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1 //========================================================================== |
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2 // |
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3 // sched/mlqueue.cxx |
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4 // |
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5 // Multi-level queue scheduler class implementation |
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6 // |
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7 //========================================================================== |
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8 //####COPYRIGHTBEGIN#### |
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9 // |
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10 // ------------------------------------------- |
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11 // The contents of this file are subject to the Cygnus eCos Public License |
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12 // Version 1.0 (the "License"); you may not use this file except in |
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13 // compliance with the License. You may obtain a copy of the License at |
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14 // http://sourceware.cygnus.com/ecos |
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15 // |
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16 // Software distributed under the License is distributed on an "AS IS" |
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17 // basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the |
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18 // License for the specific language governing rights and limitations under |
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19 // the License. |
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20 // |
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21 // The Original Code is eCos - Embedded Cygnus Operating System, released |
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22 // September 30, 1998. |
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23 // |
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24 // The Initial Developer of the Original Code is Cygnus. Portions created |
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25 // by Cygnus are Copyright (C) 1998 Cygnus Solutions. All Rights Reserved. |
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26 // ------------------------------------------- |
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27 // |
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28 //####COPYRIGHTEND#### |
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29 //========================================================================== |
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30 //#####DESCRIPTIONBEGIN#### |
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31 // |
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32 // Author(s): nickg |
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33 // Contributors: nickg |
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34 // Date: 1997-09-16 |
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35 // Purpose: Multilevel queue scheduler class implementation |
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36 // Description: This file contains the implementations of |
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37 // Cyg_Scheduler_Implementation and Cyg_SchedThread_Implementation. |
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38 // |
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39 // |
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40 //####DESCRIPTIONEND#### |
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41 // |
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42 //========================================================================== |
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43 |
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44 #include <pkgconf/kernel.h> |
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45 |
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46 #include <cyg/kernel/ktypes.h> // base kernel types |
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47 #include <cyg/infra/cyg_trac.h> // tracing macros |
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48 #include <cyg/infra/cyg_ass.h> // assertion macros |
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49 |
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50 #include <cyg/kernel/sched.hxx> // our header |
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51 |
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52 #include <cyg/hal/hal_arch.h> // Architecture specific definitions |
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53 |
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54 #include <cyg/kernel/thread.inl> // thread inlines |
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55 #include <cyg/kernel/sched.inl> // scheduler inlines |
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56 |
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57 #ifdef CYGSEM_KERNEL_SCHED_MLQUEUE |
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58 |
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59 //------------------------------------------------------------------------- |
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60 // Some local tracing control - a default. |
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61 #ifdef CYGDBG_USE_TRACING |
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62 # if !defined( CYGDBG_INFRA_DEBUG_TRACE_ASSERT_SIMPLE ) && \ |
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63 !defined( CYGDBG_INFRA_DEBUG_TRACE_ASSERT_FANCY ) |
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64 // ie. not a tracing implementation that takes a long time to output |
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65 |
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66 # ifndef CYGDBG_KERNEL_TRACE_TIMESLICE |
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67 # define CYGDBG_KERNEL_TRACE_TIMESLICE |
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68 # endif // control not already defined |
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69 |
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70 # endif // trace implementation not ..._SIMPLE && not ..._FANCY |
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71 #endif // CYGDBG_USE_TRACING |
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72 |
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73 //========================================================================== |
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74 // Cyg_Scheduler_Implementation class static members |
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75 |
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76 #ifdef CYGSEM_KERNEL_SCHED_TIMESLICE |
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77 |
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78 cyg_ucount32 Cyg_Scheduler_Implementation::timeslice_count = |
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79 CYGNUM_KERNEL_SCHED_TIMESLICE_TICKS; |
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80 |
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81 #endif |
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82 |
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83 |
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84 //========================================================================== |
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85 // Cyg_Scheduler_Implementation class members |
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86 |
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87 // ------------------------------------------------------------------------- |
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88 // Constructor. |
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89 |
