------------------------------------------------------------------------------ -- -- -- 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 -- -- . -- -- -- -- 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;