2 FreeRTOS V6.1.0 - Copyright (C) 2010 Real Time Engineers Ltd.
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4 ***************************************************************************
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8 * + New to FreeRTOS, *
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9 * + Wanting to learn FreeRTOS or multitasking in general quickly *
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10 * + Looking for basic training, *
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11 * + Wanting to improve your FreeRTOS skills and productivity *
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13 * then take a look at the FreeRTOS books - available as PDF or paperback *
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15 * "Using the FreeRTOS Real Time Kernel - a Practical Guide" *
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16 * http://www.FreeRTOS.org/Documentation *
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18 * A pdf reference manual is also available. Both are usually delivered *
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19 * to your inbox within 20 minutes to two hours when purchased between 8am *
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20 * and 8pm GMT (although please allow up to 24 hours in case of *
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21 * exceptional circumstances). Thank you for your support! *
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23 ***************************************************************************
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25 This file is part of the FreeRTOS distribution.
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27 FreeRTOS is free software; you can redistribute it and/or modify it under
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28 the terms of the GNU General Public License (version 2) as published by the
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29 Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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30 ***NOTE*** The exception to the GPL is included to allow you to distribute
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31 a combined work that includes FreeRTOS without being obliged to provide the
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32 source code for proprietary components outside of the FreeRTOS kernel.
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33 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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34 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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35 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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36 more details. You should have received a copy of the GNU General Public
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37 License and the FreeRTOS license exception along with FreeRTOS; if not it
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38 can be viewed here: http://www.freertos.org/a00114.html and also obtained
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39 by writing to Richard Barry, contact details for whom are available on the
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44 http://www.FreeRTOS.org - Documentation, latest information, license and
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47 http://www.SafeRTOS.com - A version that is certified for use in safety
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50 http://www.OpenRTOS.com - Commercial support, development, porting,
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51 licensing and training services.
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54 /* Scheduler includes. */
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55 #include "FreeRTOS.h"
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59 //FILE *pfTraceFile = NULL;
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60 //#define vPortTrace( x ) if( pfTraceFile == NULL ) pfTraceFile = fopen( "c:/temp/trace.txt", "w" ); if( pfTraceFile != NULL ) fprintf( pfTraceFile, x )
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61 #define vPortTrace( x ) ( void ) x
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63 #define portMAX_INTERRUPTS ( ( unsigned long ) sizeof( unsigned long ) * 8UL ) /* The number of bits in an unsigned long. */
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64 #define portNO_CRITICAL_NESTING ( ( unsigned long ) 0 )
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67 * Created as a high priority thread, this function uses a timer to simulate
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68 * a tick interrupt being generated on an embedded target. In this Windows
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69 * environment the timer does not achieve anything approaching real time
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70 * performance though.
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72 static DWORD WINAPI prvSimulatedPeripheralTimer( LPVOID lpParameter );
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75 * Process all the simulated interrupts - each represented by a bit in
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76 * ulPendingInterrupts variable.
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78 static void prvProcessPseudoInterrupts( void );
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80 /*-----------------------------------------------------------*/
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82 /* The WIN32 simulator runs each task in a thread. The context switching is
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83 managed by the threads, so the task stack does not have to be managed directly,
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84 although the task stack is still used to hold an xThreadState structure this is
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85 the only thing it will ever hold. The structure indirectly maps the task handle
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86 to a thread handle. */
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89 /* Set to true if the task run by the thread yielded control to the pseudo
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90 interrupt handler manually - either by yielding or when exiting a critical
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91 section while pseudo interrupts were pending. */
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92 long lWaitingInterruptAck;
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94 /* Critical nesting count of the task - each task has its own. */
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95 portSTACK_TYPE ulCriticalNesting;
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97 /* Handle of the thread that executes the task. */
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101 /* Pseudo interrupts waiting to be processed. This is a bit mask where each
