MdeModulePkg/Core/Dxe/Event/tpl.c

   1 /** @file
   2
   3   Task priority (TPL) function
   4
   5 Copyright (c) 2006 - 2008, Intel Corporation
   6 All rights reserved. This program and the accompanying materials
   7 are licensed and made available under the terms and conditions of the BSD License
   8 which accompanies this distribution.  The full text of the license may be found at
   9 http://opensource.org/licenses/bsd-license.php
  10
  11 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  12 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  13
  14 **/
  15
  16 #include <DxeMain.h>
  17
  18 STATIC
  19 VOID
  20 CoreSetInterruptState (
  21   IN BOOLEAN      Enable
  22   )
  23 /*++
  24
  25 Routine Description:
  26
  27   Set Interrupt State
  28
  29 Arguments:
  30
  31   Enable - The state of enable or disable interrupt
  32
  33 Returns:
  34
  35   None
  36
  37 --*/
  38
  39 {
  40   if (gCpu != NULL) {
  41     if (Enable) {
  42       gCpu->EnableInterrupt(gCpu);
  43     } else {
  44       gCpu->DisableInterrupt(gCpu);
  45     }
  46   }
  47 }
  48
  49 //
  50 // Return the highest set bit
  51 //
  52 UINTN
  53 CoreHighestSetBit (
  54   IN UINTN     Number
  55   )
  56 /*++
  57
  58 Routine Description:
  59
  60   Return the highest set bit
  61
  62 Arguments:
  63
  64   Number - The value to check
  65
  66 Returns:
  67
  68   Bit position of the highest set bit
  69
  70 --*/
  71 {
  72   UINTN   msb;
  73
  74   msb = 31;
  75   while ((msb > 0) && ((Number & (UINTN)(1 << msb)) == 0)) {
  76     msb--;
  77   }
  78
  79   return msb;
  80 }
  81
  82
  83
  84 EFI_TPL
  85 EFIAPI
  86 CoreRaiseTpl (
  87   IN EFI_TPL      NewTpl
  88   )
  89 /*++
  90
  91 Routine Description:
  92
  93   Raise the task priority level to the new level.
  94   High level is implemented by disabling processor interrupts.
  95
  96 Arguments:
  97
  98   NewTpl  - New task priority level
  99
 100 Returns:
 101
 102   The previous task priority level
 103
 104 --*/
 105 {
 106   EFI_TPL     OldTpl;
 107
 108   OldTpl = gEfiCurrentTpl;
 109   ASSERT (OldTpl <= NewTpl);
 110   ASSERT (VALID_TPL (NewTpl));
 111
 112   //
 113   // If raising to high level, disable interrupts
 114   //
 115   if (NewTpl >= TPL_HIGH_LEVEL  &&  OldTpl < TPL_HIGH_LEVEL) {
 116     CoreSetInterruptState (FALSE);
 117   }
 118
 119   //
 120   // Set the new value
 121   //
 122   gEfiCurrentTpl = NewTpl;
 123
 124   return OldTpl;
 125 }
 126
 127
 128
 129 VOID
 130 EFIAPI
 131 CoreRestoreTpl (
 132   IN EFI_TPL NewTpl
 133   )
 134 /*++
 135
 136 Routine Description:
 137
 138   Lowers the task priority to the previous value.   If the new
 139   priority unmasks events at a higher priority, they are dispatched.
 140
 141 Arguments:
 142
 143   NewTpl  - New, lower, task priority
 144
 145 Returns:
 146
 147   None
 148
 149 --*/
 150 {
 151   EFI_TPL     OldTpl;
 152
 153   OldTpl = gEfiCurrentTpl;
 154   ASSERT (NewTpl <= OldTpl);
 155   ASSERT (VALID_TPL (NewTpl));
 156
 157   //
 158   // If lowering below HIGH_LEVEL, make sure
 159   // interrupts are enabled
 160   //
 161
 162   if (OldTpl >= TPL_HIGH_LEVEL  &&  NewTpl < TPL_HIGH_LEVEL) {
 163     gEfiCurrentTpl = TPL_HIGH_LEVEL;
 164   }
 165
 166   //
 167   // Dispatch any pending events
 168   //
 169
 170   while ((-2 << NewTpl) & gEventPending) {
 171     gEfiCurrentTpl = CoreHighestSetBit (gEventPending);
 172     if (gEfiCurrentTpl < TPL_HIGH_LEVEL) {
 173       CoreSetInterruptState (TRUE);
 174     }
 175     CoreDispatchEventNotifies (gEfiCurrentTpl);
 176   }
 177
 178   //
 179   // Set the new value
 180   //
 181
 182   gEfiCurrentTpl = NewTpl;
 183
 184   //
 185   // If lowering below HIGH_LEVEL, make sure
 186   // interrupts are enabled
 187   //
 188   if (gEfiCurrentTpl < TPL_HIGH_LEVEL) {
 189     CoreSetInterruptState (TRUE);
 190   }
 191
 192 }