gh-116738: Make _csv module thread-safe

Include/cpython/pyatomic.h

@@ -275,6 +275,9 @@ _Py_atomic_or_uintptr(uintptr_t *obj, uintptr_t value);
 static inline int
 _Py_atomic_load_int(const int *obj);
 
+static inline long
+_Py_atomic_load_long(const long *obj);
+
 static inline int8_t
 _Py_atomic_load_int8(const int8_t *obj);
 
@@ -369,6 +372,9 @@ _Py_atomic_load_ullong_relaxed(const unsigned long long *obj);
 static inline void
 _Py_atomic_store_int(int *obj, int value);
 
+static inline void
+_Py_atomic_store_long(long *obj, long value);
+
 static inline void
 _Py_atomic_store_int8(int8_t *obj, int8_t value);
 

Include/cpython/pyatomic_gcc.h

@@ -247,6 +247,10 @@ static inline int
 _Py_atomic_load_int(const int *obj)
 { return __atomic_load_n(obj, __ATOMIC_SEQ_CST); }
 
+static inline long
+_Py_atomic_load_long(const long *obj)
+{ return __atomic_load_n(obj, __ATOMIC_SEQ_CST); }
+
 static inline int8_t
 _Py_atomic_load_int8(const int8_t *obj)
 { return __atomic_load_n(obj, __ATOMIC_SEQ_CST); }
@@ -369,6 +373,10 @@ static inline void
 _Py_atomic_store_int(int *obj, int value)
 { __atomic_store_n(obj, value, __ATOMIC_SEQ_CST); }
 
+static inline void
+_Py_atomic_store_long(long *obj, long value)
+{ __atomic_store_n(obj, value, __ATOMIC_SEQ_CST); }
+
 static inline void
 _Py_atomic_store_int8(int8_t *obj, int8_t value)
 { __atomic_store_n(obj, value, __ATOMIC_SEQ_CST); }

Include/cpython/pyatomic_msc.h

@@ -355,6 +355,14 @@ _Py_atomic_exchange_int(int *obj, int value)
                                            (int32_t)value);
 }
 
+static inline int
+_Py_atomic_exchange_long(long *obj, long value)
+{
+    _Py_atomic_ASSERT_ARG_TYPE(int32_t);
+    return (int)_Py_atomic_exchange_int32((int32_t *)obj,
+                                          (int32_t)value);
+}
+
 static inline unsigned int
 _Py_atomic_exchange_uint(unsigned int *obj, unsigned int value)
 {
@@ -581,6 +589,13 @@ _Py_atomic_load_int(const int *obj)
     return (int)_Py_atomic_load_uint32((uint32_t *)obj);
 }
 
+static inline long
+_Py_atomic_load_long(const long *obj)
+{
+    _Py_atomic_ASSERT_ARG_TYPE(uint32_t);
+    return (int)_Py_atomic_load_uint32((uint32_t *)obj);
+}
+
 static inline unsigned int
 _Py_atomic_load_uint(const unsigned int *obj)
 {
@@ -727,6 +742,12 @@ _Py_atomic_store_int(int *obj, int value)
     (void)_Py_atomic_exchange_int(obj, value);
 }
 
+static inline void
+_Py_atomic_store_long(long *obj, long value)
+{
+    (void)_Py_atomic_exchange_long(obj, value);
+}
+
 static inline void
 _Py_atomic_store_int8(int8_t *obj, int8_t value)
 {

Include/cpython/pyatomic_std.h

@@ -413,6 +413,13 @@ _Py_atomic_load_int(const int *obj)
     return atomic_load((const _Atomic(int)*)obj);
 }
 
+static inline long
+_Py_atomic_load_long(const long *obj)
+{
+    _Py_USING_STD;
+    return atomic_load((const _Atomic(long)*)obj);
+}
+
 static inline int8_t
 _Py_atomic_load_int8(const int8_t *obj)
 {
@@ -637,6 +644,13 @@ _Py_atomic_store_int(int *obj, int value)
     atomic_store((_Atomic(int)*)obj, value);
 }
 