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102 bit represents one interrupt, so a maximum of 32 interrupts can be simulated. */
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103 static volatile unsigned long ulPendingInterrupts = 0UL;
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105 /* An event used to inform the pseudo interrupt processing thread (a high
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106 priority thread that simulated interrupt processing) that an interrupt is
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108 static void *pvInterruptEvent = NULL;
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110 /* Mutex used to protect all the pseudo interrupt variables that are accessed
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111 by multiple threads. */
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112 static void *pvInterruptEventMutex = NULL;
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114 /* Events used to manage sequencing. */
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115 static void *pvTickAcknowledgeEvent = NULL, *pvInterruptAcknowledgeEvent = NULL;
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117 /* The critical nesting count for the currently executing task. This is
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118 initialised to a non-zero value so interrupts do not become enabled during
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119 the initialisation phase. As each task has its own critical nesting value
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120 ulCriticalNesting will get set to zero when the first task runs. This
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121 initialisation is probably not critical in this simulated environment as the
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122 pseudo interrupt handlers do not get created until the FreeRTOS scheduler is
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124 static unsigned long ulCriticalNesting = 9999UL;
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126 /* Handlers for all the simulated software interrupts. The first two positions
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127 are used for the Yield and Tick interrupts so are handled slightly differently,
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128 all the other interrupts can be user defined. */
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129 static void (*vIsrHandler[ portMAX_INTERRUPTS ])( void ) = { 0 };
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131 /* Pointer to the TCB of the currently executing task. */
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132 extern void *pxCurrentTCB;
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134 /*-----------------------------------------------------------*/
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136 static DWORD WINAPI prvSimulatedPeripheralTimer( LPVOID lpParameter )
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138 /* Just to prevent compiler warnings. */
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139 ( void ) lpParameter;
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143 vPortTrace( "prvSimulatedPeripheralTimer: Tick acked, re-Sleeping()\r\n" );
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145 /* Wait until the timer expires and we can access the pseudo interrupt
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146 variables. *NOTE* this is not a 'real time' way of generating tick
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147 events as the next wake time should be relative to the previous wake
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148 time, not the time that Sleep() is called. It is done this way to
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149 prevent overruns in this very non real time simulated/emulated
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151 Sleep( portTICK_RATE_MS );
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153 vPortTrace( "prvSimulatedPeripheralTimer: Sleep expired, waiting interrupt event mutex\r\n" );
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154 WaitForSingleObject( pvInterruptEventMutex, INFINITE );
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155 vPortTrace( "prvSimulatedPeripheralTimer: Got interrupt event mutex\r\n" );
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157 /* The timer has expired, generate the simulated tick event. */
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158 ulPendingInterrupts |= ( 1 << portINTERRUPT_TICK );
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160 /* The interrupt is now pending - but should only be processed if
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161 interrupts are actually enabled. */
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162 if( ulCriticalNesting == 0UL )
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164 vPortTrace( "prvSimulatedPeripheralTimer: Setting interrupt event to signal tick\r\n" );
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165 SetEvent( pvInterruptEvent );
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167 /* Give back the mutex so the pseudo interrupt handler unblocks
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168 and can access the interrupt handler variables. This high priority
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169 task will then loop back round after waiting for the lower priority
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170 pseudo interrupt handler thread to acknowledge the tick. */
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171 vPortTrace( "prvSimulatedPeripheralTimer: Releasing interrupt event mutex so tick can be processed\r\n" );
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172 SignalObjectAndWait( pvInterruptEventMutex, pvTickAcknowledgeEvent, INFINITE, FALSE );
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176 ReleaseMutex( pvInterruptEventMutex );
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180 /*-----------------------------------------------------------*/
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182 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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184 xThreadState *pxThreadState = NULL;
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186 /* In this simulated case a stack is not initialised, but instead a thread
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187 is created that will execute the task being created. The thread handles
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188 the context switching itself. The xThreadState object is placed onto
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189 the stack that was created for the task - so the stack buffer is still
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190 used, just not in the conventional way. It will not be used for anything
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191 other than holding this structure. */
