EdkModulePkg/Core/Dxe/Event/tpl.c

   1 /*++
   2
   3 Copyright (c) 2006, 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     tpl.c
  15
  16 Abstract:
  17
  18     Task priority function
  19
  20 --*/
  21
  22 #include <DxeMain.h>
  23
  24 STATIC
  25 VOID
  26 CoreSetInterruptState (
  27   IN BOOLEAN      Enable
  28   )
  29 /*++
  30
  31 Routine Description:
  32
  33   Set Interrupt State
  34
  35 Arguments:
  36
  37   Enable - The state of enable or disable interrupt
  38
  39 Returns:
  40
  41   None
  42
  43 --*/
  44
  45 {
  46   if (gCpu != NULL) {
  47     if (Enable) {
  48       gCpu->EnableInterrupt(gCpu);
  49     } else {
  50       gCpu->DisableInterrupt(gCpu);
  51     }
  52   }
  53 }
  54
  55 //
  56 // Return the highest set bit
  57 //
  58 UINTN
  59 CoreHighestSetBit (
  60   IN UINTN     Number
  61   )
  62 /*++
  63
  64 Routine Description:
  65
  66   Return the highest set bit
  67
  68 Arguments:
  69
  70   Number - The value to check
  71
  72 Returns:
  73
  74   Bit position of the highest set bit
  75
  76 --*/
  77 {
  78   UINTN   msb;
  79
  80   msb = 31;
  81   while ((msb > 0) && ((Number & (UINTN)(1 << msb)) == 0)) {
  82     msb--;
  83   }
  84
  85   return msb;
  86 }
  87
  88
  89
  90 EFI_TPL
  91 EFIAPI
  92 CoreRaiseTpl (
  93   IN EFI_TPL      NewTpl
  94   )
  95 /*++
  96
  97 Routine Description:
  98
  99   Raise the task priority level to the new level.
 100   High level is implemented by disabling processor interrupts.
 101
 102 Arguments:
 103
 104   NewTpl  - New task priority level
 105
 106 Returns:
 107
 108   The previous task priority level
 109
 110 --*/
 111 {
 112   EFI_TPL     OldTpl;
 113
 114   OldTpl = gEfiCurrentTpl;
 115   ASSERT (OldTpl <= NewTpl);
 116   ASSERT (VALID_TPL (NewTpl));
 117
 118   //
 119   // If raising to high level, disable interrupts
 120   //
 121   if (NewTpl >= EFI_TPL_HIGH_LEVEL  &&  OldTpl < EFI_TPL_HIGH_LEVEL) {
 122     CoreSetInterruptState (FALSE);
 123   }
 124
 125   //
 126   // Set the new value
 127   //
 128   gEfiCurrentTpl = NewTpl;
 129
 130   return OldTpl;
 131 }
 132
 133
 134
 135 VOID
 136 EFIAPI
 137 CoreRestoreTpl (
 138   IN EFI_TPL NewTpl
 139   )
 140 /*++
 141
 142 Routine Description:
 143
 144   Lowers the task priority to the previous value.   If the new
 145   priority unmasks events at a higher priority, they are dispatched.
 146
 147 Arguments:
 148
 149   NewTpl  - New, lower, task priority
 150
 151 Returns:
 152
 153   None
 154
 155 --*/
 156 {
 157   EFI_TPL     OldTpl;
 158
 159   OldTpl = gEfiCurrentTpl;
 160   ASSERT (NewTpl <= OldTpl);
 161   ASSERT (VALID_TPL (NewTpl));
 162
 163   //
 164   // If lowering below HIGH_LEVEL, make sure
 165   // interrupts are enabled
 166   //
 167
 168   if (OldTpl >= EFI_TPL_HIGH_LEVEL  &&  NewTpl < EFI_TPL_HIGH_LEVEL) {
 169     gEfiCurrentTpl = EFI_TPL_HIGH_LEVEL;
 170   }
 171
 172   //
 173   // Dispatch any pending events
 174   //
 175
 176   while ((-2 << NewTpl) & gEventPending) {
 177     gEfiCurrentTpl = CoreHighestSetBit (gEventPending);
 178     if (gEfiCurrentTpl < EFI_TPL_HIGH_LEVEL) {
 179       CoreSetInterruptState (TRUE);
 180     }
 181     CoreDispatchEventNotifies (gEfiCurrentTpl);
 182   }
 183
 184   //
 185   // Set the new value
 186   //
 187
 188   gEfiCurrentTpl = NewTpl;
 189
 190   //
 191   // If lowering below HIGH_LEVEL, make sure
 192   // interrupts are enabled
 193   //
 194   if (gEfiCurrentTpl < EFI_TPL_HIGH_LEVEL) {
 195     CoreSetInterruptState (TRUE);
 196   }
 197
 198 }