+static inline void
+_Py_atomic_store_long(long *obj, long value)
+{
+    _Py_USING_STD;
+    atomic_store((_Atomic(long)*)obj, value);
+}
+
 static inline void
 _Py_atomic_store_int8(int8_t *obj, int8_t value)
 {

Include/internal/pycore_pyatomic_ft_wrappers.h

@@ -55,6 +55,9 @@ extern "C" {
     _Py_atomic_store_ssize_relaxed(&value, new_value)
 #define FT_ATOMIC_STORE_UINT8_RELAXED(value, new_value) \
     _Py_atomic_store_uint8_relaxed(&value, new_value)
+#define FT_ATOMIC_LOAD_LONG(value) _Py_atomic_load_long(&value)
+#define FT_ATOMIC_STORE_LONG(value, new_value) \
+    _Py_atomic_store_long(&value, new_value)
 #define FT_ATOMIC_STORE_UINT16_RELAXED(value, new_value) \
     _Py_atomic_store_uint16_relaxed(&value, new_value)
 #define FT_ATOMIC_STORE_UINT32_RELAXED(value, new_value) \
@@ -80,6 +83,8 @@ extern "C" {
 #define FT_ATOMIC_STORE_UINTPTR_RELEASE(value, new_value) value = new_value
 #define FT_ATOMIC_STORE_SSIZE_RELAXED(value, new_value) value = new_value
 #define FT_ATOMIC_STORE_UINT8_RELAXED(value, new_value) value = new_value
+#define FT_ATOMIC_LOAD_LONG(value) value
+#define FT_ATOMIC_STORE_LONG(value, new_value) value = new_value
 #define FT_ATOMIC_STORE_UINT16_RELAXED(value, new_value) value = new_value
 #define FT_ATOMIC_STORE_UINT32_RELAXED(value, new_value) value = new_value
 

Modules/_csv.c

@@ -14,6 +14,7 @@ module instead.
 #endif
 
 #include "Python.h"
+#include "pycore_pyatomic_ft_wrappers.h"
 
 #include <stddef.h>               // offsetof()
 #include <stdbool.h>
@@ -702,10 +703,11 @@ parse_grow_buff(ReaderObj *self)
 static int
 parse_add_char(ReaderObj *self, _csvstate *module_state, Py_UCS4 c)
 {
-    if (self->field_len >= module_state->field_limit) {
+    long field_limit = FT_ATOMIC_LOAD_LONG(module_state->field_limit);
+    if (self->field_len >= field_limit) {
         PyErr_Format(module_state->error_obj,
                      "field larger than field limit (%ld)",
-                     module_state->field_limit);
+                     field_limit);
         return -1;
     }
     if (self->field_len == self->field_size && !parse_grow_buff(self))
@@ -1652,18 +1654,18 @@ _csv_field_size_limit_impl(PyObject *module, PyObject *new_limit)
 /*[clinic end generated code: output=f2799ecd908e250b input=cec70e9226406435]*/
 {
     _csvstate *module_state = get_csv_state(module);
-    long old_limit = module_state->field_limit;
+    long old_limit = FT_ATOMIC_LOAD_LONG(module_state->field_limit);
     if (new_limit != NULL) {
         if (!PyLong_CheckExact(new_limit)) {
             PyErr_Format(PyExc_TypeError,
                          "limit must be an integer");
             return NULL;
         }
-        module_state->field_limit = PyLong_AsLong(new_limit);
-        if (module_state->field_limit == -1 && PyErr_Occurred()) {
-            module_state->field_limit = old_limit;
+        long new_limit_value = PyLong_AsLong(new_limit);
+        if (new_limit_value == -1 && PyErr_Occurred()) {
             return NULL;
         }
+        FT_ATOMIC_STORE_LONG(module_state->field_limit, new_limit_value);
     }
     return PyLong_FromLong(old_limit);
 }