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192 pxThreadState = ( xThreadState * ) ( pxTopOfStack - sizeof( xThreadState ) );
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194 /* Create the thread itself. */
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195 pxThreadState->pvThread = ( void * ) CreateThread( NULL, 0, ( LPTHREAD_START_ROUTINE ) pxCode, pvParameters, CREATE_SUSPENDED, NULL );
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196 SetThreadPriorityBoost( pxThreadState->pvThread, TRUE );
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197 pxThreadState->ulCriticalNesting = portNO_CRITICAL_NESTING;
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198 pxThreadState->lWaitingInterruptAck = pdFALSE;
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199 SetThreadPriority( pxThreadState->pvThread, THREAD_PRIORITY_IDLE );
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201 return ( portSTACK_TYPE * ) pxThreadState;
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203 /*-----------------------------------------------------------*/
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205 portBASE_TYPE xPortStartScheduler( void )
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208 long lSuccess = pdPASS;
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209 xThreadState *pxThreadState;
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211 /* Create the events and mutexes that are used to synchronise all the
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213 pvInterruptEventMutex = CreateMutex( NULL, FALSE, NULL );
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214 pvInterruptEvent = CreateEvent( NULL, FALSE, FALSE, NULL );
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215 pvTickAcknowledgeEvent = CreateEvent( NULL, FALSE, FALSE, NULL );
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216 pvInterruptAcknowledgeEvent = CreateEvent( NULL, FALSE, FALSE, NULL );
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218 if( ( pvInterruptEventMutex == NULL ) || ( pvInterruptEvent == NULL ) || ( pvTickAcknowledgeEvent == NULL ) || ( pvInterruptAcknowledgeEvent == NULL ) )
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223 /* Set the priority of this thread such that it is above the priority of
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224 the threads that run tasks. This higher priority is required to ensure
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225 pseudo interrupts take priority over tasks. */
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226 SetPriorityClass( GetCurrentProcess(), ABOVE_NORMAL_PRIORITY_CLASS );
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227 pvHandle = GetCurrentThread();
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228 if( pvHandle == NULL )
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233 if( lSuccess == pdPASS )
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235 if( SetThreadPriority( pvHandle, THREAD_PRIORITY_HIGHEST ) == 0 )
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239 SetThreadPriorityBoost( pvHandle, TRUE );
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242 if( lSuccess == pdPASS )
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244 /* Start the thread that simulates the timer peripheral to generate
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245 tick interrupts. */
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246 pvHandle = CreateThread( NULL, 0, prvSimulatedPeripheralTimer, NULL, 0, NULL );
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247 if( pvHandle != NULL )
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249 SetThreadPriority( pvHandle, THREAD_PRIORITY_HIGHEST );
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250 SetThreadPriorityBoost( pvHandle, TRUE );
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253 /* Start the highest priority task by obtaining its associated thread
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254 state structure, in which is stored the thread handle. */
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255 pxThreadState = ( xThreadState * ) *( ( unsigned long * ) pxCurrentTCB );
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256 ulCriticalNesting = portNO_CRITICAL_NESTING;
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258 vPortTrace( "Created system threads, starting task" );
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260 /* Bump up the priority of the thread that is going to run, in the
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261 hope that this will asist in getting the Windows thread scheduler to
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262 behave as an embedded engineer might expect. */
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263 SetThreadPriority( pxThreadState->pvThread, THREAD_PRIORITY_ABOVE_NORMAL );
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264 ResumeThread( pxThreadState->pvThread );
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266 /* Handle all pseudo interrupts - including yield requests and
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267 simulated ticks. */
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268 prvProcessPseudoInterrupts();
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271 /* Would not expect to return from prvProcessPseudoInterrupts(), so should
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275 /*-----------------------------------------------------------*/
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277 static void prvProcessPseudoInterrupts( void )
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279 long lSwitchRequired;
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280 xThreadState *pxThreadState;
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281 void *pvObjectList[ 2 ];
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283 //char cTraceBuffer[ 256 ];
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285 vPortTrace( "Entering prvProcessPseudoInterrupts\r\n" );
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287 /* Going to block on the mutex that ensured exclusive access to the pseudo
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288 interrupt objects, and the event that signals that a pseudo interrupt
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289 should be processed. */
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290 pvObjectList[ 0 ] = pvInterruptEventMutex;
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291 pvObjectList[ 1 ] = pvInterruptEvent;
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295 vPortTrace( "prvProcessPseudoInterrupts: Waiting for next interrupt event\r\n" );
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296 WaitForMultipleObjects( sizeof( pvObjectList ) / sizeof( void * ), pvObjectList, TRUE, INFINITE );
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297 vPortTrace( "prvProcessPseudoInterrupts: Got interrupt event and mutex\r\n" );
