MdePkg/Library/BaseSynchronizationLib/Ia32/InterlockedCompareExchange32.c

   1 /** @file
   2   InterlockedCompareExchange32 function
   3
   4   Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
   5   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 /**
  10   Performs an atomic compare exchange operation on a 32-bit unsigned integer.
  11
  12   Performs an atomic compare exchange operation on the 32-bit unsigned integer
  13   specified by Value.  If Value is equal to CompareValue, then Value is set to
  14   ExchangeValue and CompareValue is returned.  If Value is not equal to CompareValue,
  15   then Value is returned.  The compare exchange operation must be performed using
  16   MP safe mechanisms.
  17
  18   @param  Value         A pointer to the 32-bit value for the compare exchange
  19                         operation.
  20   @param  CompareValue  32-bit value used in compare operation.
  21   @param  ExchangeValue 32-bit value used in exchange operation.
  22
  23   @return The original *Value before exchange.
  24
  25 **/
  26 UINT32
  27 EFIAPI
  28 InternalSyncCompareExchange32 (
  29   IN      volatile UINT32  *Value,
  30   IN      UINT32           CompareValue,
  31   IN      UINT32           ExchangeValue
  32   )
  33 {
  34   _asm {
  35     mov     ecx, Value
  36     mov     eax, CompareValue
  37     mov     edx, ExchangeValue
  38     lock    cmpxchg [ecx], edx
  39   }
  40 }