EdkCompatibilityPkg/Foundation/Library/Dxe/EfiDriverLib/Lock.c

   1 /*++
   2
   3 Copyright (c) 2004, Intel Corporation
   4 All rights reserved. This program and the accompanying materials
   5 are licensed and made available under the terms and conditions of the BSD License
   6 which accompanies this distribution.  The full text of the license may be found at
   7 http://opensource.org/licenses/bsd-license.php
   8
   9 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  10 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  11
  12 Module Name:
  13
  14   Lock.c
  15
  16 Abstract:
  17
  18   Support for locking lib services.
  19
  20 --*/
  21
  22 #include "Tiano.h"
  23 #include "EfiDriverLib.h"
  24
  25 VOID
  26 EfiInitializeLock (
  27   IN OUT EFI_LOCK *Lock,
  28   IN EFI_TPL      Priority
  29   )
  30 /*++
  31
  32 Routine Description:
  33
  34   Initialize a basic mutual exclusion lock.   Each lock
  35   provides mutual exclusion access at it's task priority
  36   level.  Since there is no-premption (at any TPL) or
  37   multiprocessor support, acquiring the lock only consists
  38   of raising to the locks TPL.
  39
  40   Note on a check build ASSERT()s are used to ensure proper
  41   lock usage.
  42
  43 Arguments:
  44
  45   Lock        - The EFI_LOCK structure to initialize
  46
  47   Priority    - The task priority level of the lock
  48
  49
  50 Returns:
  51
  52   An initialized Efi Lock structure.
  53
  54 --*/
  55 {
  56   Lock->Tpl       = Priority;
  57   Lock->OwnerTpl  = 0;
  58   Lock->Lock      = 0;
  59 }
  60
  61 EFI_STATUS
  62 EfiAcquireLockOrFail (
  63   IN EFI_LOCK  *Lock
  64   )
  65 /*++
  66
  67 Routine Description:
  68
  69   Initialize a basic mutual exclusion lock.   Each lock
  70   provides mutual exclusion access at it's task priority
  71   level.  Since there is no-premption (at any TPL) or
  72   multiprocessor support, acquiring the lock only consists
  73   of raising to the locks TPL.
  74
  75 Arguments:
  76
  77   Lock        - The EFI_LOCK structure to initialize
  78
  79 Returns:
  80
  81   EFI_SUCCESS       - Lock Owned.
  82   EFI_ACCESS_DENIED - Reentrant Lock Acquisition, Lock not Owned.
  83
  84 --*/
  85 {
  86   if (Lock->Lock != 0) {
  87     //
  88     // Lock is already owned, so bail out
  89     //
  90     return EFI_ACCESS_DENIED;
  91   }
  92
  93   Lock->OwnerTpl = gBS->RaiseTPL (Lock->Tpl);
  94
  95   Lock->Lock += 1;
  96   return EFI_SUCCESS;
  97 }
  98
  99 VOID
 100 EfiAcquireLock (
 101   IN EFI_LOCK  *Lock
 102   )
 103 /*++
 104
 105 Routine Description:
 106
 107   Raising to the task priority level of the mutual exclusion
 108   lock, and then acquires ownership of the lock.
 109
 110 Arguments:
 111
 112   Lock - The lock to acquire
 113
 114 Returns:
 115
 116   Lock owned
 117
 118 --*/
 119 {
 120   EFI_STATUS  Status;
 121
 122   Status = EfiAcquireLockOrFail (Lock);
 123
 124   //
 125   // Lock was already locked.
 126   //
 127   ASSERT_EFI_ERROR (Status);
 128 }
 129
 130 VOID
 131 EfiReleaseLock (
 132   IN EFI_LOCK  *Lock
 133   )
 134 /*++
 135
 136 Routine Description:
 137
 138     Releases ownership of the mutual exclusion lock, and
 139     restores the previous task priority level.
 140
 141 Arguments:
 142
 143     Lock - The lock to release
 144
 145 Returns:
 146
 147     Lock unowned
 148
 149 --*/
 150 {
 151   EFI_TPL Tpl;
 152
 153   Tpl = Lock->OwnerTpl;
 154
 155   ASSERT (Lock->Lock == 1);
 156   Lock->Lock -= 1;
 157
 158   gBS->RestoreTPL (Tpl);
 159 }