MdeModulePkg/Core/Dxe/Event/Tpl.c

   1 /** @file
   2   Task priority (TPL) functions.
   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 /**
  19   Set Interrupt State.
  20
  21   @param  Enable  The state of enable or disable interrupt
  22
  23 **/
  24 VOID
  25 CoreSetInterruptState (
  26   IN BOOLEAN      Enable
  27   )
  28 {
  29   if (gCpu != NULL) {
  30     if (Enable) {
  31       gCpu->EnableInterrupt(gCpu);
  32     } else {
  33       gCpu->DisableInterrupt(gCpu);
  34     }
  35   }
  36 }
  37
  38 //
  39 // Return the highest set bit
  40 //
  41
  42 /**
  43   Return the highest set bit.
  44
  45   @param  Number  The value to check
  46
  47   @return Bit position of the highest set bit
  48
  49 **/
  50 UINTN
  51 CoreHighestSetBit (
  52   IN UINTN     Number
  53   )
  54 {
  55   UINTN   Msb;
  56
  57   Msb = 31;
  58   while ((Msb > 0) && ((Number & (UINTN)(1 << Msb)) == 0)) {
  59     Msb--;
  60   }
  61
  62   return Msb;
  63 }
  64
  65
  66
  67
  68 /**
  69   Raise the task priority level to the new level.
  70   High level is implemented by disabling processor interrupts.
  71
  72   @param  NewTpl  New task priority level
  73
  74   @return The previous task priority level
  75
  76 **/
  77 EFI_TPL
  78 EFIAPI
  79 CoreRaiseTpl (
  80   IN EFI_TPL      NewTpl
  81   )
  82 {
  83   EFI_TPL     OldTpl;
  84
  85   OldTpl = gEfiCurrentTpl;
  86   ASSERT (OldTpl <= NewTpl);
  87   ASSERT (VALID_TPL (NewTpl));
  88
  89   //
  90   // If raising to high level, disable interrupts
  91   //
  92   if (NewTpl >= TPL_HIGH_LEVEL  &&  OldTpl < TPL_HIGH_LEVEL) {
  93     CoreSetInterruptState (FALSE);
  94   }
  95
  96   //
  97   // Set the new value
  98   //
  99   gEfiCurrentTpl = NewTpl;
 100
 101   return OldTpl;
 102 }
 103
 104
 105
 106
 107 /**
 108   Lowers the task priority to the previous value.   If the new
 109   priority unmasks events at a higher priority, they are dispatched.
 110
 111   @param  NewTpl  New, lower, task priority
 112
 113 **/
 114 VOID
 115 EFIAPI
 116 CoreRestoreTpl (
 117   IN EFI_TPL NewTpl
 118   )
 119 {
 120   EFI_TPL     OldTpl;
 121
 122   OldTpl = gEfiCurrentTpl;
 123   ASSERT (NewTpl <= OldTpl);
 124   ASSERT (VALID_TPL (NewTpl));
 125
 126   //
 127   // If lowering below HIGH_LEVEL, make sure
 128   // interrupts are enabled
 129   //
 130
 131   if (OldTpl >= TPL_HIGH_LEVEL  &&  NewTpl < TPL_HIGH_LEVEL) {
 132     gEfiCurrentTpl = TPL_HIGH_LEVEL;
 133   }
 134
 135   //
 136   // Dispatch any pending events
 137   //
 138
 139   while ((-2 << NewTpl) & gEventPending) {
 140     gEfiCurrentTpl = CoreHighestSetBit (gEventPending);
 141     if (gEfiCurrentTpl < TPL_HIGH_LEVEL) {
 142       CoreSetInterruptState (TRUE);
 143     }
 144     CoreDispatchEventNotifies (gEfiCurrentTpl);
 145   }
 146
 147   //
 148   // Set the new value
 149   //
 150
 151   gEfiCurrentTpl = NewTpl;
 152
 153   //
 154   // If lowering below HIGH_LEVEL, make sure
 155   // interrupts are enabled
 156   //
 157   if (gEfiCurrentTpl < TPL_HIGH_LEVEL) {
 158     CoreSetInterruptState (TRUE);
 159   }
 160
 161 }