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
  11
  12 /**
  13   Performs an atomic compare exchange operation on a 32-bit unsigned integer.
  14
  15   Performs an atomic compare exchange operation on the 32-bit unsigned integer
  16   specified by Value.  If Value is equal to CompareValue, then Value is set to
  17   ExchangeValue and CompareValue is returned.  If Value is not equal to CompareValue,
  18   then Value is returned.  The compare exchange operation must be performed using
  19   MP safe mechanisms.
  20
  21   @param  Value         A pointer to the 32-bit value for the compare exchange
  22                         operation.
  23   @param  CompareValue  32-bit value used in compare operation.
  24   @param  ExchangeValue 32-bit value used in exchange operation.
  25
  26   @return The original *Value before exchange.
  27
  28 **/
  29 UINT32
  30 EFIAPI
  31 InternalSyncCompareExchange32 (
  32   IN      volatile UINT32           *Value,
  33   IN      UINT32                    CompareValue,
  34   IN      UINT32                    ExchangeValue
  35   )
  36 {
  37   _asm {
  38     mov     ecx, Value
  39     mov     eax, CompareValue
  40     mov     edx, ExchangeValue
  41     lock    cmpxchg [ecx], edx
  42   }
  43 }
  44