *op, void *Py_UNUSED(closure))
{
int closed;
kqueue_queue_Object *self = kqueue_queue_Object_CAST(op);
if (self->kqfd < 0) {
Py_RETURN_TRUE;
}
Py_RETURN_FALSE;
Py_BEGIN_CRITICAL_SECTION(self);
closed = (self->kqfd < 0);
Py_END_CRITICAL_SECTION();
return PyBool_FromLong(closed);
}

/*[clinic input]
Expand Down
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