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gh-114271: Make thread._rlock thread-safe in free-threaded builds #115102

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Merged
merged 1 commit into from
Feb 16, 2024
Merged

gh-114271: Make thread._rlock thread-safe in free-threaded builds #115102

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6 changes: 6 additions & 0 deletions Include/cpython/pyatomic.h
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Original file line number Diff line number Diff line change
Expand Up @@ -360,6 +360,8 @@ _Py_atomic_load_ssize_relaxed(const Py_ssize_t *obj);
static inline void *
_Py_atomic_load_ptr_relaxed(const void *obj);

static inline unsigned long long
_Py_atomic_load_ullong_relaxed(const unsigned long long *obj);

// --- _Py_atomic_store ------------------------------------------------------
// Atomically performs `*obj = value` (sequential consistency)
Expand Down Expand Up @@ -452,6 +454,10 @@ _Py_atomic_store_ptr_relaxed(void *obj, void *value);
static inline void
_Py_atomic_store_ssize_relaxed(Py_ssize_t *obj, Py_ssize_t value);

static inline void
_Py_atomic_store_ullong_relaxed(unsigned long long *obj,
unsigned long long value);


// --- _Py_atomic_load_ptr_acquire / _Py_atomic_store_ptr_release ------------

Expand Down
9 changes: 9 additions & 0 deletions Include/cpython/pyatomic_gcc.h
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Expand Up @@ -358,6 +358,10 @@ static inline void *
_Py_atomic_load_ptr_relaxed(const void *obj)
{ return (void *)__atomic_load_n((const void **)obj, __ATOMIC_RELAXED); }

static inline unsigned long long
_Py_atomic_load_ullong_relaxed(const unsigned long long *obj)
{ return __atomic_load_n(obj, __ATOMIC_RELAXED); }


// --- _Py_atomic_store ------------------------------------------------------

Expand Down Expand Up @@ -476,6 +480,11 @@ static inline void
_Py_atomic_store_ssize_relaxed(Py_ssize_t *obj, Py_ssize_t value)
{ __atomic_store_n(obj, value, __ATOMIC_RELAXED); }

static inline void
_Py_atomic_store_ullong_relaxed(unsigned long long *obj,
unsigned long long value)
{ __atomic_store_n(obj, value, __ATOMIC_RELAXED); }


// --- _Py_atomic_load_ptr_acquire / _Py_atomic_store_ptr_release ------------

Expand Down
14 changes: 14 additions & 0 deletions Include/cpython/pyatomic_msc.h
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Expand Up @@ -712,6 +712,12 @@ _Py_atomic_load_ptr_relaxed(const void *obj)
return *(void * volatile *)obj;
}

static inline unsigned long long
_Py_atomic_load_ullong_relaxed(const unsigned long long *obj)
{
return *(volatile unsigned long long *)obj;
}


// --- _Py_atomic_store ------------------------------------------------------

Expand Down Expand Up @@ -886,6 +892,14 @@ _Py_atomic_store_ssize_relaxed(Py_ssize_t *obj, Py_ssize_t value)
*(volatile Py_ssize_t *)obj = value;
}

static inline void
_Py_atomic_store_ullong_relaxed(unsigned long long *obj,
unsigned long long value)
{
*(volatile unsigned long long *)obj = value;
}


// --- _Py_atomic_load_ptr_acquire / _Py_atomic_store_ptr_release ------------

static inline void *
Expand Down
17 changes: 17 additions & 0 deletions Include/cpython/pyatomic_std.h
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Expand Up @@ -619,6 +619,14 @@ _Py_atomic_load_ptr_relaxed(const void *obj)
memory_order_relaxed);
}

static inline unsigned long long
_Py_atomic_load_ullong_relaxed(const unsigned long long *obj)
{
_Py_USING_STD;
return atomic_load_explicit((const _Atomic(unsigned long long)*)obj,
memory_order_relaxed);
}


// --- _Py_atomic_store ------------------------------------------------------

Expand Down Expand Up @@ -835,6 +843,15 @@ _Py_atomic_store_ssize_relaxed(Py_ssize_t *obj, Py_ssize_t value)
memory_order_relaxed);
}

static inline void
_Py_atomic_store_ullong_relaxed(unsigned long long *obj,
unsigned long long value)
{
_Py_USING_STD;
atomic_store_explicit((_Atomic(unsigned long long)*)obj, value,
memory_order_relaxed);
}


// --- _Py_atomic_load_ptr_acquire / _Py_atomic_store_ptr_release ------------

Expand Down
32 changes: 22 additions & 10 deletions Modules/_threadmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@
#include "pycore_sysmodule.h" // _PySys_GetAttr()
#include "pycore_weakref.h" // _PyWeakref_GET_REF()