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90 Cyg_Scheduler_Implementation::Cyg_Scheduler_Implementation() |
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91 { |
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92 CYG_REPORT_FUNCTION(); |
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93 |
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94 queue_map = 0; |
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95 } |
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96 |
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97 // ------------------------------------------------------------------------- |
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98 // Choose the best thread to run next |
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99 |
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100 Cyg_Thread *Cyg_Scheduler_Implementation::schedule() |
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101 { |
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102 CYG_REPORT_FUNCTION(); |
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103 |
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104 // The run queue may _never_ be empty, there is always |
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105 // an idle thread at the lowest priority. |
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106 |
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107 CYG_ASSERT( queue_map != 0, "Run queue empty"); |
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108 CYG_ASSERT( queue_map & (1<<CYG_THREAD_MIN_PRIORITY), "Idle thread vanished!!!"); |
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109 CYG_ASSERT( !run_queue[CYG_THREAD_MIN_PRIORITY].empty(), "Idle thread vanished!!!"); |
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110 |
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111 register cyg_uint32 index; |
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112 |
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113 HAL_LSBIT_INDEX(index, queue_map); |
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114 |
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115 Cyg_Thread *thread = run_queue[index].highpri(); |
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116 |
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117 CYG_ASSERT( thread != NULL , "No threads in run queue"); |
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118 |
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119 return thread; |
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120 } |
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121 |
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122 // ------------------------------------------------------------------------- |
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123 |
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124 void Cyg_Scheduler_Implementation::add_thread(Cyg_Thread *thread) |
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125 { |
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126 CYG_REPORT_FUNCTION(); |
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127 |
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128 cyg_priority pri = thread->priority; |
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129 Cyg_ThreadQueue_Implementation *queue = &run_queue[pri]; |
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130 |
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131 // If the thread is on some other queue, remove it |
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132 // here. |
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133 if( thread->queue != NULL ) |
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134 { |
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135 thread->queue->remove(thread); |
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136 thread->queue = NULL; |
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137 } |
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138 |
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139 if( queue->empty() ) |
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140 { |
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141 // set the map bit and ask for a reschedule if this is a |
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142 // new highest priority thread. |
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143 |
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144 queue_map |= (1<<pri); |
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145 |
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146 // If the new thread is higher priority than the |
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147 // current thread, request a reschedule. |
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148 |
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149 if( pri < Cyg_Scheduler::get_current_thread()->priority ) |
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150 need_reschedule = true; |
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151 |
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152 } |
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153 // else the queue already has an occupant, queue behind him |
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154 |
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155 CYG_ASSERT( queue_map != 0, "Run queue empty"); |
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156 CYG_ASSERT( queue_map & (1<<pri), "Queue map bit not set for pri"); |
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157 CYG_ASSERT( queue_map & (1<<CYG_THREAD_MIN_PRIORITY), "Idle thread vanished!!!"); |
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158 // CYG_ASSERT( !run_queue[CYG_THREAD_MIN_PRIORITY].empty(), "Idle thread vanished!!!"); |
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159 |
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160 queue->enqueue(thread); |
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161 } |
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162 |
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163 // ------------------------------------------------------------------------- |
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164 |
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165 void Cyg_Scheduler_Implementation::rem_thread(Cyg_Thread *thread) |
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166 { |
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167 CYG_REPORT_FUNCTION(); |
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168 |
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169 CYG_ASSERT( queue_map != 0, "Run queue empty"); |
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170 |
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171 cyg_priority pri = thread->priority; |
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172 Cyg_ThreadQueue_Implementation *queue = &run_queue[pri]; |
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173 |
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174 CYG_ASSERT( pri != CYG_THREAD_MIN_PRIORITY, "Idle thread trying to sleep!"); |
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175 CYG_ASSERT( queue_map & (1<<pri), "Queue map bit not set for pri"); |
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176 CYG_ASSERT( !run_queue[CYG_THREAD_MIN_PRIORITY].empty(), "Idle thread vanished!!!"); |
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177 |
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178 // remove thread from queue |
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179 queue->remove(thread); |
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180 |
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181 if( queue->empty() ) |
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182 { |
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183 // If this was only thread in |
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184 // queue, clear map. |
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185 |
