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gh-84579: Fixed a deadlock issue in the bufferedIO module when using fork in Py… #128591

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gh-84579: Fixed a deadlock issue in the bufferedIO module when using fork in Py… #128591

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66 changes: 66 additions & 0 deletions Modules/_io/bufferedio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -737,6 +737,8 @@ static PyObject *
_bufferedreader_read_generic(buffered *self, Py_ssize_t);
static Py_ssize_t
_bufferedreader_raw_read(buffered *self, char *start, Py_ssize_t len);
static int
_buffered_init(buffered *self);

/*
* Helpers
Expand Down Expand Up @@ -825,6 +827,60 @@ _buffered_raw_seek(buffered *self, Py_off_t target, int whence)
return n;
}

#ifdef HAVE_FORK

static PyObject*
buffered_after_fork_child_impl(PyObject *self, PyObject *Py_UNUSED(ignored))
{
buffered *buf = (buffered *)self;
if (_buffered_init(buf) < 0) {
PyErr_SetString(PyExc_RuntimeError, "Failed to initialize buffer after fork");
return NULL;
}
_bufferedreader_reset_buf(buf);
Py_RETURN_NONE;
}

static PyMethodDef buffered_fork_methods[] = {
{"_after_fork_child", buffered_after_fork_child_impl, METH_NOARGS, NULL},
{NULL, NULL}
};

static int
buffered_register_at_fork(buffered *self)
{
PyInterpreterState *interp = PyThreadState_Get()->interp;
if (!interp) {
PyErr_SetString(PyExc_RuntimeError, "Failed to get interpreter state");
return -1;
}

// Only register the fork handlers once
if (!interp->after_forkers_child) {
interp->after_forkers_child = PyList_New(0);
if (!interp->after_forkers_child) {
return -1;
}
}

/* Create method objects */
PyObject *after_child = PyCFunction_New(&buffered_fork_methods[0], (PyObject *)self);
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For me, this is not true here.

If you try to register a callback for every buffer object. I think there would be memory leak here.

if (!after_child) {
return -1;
}

/* Append callbacks to the lists */
int status = 0;
if (PyList_Append(interp->after_forkers_child, after_child) < 0) {
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If I'm correct, I think the length of after_forkers_child will raising unlimited？

status = -1;
}

Py_DECREF(after_child);
return status;
}

#endif /* HAVE_FORK */

static int
_buffered_init(buffered *self)
{
Expand Down Expand Up @@ -859,6 +915,16 @@ _buffered_init(buffered *self)
self->buffer_mask = 0;
if (_buffered_raw_tell(self) == -1)
PyErr_Clear();

#ifdef HAVE_FORK
/* Register fork handlers */
if (buffered_register_at_fork(self) < 0) {
PyThread_free_lock(self->lock);
self->lock = NULL;
return -1;
}
#endif /* HAVE_FORK */

return 0;
}

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