| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT RUN-TIME COMPONENTS -- |
| -- -- |
| -- S Y S T E M . A T O M I C _ P R I M I T I V E S -- |
| -- -- |
| -- S p e c -- |
| -- -- |
| -- Copyright (C) 2012-2022, Free Software Foundation, Inc. -- |
| -- -- |
| -- GNAT is free software; you can redistribute it and/or modify it under -- |
| -- terms of the GNU General Public License as published by the Free Soft- -- |
| -- ware Foundation; either version 3, or (at your option) any later ver- -- |
| -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- |
| -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- |
| -- or FITNESS FOR A PARTICULAR PURPOSE. -- |
| -- -- |
| -- As a special exception under Section 7 of GPL version 3, you are granted -- |
| -- additional permissions described in the GCC Runtime Library Exception, -- |
| -- version 3.1, as published by the Free Software Foundation. -- |
| -- -- |
| -- You should have received a copy of the GNU General Public License and -- |
| -- a copy of the GCC Runtime Library Exception along with this program; -- |
| -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- |
| -- <http://www.gnu.org/licenses/>. -- |
| -- -- |
| -- GNAT was originally developed by the GNAT team at New York University. -- |
| -- Extensive contributions were provided by Ada Core Technologies Inc. -- |
| -- -- |
| ------------------------------------------------------------------------------ |
| |
| -- This package contains both atomic primitives defined from GCC built-in |
| -- functions and operations used by the compiler to generate the lock-free |
| -- implementation of protected objects. |
| |
| with Interfaces.C; |
| |
| package System.Atomic_Primitives is |
| pragma Pure; |
| |
| type uint is mod 2 ** Long_Integer'Size; |
| |
| type uint8 is mod 2**8 |
| with Size => 8; |
| |
| type uint16 is mod 2**16 |
| with Size => 16; |
| |
| type uint32 is mod 2**32 |
| with Size => 32; |
| |
| type uint64 is mod 2**64 |
| with Size => 64; |
| |
| Relaxed : constant := 0; |
| Consume : constant := 1; |
| Acquire : constant := 2; |
| Release : constant := 3; |
| Acq_Rel : constant := 4; |
| Seq_Cst : constant := 5; |
| Last : constant := 6; |
| |
| subtype Mem_Model is Integer range Relaxed .. Last; |
| |
| ------------------------------------ |
| -- GCC built-in atomic primitives -- |
| ------------------------------------ |
| |
| generic |
| type Atomic_Type is mod <>; |
| function Atomic_Load |
| (Ptr : Address; |
| Model : Mem_Model := Seq_Cst) return Atomic_Type; |
| pragma Import (Intrinsic, Atomic_Load, "__atomic_load_n"); |
| |
| function Atomic_Load_8 is new Atomic_Load (uint8); |
| function Atomic_Load_16 is new Atomic_Load (uint16); |
| function Atomic_Load_32 is new Atomic_Load (uint32); |
| function Atomic_Load_64 is new Atomic_Load (uint64); |
| |
| generic |
| type Atomic_Type is mod <>; |
| function Atomic_Compare_Exchange |
| (Ptr : Address; |
| Expected : Address; |
| Desired : Atomic_Type; |
| Weak : Boolean := False; |
| Success_Model : Mem_Model := Seq_Cst; |
| Failure_Model : Mem_Model := Seq_Cst) return Boolean; |
| pragma Import |
| (Intrinsic, Atomic_Compare_Exchange, "__atomic_compare_exchange_n"); |
| |
| function Atomic_Compare_Exchange_8 is new Atomic_Compare_Exchange (uint8); |
| function Atomic_Compare_Exchange_16 is new Atomic_Compare_Exchange (uint16); |
| function Atomic_Compare_Exchange_32 is new Atomic_Compare_Exchange (uint32); |
| function Atomic_Compare_Exchange_64 is new Atomic_Compare_Exchange (uint64); |
| |
| function Atomic_Test_And_Set |
| (Ptr : System.Address; |
| Model : Mem_Model := Seq_Cst) return Boolean; |
| pragma Import (Intrinsic, Atomic_Test_And_Set, "__atomic_test_and_set"); |
| |
| procedure Atomic_Clear |
| (Ptr : System.Address; |
| Model : Mem_Model := Seq_Cst); |
| pragma Import (Intrinsic, Atomic_Clear, "__atomic_clear"); |
| |
| function Atomic_Always_Lock_Free |
| (Size : Interfaces.C.size_t; |
| Ptr : System.Address := System.Null_Address) return Boolean; |
| pragma Import |
| (Intrinsic, Atomic_Always_Lock_Free, "__atomic_always_lock_free"); |
| |
| -------------------------- |
| -- Lock-free operations -- |
| -------------------------- |
| |
| -- The lock-free implementation uses two atomic instructions for the |
| -- expansion of protected operations: |
| |
| -- * Lock_Free_Read atomically loads the value contained in Ptr (with the |
| -- Acquire synchronization mode). |
| |
| -- * Lock_Free_Try_Write atomically tries to write the Desired value into |
| -- Ptr if Ptr contains the Expected value. It returns true if the value |
| -- in Ptr was changed, or False if it was not, in which case Expected is |
| -- updated to the unexpected value in Ptr. Note that it does nothing and |
| -- returns true if Desired and Expected are equal. |
| |
| generic |
| type Atomic_Type is mod <>; |
| function Lock_Free_Read (Ptr : Address) return Atomic_Type; |
| |
| function Lock_Free_Read_8 is new Lock_Free_Read (uint8); |
| function Lock_Free_Read_16 is new Lock_Free_Read (uint16); |
| function Lock_Free_Read_32 is new Lock_Free_Read (uint32); |
| function Lock_Free_Read_64 is new Lock_Free_Read (uint64); |
| |
| generic |
| type Atomic_Type is mod <>; |
| function Lock_Free_Try_Write |
| (Ptr : Address; |
| Expected : in out Atomic_Type; |
| Desired : Atomic_Type) return Boolean; |
| |
| function Lock_Free_Try_Write_8 is new Lock_Free_Try_Write (uint8); |
| function Lock_Free_Try_Write_16 is new Lock_Free_Try_Write (uint16); |
| function Lock_Free_Try_Write_32 is new Lock_Free_Try_Write (uint32); |
| function Lock_Free_Try_Write_64 is new Lock_Free_Try_Write (uint64); |
| |
| private |
| pragma Inline (Lock_Free_Read); |
| pragma Inline (Lock_Free_Try_Write); |
| end System.Atomic_Primitives; |
