diff options
| -rw-r--r-- | library/core/src/sync/atomic.rs | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/library/core/src/sync/atomic.rs b/library/core/src/sync/atomic.rs index 8de7d53f302..4fc455d06ed 100644 --- a/library/core/src/sync/atomic.rs +++ b/library/core/src/sync/atomic.rs @@ -464,6 +464,23 @@ impl AtomicBool { /// **Note:** This method is only available on platforms that support atomic /// operations on `u8`. /// + /// # Migrating to `compare_exchange` and `compare_exchange_weak` + /// + /// `compare_and_swap` is equivalent to `compare_exchange` with the following mapping for + /// memory orderings: + /// + /// Original | Success | Failure + /// -------- | ------- | ------- + /// Relaxed | Relaxed | Relaxed + /// Acquire | Acquire | Acquire + /// Release | Release | Relaxed + /// AcqRel | AcqRel | Acquire + /// SeqCst | SeqCst | SeqCst + /// + /// `compare_exchange_weak` is allowed to fail spuriously even when the comparison succeeds, + /// which allows the compiler to generate better assembly code when the compare and swap + /// is used in a loop. + /// /// # Examples /// /// ``` @@ -1070,6 +1087,23 @@ impl<T> AtomicPtr<T> { /// **Note:** This method is only available on platforms that support atomic /// operations on pointers. /// + /// # Migrating to `compare_exchange` and `compare_exchange_weak` + /// + /// `compare_and_swap` is equivalent to `compare_exchange` with the following mapping for + /// memory orderings: + /// + /// Original | Success | Failure + /// -------- | ------- | ------- + /// Relaxed | Relaxed | Relaxed + /// Acquire | Acquire | Acquire + /// Release | Release | Relaxed + /// AcqRel | AcqRel | Acquire + /// SeqCst | SeqCst | SeqCst + /// + /// `compare_exchange_weak` is allowed to fail spuriously even when the comparison succeeds, + /// which allows the compiler to generate better assembly code when the compare and swap + /// is used in a loop. + /// /// # Examples /// /// ``` @@ -1612,6 +1646,23 @@ happens, and using [`Release`] makes the load part [`Relaxed`]. **Note**: This method is only available on platforms that support atomic operations on [`", $s_int_type, "`](", $int_ref, "). +# Migrating to `compare_exchange` and `compare_exchange_weak` + +`compare_and_swap` is equivalent to `compare_exchange` with the following mapping for +memory orderings: + +Original | Success | Failure +-------- | ------- | ------- +Relaxed | Relaxed | Relaxed +Acquire | Acquire | Acquire +Release | Release | Relaxed +AcqRel | AcqRel | Acquire +SeqCst | SeqCst | SeqCst + +`compare_exchange_weak` is allowed to fail spuriously even when the comparison succeeds, +which allows the compiler to generate better assembly code when the compare and swap +is used in a loop. + # Examples ``` |