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      1 /** @file
      2   DXE Core library services.
      3 
      4 Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
      5 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 #include "DxeMain.h"
     16 
     17 //
     18 // Lock Stuff
     19 //
     20 /**
     21   Initialize a basic mutual exclusion lock.   Each lock
     22   provides mutual exclusion access at it's task priority
     23   level.  Since there is no-premption (at any TPL) or
     24   multiprocessor support, acquiring the lock only consists
     25   of raising to the locks TPL.
     26 
     27   @param  Lock               The EFI_LOCK structure to initialize
     28 
     29   @retval EFI_SUCCESS        Lock Owned.
     30   @retval EFI_ACCESS_DENIED  Reentrant Lock Acquisition, Lock not Owned.
     31 
     32 **/
     33 EFI_STATUS
     34 CoreAcquireLockOrFail (
     35   IN EFI_LOCK  *Lock
     36   )
     37 {
     38   ASSERT (Lock != NULL);
     39   ASSERT (Lock->Lock != EfiLockUninitialized);
     40 
     41   if (Lock->Lock == EfiLockAcquired) {
     42     //
     43     // Lock is already owned, so bail out
     44     //
     45     return EFI_ACCESS_DENIED;
     46   }
     47 
     48   Lock->OwnerTpl = CoreRaiseTpl (Lock->Tpl);
     49 
     50   Lock->Lock = EfiLockAcquired;
     51   return EFI_SUCCESS;
     52 }
     53 
     54 
     55 
     56 /**
     57   Raising to the task priority level of the mutual exclusion
     58   lock, and then acquires ownership of the lock.
     59 
     60   @param  Lock               The lock to acquire
     61 
     62   @return Lock owned
     63 
     64 **/
     65 VOID
     66 CoreAcquireLock (
     67   IN EFI_LOCK  *Lock
     68   )
     69 {
     70   ASSERT (Lock != NULL);
     71   ASSERT (Lock->Lock == EfiLockReleased);
     72 
     73   Lock->OwnerTpl = CoreRaiseTpl (Lock->Tpl);
     74   Lock->Lock     = EfiLockAcquired;
     75 }
     76 
     77 
     78 
     79 /**
     80   Releases ownership of the mutual exclusion lock, and
     81   restores the previous task priority level.
     82 
     83   @param  Lock               The lock to release
     84 
     85   @return Lock unowned
     86 
     87 **/
     88 VOID
     89 CoreReleaseLock (
     90   IN EFI_LOCK  *Lock
     91   )
     92 {
     93   EFI_TPL Tpl;
     94 
     95   ASSERT (Lock != NULL);
     96   ASSERT (Lock->Lock == EfiLockAcquired);
     97 
     98   Tpl = Lock->OwnerTpl;
     99 
    100   Lock->Lock = EfiLockReleased;
    101 
    102   CoreRestoreTpl (Tpl);
    103 }
    104 
    105 
    106 
    107