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186 queue_map &= ~(1<<pri); |
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187 } |
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188 |
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189 CYG_ASSERT( queue_map != 0, "Run queue empty"); |
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190 CYG_ASSERT( queue_map & (1<<CYG_THREAD_MIN_PRIORITY), "Idle thread vanished!!!"); |
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191 CYG_ASSERT( !run_queue[CYG_THREAD_MIN_PRIORITY].empty(), "Idle thread vanished!!!"); |
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192 } |
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193 |
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194 // ------------------------------------------------------------------------- |
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195 // register thread with scheduler |
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196 |
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197 void Cyg_Scheduler_Implementation::register_thread(Cyg_Thread *thread) |
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198 { |
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199 CYG_REPORT_FUNCTION(); |
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200 |
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201 // No registration necessary in this scheduler |
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202 } |
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203 |
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204 // ------------------------------------------------------------------------- |
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205 |
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206 // deregister thread |
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207 void Cyg_Scheduler_Implementation::deregister_thread(Cyg_Thread *thread) |
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208 { |
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209 CYG_REPORT_FUNCTION(); |
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210 |
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211 // No registration necessary in this scheduler |
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212 } |
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213 |
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214 // ------------------------------------------------------------------------- |
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215 // Test the given priority for uniqueness |
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216 |
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217 cyg_bool Cyg_Scheduler_Implementation::unique( cyg_priority priority) |
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218 { |
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219 CYG_REPORT_FUNCTION(); |
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220 |
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221 // Priorities are not unique |
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222 return true; |
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223 } |
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224 |
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225 //========================================================================== |
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226 // Support for timeslicing option |
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227 |
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228 #ifdef CYGSEM_KERNEL_SCHED_TIMESLICE |
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229 |
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230 void Cyg_Scheduler_Implementation::timeslice() |
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231 { |
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232 #ifdef CYGDBG_KERNEL_TRACE_TIMESLICE |
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233 CYG_REPORT_FUNCTION(); |
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234 #endif |
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235 CYG_ASSERT( queue_map != 0, "Run queue empty"); |
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236 CYG_ASSERT( queue_map & (1<<CYG_THREAD_MIN_PRIORITY), "Idle thread vanished!!!"); |
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237 |
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238 if( --timeslice_count == 0 ) |
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239 { |
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240 CYG_INSTRUMENT_SCHED(TIMESLICE,0,0); |
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241 #ifdef CYGDBG_KERNEL_TRACE_TIMESLICE |
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242 CYG_TRACE0( true, "quantum consumed, time to reschedule" ); |
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243 #endif |
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244 // And force the current thread to yield. |
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245 current_thread->yield(); |
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246 } |
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247 |
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248 CYG_ASSERT( queue_map & (1<<CYG_THREAD_MIN_PRIORITY), "Idle thread vanished!!!"); |
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249 CYG_ASSERT( !run_queue[CYG_THREAD_MIN_PRIORITY].empty(), "Idle thread vanished!!!"); |
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250 #ifdef CYGDBG_KERNEL_TRACE_TIMESLICE |
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251 CYG_REPORT_RETURN(); |
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252 #endif |
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253 } |
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254 |
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255 #endif |
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256 |
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257 //========================================================================== |
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258 // Cyg_Cyg_SchedThread_Implementation class members |
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259 |
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260 Cyg_SchedThread_Implementation::Cyg_SchedThread_Implementation |
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261 ( |
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262 CYG_ADDRWORD sched_info |
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263 ) |
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264 { |
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265 CYG_REPORT_FUNCTION(); |
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266 |
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267 // Create all threads at maximum priority |
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268 priority = (cyg_priority)sched_info; |
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269 |
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270 // point the next and prev field at this thread. |
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271 |
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272 next = prev = CYG_CLASSFROMBASE(Cyg_Thread, |
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273 Cyg_SchedThread_Implementation, |
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274 this); |
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275 } |
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276 |
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277 // ------------------------------------------------------------------------- |
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278 // Insert thread in front of this |
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279 |
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280 void Cyg_SchedThread_Implementation::insert( Cyg_Thread *thread) |
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281 { |
