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

The ID of the owning thread (`rlock_owner`) may be accessed by
multiple threads without holding the underlying lock; relaxed
atomics are used in place of the previous loads/stores.

The number of times that the lock has been acquired (`rlock_count`)
is only ever accessed by the thread that holds the lock; we do not
need to use atomics to access it.

1 files changed, 14 insertions, 0 deletions

diff --git a/Include/cpython/pyatomic_msc.h b/Include/cpython/pyatomic_msc.h
index b5c1ec9..6ab6401 100644
--- a/Include/cpython/pyatomic_msc.h
+++ b/Include/cpython/pyatomic_msc.h
@@ -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 ------------------------------------------------------
 
@@ -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 *