MdeModulePkg/Core/Dxe/Library/Library.c

   1 /** @file
   2   DXE Core library services.
   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 #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