------------------------------------------------------------------------------ -- -- -- 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) 2012-2019, 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. package System.Atomic_Primitives is pragma Preelaborate; 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 -- ------------------------------------ function Atomic_Load_8 (Ptr : Address; Model : Mem_Model := Seq_Cst) return uint8; pragma Import (Intrinsic, Atomic_Load_8, "__atomic_load_1"); function Atomic_Load_16 (Ptr : Address; Model : Mem_Model := Seq_Cst) return uint16; pragma Import (Intrinsic, Atomic_Load_16, "__atomic_load_2"); function Atomic_Load_32 (Ptr : Address; Model : Mem_Model := Seq_Cst) return uint32; pragma Import (Intrinsic, Atomic_Load_32, "__atomic_load_4"); function Atomic_Load_64 (Ptr : Address; Model : Mem_Model := Seq_Cst) return uint64; pragma Import (Intrinsic, Atomic_Load_64, "__atomic_load_8"); function Sync_Compare_And_Swap_8 (Ptr : Address; Expected : uint8; Desired : uint8) return uint8; pragma Import (Intrinsic, Sync_Compare_And_Swap_8, "__sync_val_compare_and_swap_1"); function Sync_Compare_And_Swap_16 (Ptr : Address; Expected : uint16; Desired : uint16) return uint16; pragma Import (Intrinsic, Sync_Compare_And_Swap_16, "__sync_val_compare_and_swap_2"); function Sync_Compare_And_Swap_32 (Ptr : Address; Expected : uint32; Desired : uint32) return uint32; pragma Import (Intrinsic, Sync_Compare_And_Swap_32, "__sync_val_compare_and_swap_4"); function Sync_Compare_And_Swap_64 (Ptr : Address; Expected : uint64; Desired : uint64) return uint64; pragma Import (Intrinsic, Sync_Compare_And_Swap_64, "__sync_val_compare_and_swap_8"); -- ??? We might want to switch to the __atomic series of builtins for -- compare-and-swap operations at some point. -- function Atomic_Compare_Exchange_8 -- (Ptr : Address; -- Expected : Address; -- Desired : uint8; -- Weak : Boolean := False; -- Success_Model : Mem_Model := Seq_Cst; -- Failure_Model : Mem_Model := Seq_Cst) return Boolean; -- pragma Import (Intrinsic, -- Atomic_Compare_Exchange_8, -- "__atomic_compare_exchange_1"); -------------------------- -- Lock-free operations -- -------------------------- -- The lock-free implementation uses two atomic instructions for the -- expansion of protected operations: -- * Lock_Free_Read_N atomically loads the value of the protected component -- accessed by the current protected operation. -- * Lock_Free_Try_Write_N tries to write the Desired value into Ptr only -- if Expected and Desired mismatch. function Lock_Free_Read_8 (Ptr : Address) return uint8; function Lock_Free_Read_16 (Ptr : Address) return uint16; function Lock_Free_Read_32 (Ptr : Address) return uint32; function Lock_Free_Read_64 (Ptr : Address) return uint64; function Lock_Free_Try_Write_8 (Ptr : Address; Expected : in out uint8; Desired : uint8) return Boolean; function Lock_Free_Try_Write_16 (Ptr : Address; Expected : in out uint16; Desired : uint16) return Boolean; function Lock_Free_Try_Write_32 (Ptr : Address; Expected : in out uint32; Desired : uint32) return Boolean; function Lock_Free_Try_Write_64 (Ptr : Address; Expected : in out uint64; Desired : uint64) return Boolean; pragma Inline (Lock_Free_Read_8); pragma Inline (Lock_Free_Read_16); pragma Inline (Lock_Free_Read_32); pragma Inline (Lock_Free_Read_64); pragma Inline (Lock_Free_Try_Write_8); pragma Inline (Lock_Free_Try_Write_16); pragma Inline (Lock_Free_Try_Write_32); pragma Inline (Lock_Free_Try_Write_64); end System.Atomic_Primitives;