#include <stdbool.h>
#include <stddef.h> // offsetof()
#ifdef HAVE_SIGNAL_H
# include <signal.h> // SIGINT
Expand Down Expand Up @@ -470,6 +471,14 @@ rlock_dealloc(rlockobject *self)
Py_DECREF(tp);
}

static bool
rlock_is_owned_by(rlockobject *self, PyThread_ident_t tid)
{
PyThread_ident_t owner_tid =
_Py_atomic_load_ullong_relaxed(&self->rlock_owner);
return owner_tid == tid && self->rlock_count > 0;
}

static PyObject *
rlock_acquire(rlockobject *self, PyObject *args, PyObject *kwds)
{
Expand All @@ -481,7 +490,7 @@ rlock_acquire(rlockobject *self, PyObject *args, PyObject *kwds)
return NULL;

tid = PyThread_get_thread_ident_ex();
if (self->rlock_count > 0 && tid == self->rlock_owner) {
if (rlock_is_owned_by(self, tid)) {
unsigned long count = self->rlock_count + 1;
if (count <= self->rlock_count) {
PyErr_SetString(PyExc_OverflowError,
Expand All @@ -494,7 +503,7 @@ rlock_acquire(rlockobject *self, PyObject *args, PyObject *kwds)
r = acquire_timed(self->rlock_lock, timeout);
if (r == PY_LOCK_ACQUIRED) {
assert(self->rlock_count == 0);
self->rlock_owner = tid;
_Py_atomic_store_ullong_relaxed(&self->rlock_owner, tid);
self->rlock_count = 1;
}
else if (r == PY_LOCK_INTR) {
Expand Down Expand Up @@ -525,13 +534,13 @@ rlock_release(rlockobject *self, PyObject *Py_UNUSED(ignored))
{
PyThread_ident_t tid = PyThread_get_thread_ident_ex();

if (self->rlock_count == 0 || self->rlock_owner != tid) {
if (!rlock_is_owned_by(self, tid)) {
PyErr_SetString(PyExc_RuntimeError,
"cannot release un-acquired lock");
return NULL;
}
if (--self->rlock_count == 0) {
self->rlock_owner = 0;
_Py_atomic_store_ullong_relaxed(&self->rlock_owner, 0);
PyThread_release_lock(self->rlock_lock);
}
Py_RETURN_NONE;
Expand Down Expand Up @@ -570,7 +579,7 @@ rlock_acquire_restore(rlockobject *self, PyObject *args)
return NULL;
}
assert(self->rlock_count == 0);
self->rlock_owner = owner;
_Py_atomic_store_ullong_relaxed(&self->rlock_owner, owner);
self->rlock_count = count;
Py_RETURN_NONE;
}
Expand All @@ -595,7 +604,7 @@ rlock_release_save(rlockobject *self, PyObject *Py_UNUSED(ignored))
owner = self->rlock_owner;
count = self->rlock_count;
self->rlock_count = 0;
self->rlock_owner = 0;
_Py_atomic_store_ullong_relaxed(&self->rlock_owner, 0);
PyThread_release_lock(self->rlock_lock);
return Py_BuildValue("k" Py_PARSE_THREAD_IDENT_T, count, owner);
}
Expand All @@ -609,8 +618,9 @@ static PyObject *
rlock_recursion_count(rlockobject *self, PyObject *Py_UNUSED(ignored))
{
PyThread_ident_t tid = PyThread_get_thread_ident_ex();
return PyLong_FromUnsignedLong(
self->rlock_owner == tid ? self->rlock_count : 0UL);
PyThread_ident_t owner =
_Py_atomic_load_ullong_relaxed(&self->rlock_owner);
return PyLong_FromUnsignedLong(owner == tid ? self->rlock_count : 0UL);
}

PyDoc_STRVAR(rlock_recursion_count_doc,
Expand All @@ -623,7 +633,7 @@ rlock_is_owned(rlockobject *self, PyObject *Py_UNUSED(ignored))
{
PyThread_ident_t tid = PyThread_get_thread_ident_ex();

if (self->rlock_count > 0 && self->rlock_owner == tid) {
if (rlock_is_owned_by(self, tid)) {
Py_RETURN_TRUE;
}
Py_RETURN_FALSE;
Expand Down Expand Up @@ -657,10 +667,12 @@ rlock_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
static PyObject *
rlock_repr(rlockobject *self)
{
PyThread_ident_t owner =
_Py_atomic_load_ullong_relaxed(&self->rlock_owner);
return PyUnicode_FromFormat(
"<%s %s object owner=%" PY_FORMAT_THREAD_IDENT_T " count=%lu at %p>",
self->rlock_count ? "locked" : "unlocked",
Py_TYPE(self)->tp_name, self->rlock_owner,
Py_TYPE(self)->tp_name, owner,
self->rlock_count, self);
}

Expand Down