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282 CYG_REPORT_FUNCTION(); |
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283 |
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284 thread->next = CYG_CLASSFROMBASE(Cyg_Thread, |
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285 Cyg_SchedThread_Implementation, |
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286 this); |
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287 thread->prev = prev; |
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288 prev->next = thread; |
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289 prev = thread; |
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290 } |
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291 |
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292 // ------------------------------------------------------------------------- |
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293 // remove this from queue |
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294 |
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295 void Cyg_SchedThread_Implementation::remove() |
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296 { |
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297 CYG_REPORT_FUNCTION(); |
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298 |
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299 next->prev = prev; |
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300 prev->next = next; |
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301 next = prev = CYG_CLASSFROMBASE(Cyg_Thread, |
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302 Cyg_SchedThread_Implementation, |
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303 this); |
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304 } |
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305 |
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306 // ------------------------------------------------------------------------- |
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307 // Yield the processor to another thread |
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308 |
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309 void Cyg_SchedThread_Implementation::yield() |
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310 { |
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311 CYG_REPORT_FUNCTION(); |
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312 |
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313 // Prevent preemption |
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314 Cyg_Scheduler::lock(); |
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315 |
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316 Cyg_Thread *thread = CYG_CLASSFROMBASE(Cyg_Thread, |
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317 Cyg_SchedThread_Implementation, |
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318 this); |
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319 |
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320 // Only do this if this thread is running. If it is not, there |
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321 // is no point. |
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322 |
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323 if( thread->get_state() == Cyg_Thread::RUNNING ) |
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324 { |
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325 // To yield we simply rotate the appropriate |
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326 // run queue to the next thread and reschedule. |
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327 |
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328 CYG_ASSERTCLASS( thread, "Bad current thread"); |
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329 |
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330 Cyg_Scheduler *sched = &Cyg_Scheduler::scheduler; |
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331 |
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332 CYG_ASSERTCLASS( sched, "Bad scheduler"); |
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333 |
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334 cyg_priority pri = thread->priority; |
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335 Cyg_ThreadQueue_Implementation *queue = &sched->run_queue[pri]; |
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336 |
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337 queue->rotate(); |
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338 |
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339 if( queue->highpri() != thread ) |
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340 sched->need_reschedule = true; |
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341 #ifdef CYGSEM_KERNEL_SCHED_TIMESLICE |
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342 // Reset the timeslice counter so that this thread gets a full |
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343 // quantum. |
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344 else Cyg_Scheduler::reset_timeslice_count(); |
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345 #endif |
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346 } |
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347 |
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348 // Unlock the scheduler and switch threads |
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349 Cyg_Scheduler::unlock(); |
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350 |
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351 } |
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352 |
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353 // ------------------------------------------------------------------------- |
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354 // Rotate the run queue at a specified priority. |
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355 // (pri is the decider, no this, so the routine is static) |
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356 |
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357 void |
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358 Cyg_SchedThread_Implementation::rotate_queue( cyg_priority pri ) |
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359 { |
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360 CYG_REPORT_FUNCTION(); |
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361 |
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362 // Prevent preemption |
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363 Cyg_Scheduler::lock(); |
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364 |
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365 Cyg_Scheduler *sched = &Cyg_Scheduler::scheduler; |
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366 |
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367 CYG_ASSERTCLASS( sched, "Bad scheduler"); |
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368 |
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369 Cyg_ThreadQueue_Implementation *queue = &sched->run_queue[pri]; |
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370 |
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371 if ( !queue->empty() ) { |
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372 queue->rotate(); |
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373 sched->need_reschedule = true; |
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374 } |
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375 |
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376 // Unlock the scheduler and switch threads |
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377 Cyg_Scheduler::unlock(); |
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378 |
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379 } |
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380 |
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381 //========================================================================== |
