MdePkg/Library/BaseLib/Ia32/InterlockedDecrement.c

   1 /** @file
   2   InterlockedDecrement function
   3
   4   Copyright (c) 2006 - 2007, Intel Corporation<BR>
   5   All rights reserved. This program and the accompanying materials
   6   are licensed and made available under the terms and conditions of the BSD License
   7   which accompanies this distribution.  The full text of the license may be found at
   8   http://opensource.org/licenses/bsd-license.php
   9
  10   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 **/
  14
  15 //
  16 // Include common header file for this module.
  17 //
  18
  19
  20 /**
  21   Performs an atomic decrement of an 32-bit unsigned integer.
  22
  23   Performs an atomic decrement of the 32-bit unsigned integer specified by
  24   Value and returns the decrement value. The decrement operation must be
  25   performed using MP safe mechanisms. The state of the return value is not
  26   guaranteed to be MP safe.
  27
  28   @param  Value A pointer to the 32-bit value to decrement.
  29
  30   @return The decrement value.
  31
  32 **/
  33 UINT32
  34 EFIAPI
  35 InternalSyncDecrement (
  36   IN      UINT32                    *Value
  37   )
  38 {
  39   _asm {
  40     mov     eax, Value
  41     lock    dec     dword ptr [eax]
  42     mov     eax, [eax]
  43   }
  44 }