audk/MdeModulePkg/Core/Dxe/Library/Library.c

/** @file
  DXE Core library services.

Copyright (c) 2006 - 2008, Intel Corporation. <BR>
All rights reserved. This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution.  The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php

THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/

#include "DxeMain.h"

//
// Lock Stuff
//
/**
  Initialize a basic mutual exclusion lock.   Each lock
  provides mutual exclusion access at it's task priority
  level.  Since there is no-premption (at any TPL) or
  multiprocessor support, acquiring the lock only consists
  of raising to the locks TPL.

  @param  Lock               The EFI_LOCK structure to initialize

  @retval EFI_SUCCESS        Lock Owned.
  @retval EFI_ACCESS_DENIED  Reentrant Lock Acquisition, Lock not Owned.

**/
EFI_STATUS
CoreAcquireLockOrFail (
  IN EFI_LOCK  *Lock
  )
{
  ASSERT (Lock != NULL);
  ASSERT (Lock->Lock != EfiLockUninitialized);

  if (Lock->Lock == EfiLockAcquired) {
    //
    // Lock is already owned, so bail out
    //
    return EFI_ACCESS_DENIED;
  }

  Lock->OwnerTpl = CoreRaiseTpl (Lock->Tpl);

  Lock->Lock = EfiLockAcquired;
  return EFI_SUCCESS;
}



/**
  Raising to the task priority level of the mutual exclusion
  lock, and then acquires ownership of the lock.

  @param  Lock               The lock to acquire

  @return Lock owned

**/
VOID
CoreAcquireLock (
  IN EFI_LOCK  *Lock
  )
{
  ASSERT (Lock != NULL);
  ASSERT (Lock->Lock == EfiLockReleased);

  Lock->OwnerTpl = CoreRaiseTpl (Lock->Tpl);
  Lock->Lock     = EfiLockAcquired;
}



/**
  Releases ownership of the mutual exclusion lock, and
  restores the previous task priority level.

  @param  Lock               The lock to release

  @return Lock unowned

**/
VOID
CoreReleaseLock (
  IN EFI_LOCK  *Lock
  )
{
  EFI_TPL Tpl;

  ASSERT (Lock != NULL);
  ASSERT (Lock->Lock == EfiLockAcquired);

  Tpl = Lock->OwnerTpl;

  Lock->Lock = EfiLockReleased;

  CoreRestoreTpl (Tpl);
}