MdePkg/Library/BaseLib/Ia32/InterlockedDecrement.c

   1 /** @file
   2   InterlockedDecrement function
   3
   4   Copyright (c) 2006 - 2008, 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
  17
  18 /**
  19   Performs an atomic decrement of an 32-bit unsigned integer.
  20
  21   Performs an atomic decrement of the 32-bit unsigned integer specified by
  22   Value and returns the decrement value. The decrement operation must be
  23   performed using MP safe mechanisms. The state of the return value is not
  24   guaranteed to be MP safe.
  25
  26   @param  Value A pointer to the 32-bit value to decrement.
  27
  28   @return The decrement value.
  29
  30 **/
  31 UINT32
  32 EFIAPI
  33 InternalSyncDecrement (
  34   IN      UINT32                    *Value
  35   )
  36 {
  37   _asm {
  38     mov     eax, Value
  39     lock    dec     dword ptr [eax]
  40     mov     eax, [eax]
  41   }
  42 }