MdePkg/BaseSynchronizationLib: Add volatile Interlocked*() APIs

[mirror_edk2.git] / MdePkg / Library / BaseSynchronizationLib / Ia32 / InterlockedDecrement.c

/** @file\r
  InterlockedDecrement function\r
\r
  Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>\r
  This program and the accompanying materials\r
  are licensed and made available under the terms and conditions of the BSD License\r
  which accompanies this distribution.  The full text of the license may be found at\r
  http://opensource.org/licenses/bsd-license.php.\r
\r
  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
\r
**/\r
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/**\r
  Performs an atomic decrement of an 32-bit unsigned integer.\r
\r
  Performs an atomic decrement of the 32-bit unsigned integer specified by\r
  Value and returns the decrement value. The decrement operation must be\r
  performed using MP safe mechanisms. The state of the return value is not\r
  guaranteed to be MP safe.\r
\r
  @param  Value A pointer to the 32-bit value to decrement.\r
\r
  @return The decrement value.\r
\r
**/\r
UINT32\r
EFIAPI\r
InternalSyncDecrement (\r
  IN      volatile UINT32           *Value\r
  )\r
{\r
  _asm {\r
    mov     eax, Value\r
    lock    dec     dword ptr [eax]\r
    mov     eax, [eax]\r
  }\r
}\r