Auto merge of #102080 - yanchen4791:issue-99824-fix, r=cjgillot

[rust.git] / library / core / src / sync / atomic.rs

diff --git a/library/core/src/sync/atomic.rs b/library/core/src/sync/atomic.rs
index 3c96290fc537e19bbe1e2b400a5eabf13ece5a0c..cdc47e17938dc38e3e58e343f3015dd9a2545c11 100644 (file)
--- a/library/core/src/sync/atomic.rs
+++ b/library/core/src/sync/atomic.rs
@@ -955,6 +955,14 @@ pub fn as_mut_ptr(&self) -> *mut bool {
     /// **Note:** This method is only available on platforms that support atomic
     /// operations on `u8`.
     ///
+    /// # Considerations
+    ///
+    /// This method is not magic;  it is not provided by the hardware.
+    /// It is implemented in terms of [`AtomicBool::compare_exchange_weak`], and suffers from the same drawbacks.
+    /// In particular, this method will not circumvent the [ABA Problem].
+    ///
+    /// [ABA Problem]: https://en.wikipedia.org/wiki/ABA_problem
+    ///
     /// # Examples
     ///
     /// ```rust
@@ -1422,6 +1430,14 @@ pub fn compare_exchange_weak(
     /// **Note:** This method is only available on platforms that support atomic
     /// operations on pointers.
     ///
+    /// # Considerations
+    ///
+    /// This method is not magic;  it is not provided by the hardware.
+    /// It is implemented in terms of [`AtomicPtr::compare_exchange_weak`], and suffers from the same drawbacks.
+    /// In particular, this method will not circumvent the [ABA Problem].
+    ///
+    /// [ABA Problem]: https://en.wikipedia.org/wiki/ABA_problem
+    ///
     /// # Examples
     ///
     /// ```rust
@@ -1626,8 +1642,8 @@ pub fn fetch_byte_sub(&self, val: usize, order: Ordering) -> *mut T {
     /// and the argument `val`, and stores a pointer with provenance of the
     /// current pointer and the resulting address.
     ///
-    /// This is equivalent equivalent to using [`map_addr`] to atomically
-    /// perform `ptr = ptr.map_addr(|a| a | val)`. This can be used in tagged
+    /// This is equivalent to using [`map_addr`] to atomically perform
+    /// `ptr = ptr.map_addr(|a| a | val)`. This can be used in tagged
     /// pointer schemes to atomically set tag bits.
     ///
     /// **Caveat**: This operation returns the previous value. To compute the
@@ -1677,8 +1693,8 @@ pub fn fetch_or(&self, val: usize, order: Ordering) -> *mut T {
     /// pointer, and the argument `val`, and stores a pointer with provenance of
     /// the current pointer and the resulting address.
     ///
-    /// This is equivalent equivalent to using [`map_addr`] to atomically
-    /// perform `ptr = ptr.map_addr(|a| a & val)`. This can be used in tagged
+    /// This is equivalent to using [`map_addr`] to atomically perform
+    /// `ptr = ptr.map_addr(|a| a & val)`. This can be used in tagged
     /// pointer schemes to atomically unset tag bits.
     ///
     /// **Caveat**: This operation returns the previous value. To compute the
@@ -1727,8 +1743,8 @@ pub fn fetch_and(&self, val: usize, order: Ordering) -> *mut T {
     /// pointer, and the argument `val`, and stores a pointer with provenance of
     /// the current pointer and the resulting address.
     ///
-    /// This is equivalent equivalent to using [`map_addr`] to atomically
-    /// perform `ptr = ptr.map_addr(|a| a ^ val)`. This can be used in tagged
+    /// This is equivalent to using [`map_addr`] to atomically perform
+    /// `ptr = ptr.map_addr(|a| a ^ val)`. This can be used in tagged
     /// pointer schemes to atomically toggle tag bits.
     ///
     /// **Caveat**: This operation returns the previous value. To compute the
@@ -2510,6 +2526,16 @@ pub fn fetch_xor(&self, val: $int_type, order: Ordering) -> $int_type {
             /// **Note**: This method is only available on platforms that support atomic operations on
             #[doc = concat!("[`", $s_int_type, "`].")]
             ///
+            /// # Considerations
+            ///
+            /// This method is not magic;  it is not provided by the hardware.
+            /// It is implemented in terms of
+            #[doc = concat!("[`", stringify!($atomic_type), "::compare_exchange_weak`],")]
+            /// and suffers from the same drawbacks.
+            /// In particular, this method will not circumvent the [ABA Problem].
+            ///
+            /// [ABA Problem]: https://en.wikipedia.org/wiki/ABA_problem
+            ///
             /// # Examples
             ///
             /// ```rust