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.

4 files changed, 46 insertions, 0 deletions

diff --git a/Include/cpython/pyatomic.h b/Include/cpython/pyatomic.h
index e10d482..9b57741 100644
--- a/Include/cpython/pyatomic.h
+++ b/Include/cpython/pyatomic.h
@@ -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)
@@ -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 ------------
 
diff --git a/Include/cpython/pyatomic_gcc.h b/Include/cpython/pyatomic_gcc.h
index 4095e18..bc74149 100644
--- a/Include/cpython/pyatomic_gcc.h
+++ b/Include/cpython/pyatomic_gcc.h
@@ -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 ------------------------------------------------------
 
@@ -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 ------------
 
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 *
diff --git a/Include/cpython/pyatomic_std.h b/Include/cpython/pyatomic_std.h
index 6c934a2..d3004db 100644
--- a/Include/cpython/pyatomic_std.h
+++ b/Include/cpython/pyatomic_std.h
@@ -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 ------------------------------------------------------
 
@@ -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 ------------