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382 // Cyg_ThreadQueue_Implementation class members |
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383 |
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384 Cyg_ThreadQueue_Implementation::Cyg_ThreadQueue_Implementation() |
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385 { |
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386 CYG_REPORT_FUNCTION(); |
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387 |
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388 queue = NULL; // empty queue |
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389 } |
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390 |
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391 |
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392 |
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393 void Cyg_ThreadQueue_Implementation::enqueue(Cyg_Thread *thread) |
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394 { |
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395 CYG_REPORT_FUNCTION(); |
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396 |
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397 if( queue == NULL ) queue = thread; |
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398 else queue->insert(thread); |
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399 |
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400 thread->queue = CYG_CLASSFROMBASE(Cyg_ThreadQueue, |
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401 Cyg_ThreadQueue_Implementation, |
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402 this); |
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403 |
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404 } |
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405 |
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406 // ------------------------------------------------------------------------- |
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407 |
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408 Cyg_Thread *Cyg_ThreadQueue_Implementation::dequeue() |
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409 { |
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410 CYG_REPORT_FUNCTION(); |
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411 |
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412 if( queue == NULL ) return NULL; |
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413 |
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414 Cyg_Thread *thread = queue; |
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415 |
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416 if( thread->next == thread ) |
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417 { |
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418 // sole thread on list, NULL out ptr |
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419 queue = NULL; |
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420 } |
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421 else |
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422 { |
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423 // advance to next and remove thread |
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424 queue = thread->next; |
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425 thread->remove(); |
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426 } |
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427 |
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428 thread->queue = NULL; |
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429 |
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430 return thread; |
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431 } |
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432 |
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433 // ------------------------------------------------------------------------- |
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434 |
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435 Cyg_Thread *Cyg_ThreadQueue_Implementation::highpri() |
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436 { |
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437 CYG_REPORT_FUNCTION(); |
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438 |
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439 return queue; |
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440 } |
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441 |
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442 // ------------------------------------------------------------------------- |
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443 |
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444 void Cyg_ThreadQueue_Implementation::remove(Cyg_Thread *thread) |
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445 { |
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446 CYG_REPORT_FUNCTION(); |
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447 |
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448 // If the thread we want it the at the head |
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449 // of the list, and is on its own, clear the |
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450 // list and return. Otherwise advance to the |
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451 // next thread and remove ours. If the thread |
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452 // is not at the head of the list, just dequeue |
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453 // it. |
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454 |
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455 thread->queue = NULL; |
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456 |
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457 if( queue == thread ) |
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458 { |
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459 if( thread->next == thread ) |
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460 { |
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461 queue = NULL; |
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462 return; |
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463 } |
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464 else queue = thread->next; |
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465 } |
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466 |
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467 thread->Cyg_SchedThread_Implementation::remove(); |
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468 |
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469 } |
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470 |
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471 // ------------------------------------------------------------------------- |
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472 // Rotate the front thread on the queue to the back. |
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473 |
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474 void Cyg_ThreadQueue_Implementation::rotate() |
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475 { |
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476 CYG_REPORT_FUNCTION(); |
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477 |
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478 queue = queue->next; |
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479 } |
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480 |
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481 // ------------------------------------------------------------------------- |
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482 |
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483 #endif |
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484 |
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485 // ------------------------------------------------------------------------- |
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486 // EOF sched/mlqueue.cxx |