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299 /* Used to indicate whether the pseudo interrupt processing has
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300 necessitated a context switch to another task/thread. */
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301 lSwitchRequired = pdFALSE;
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303 /* For each interrupt we are interested in processing, each of which is
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304 represented by a bit in the 32bit ulPendingInterrupts variable. */
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305 for( i = 0; i < portMAX_INTERRUPTS; i++ )
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307 /* Is the pseudo interrupt pending? */
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308 if( ulPendingInterrupts & ( 1UL << i ) )
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312 case portINTERRUPT_YIELD:
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314 vPortTrace( "prvProcessPseudoInterrupts: Processing Yield\r\n" );
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315 lSwitchRequired = pdTRUE;
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317 /* Clear the interrupt pending bit. */
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318 ulPendingInterrupts &= ~( 1UL << portINTERRUPT_YIELD );
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321 case portINTERRUPT_TICK:
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323 /* Tick interrupts should only be processed if the
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324 critical nesting count is zero. The critical nesting
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325 count represents the interrupt mask on real target
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326 hardware. The thread that genereates ticks will not
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327 actually ask for the tick to be processed unless the
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328 critical nesting count is zero anyway, but it is
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329 possible that a tick is pending when a yield is
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330 performed (depending on if the simulation/emulation is
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331 set up to process yields while within a critical
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333 vPortTrace( "prvProcessPseudoInterrupts: Processing tick event\r\n" );
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334 if( ulCriticalNesting == 0UL )
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336 /* Process the tick itself. */
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337 vPortTrace( "prvProcessPseudoInterrupts: Incrementing tick\r\n" );
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338 vTaskIncrementTick();
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339 #if( configUSE_PREEMPTION != 0 )
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341 /* A context switch is only automatically
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342 performed from the tick interrupt if the
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343 pre-emptive scheduler is being used. */
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344 lSwitchRequired = pdTRUE;
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348 /* Clear the interrupt pending bit. */
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349 ulPendingInterrupts &= ~( 1UL << portINTERRUPT_TICK );
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351 vPortTrace( "prvProcessPseudoInterrupts: Acking tick\r\n" );
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352 SetEvent( pvTickAcknowledgeEvent );
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356 /* The tick is held pending in ulCriticalNesting
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357 until such time that pseudo interrupts are enabled
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364 if( ulCriticalNesting == 0UL )
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366 /* Is a handler installed? */
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367 if( vIsrHandler[ i ] != NULL )
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369 lSwitchRequired = pdTRUE;
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371 /* Run the actual handler. */
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372 vIsrHandler[ i ]();
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374 /* Clear the interrupt pending bit. */
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375 ulPendingInterrupts &= ~( 1UL << i );
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377 /* TODO: Need to have some sort of handshake
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378 event here for non-tick and none yield
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387 if( lSwitchRequired != pdFALSE )
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389 void *pvOldCurrentTCB;
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391 pvOldCurrentTCB = pxCurrentTCB;
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393 /* Save the state of the current thread before suspending it. */
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394 pxThreadState = ( xThreadState *) *( ( unsigned long * ) pxCurrentTCB );
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395 pxThreadState->ulCriticalNesting = ulCriticalNesting ;
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397 /* Select the next task to run. */
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398 vTaskSwitchContext();
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400 /* If the task selected to enter the running state is not the task
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401 that is already in the running state. */
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402 if( pvOldCurrentTCB != pxCurrentTCB )
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404 /* Suspend the old thread. */
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405 SetThreadPriority( pxThreadState->pvThread, THREAD_PRIORITY_IDLE );
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406 SuspendThread( pxThreadState->pvThread );
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408 //sprintf( cTraceBuffer, "Event processor: suspending %s, resuming %s\r\n", ((xTCB*)pvOldCurrentTCB)->pcTaskName, ((xTCB*)pxCurrentTCB)->pcTaskName );
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409 //vPortTrace( cTraceBuffer );
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411 /* Obtain the state of the task now selected to enter the Running state. */
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412 pxThreadState = ( xThreadState * ) ( *( unsigned long *) pxCurrentTCB );
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413 ulCriticalNesting = pxThreadState->ulCriticalNesting;
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414 SetThreadPriority( pxThreadState->pvThread, THREAD_PRIORITY_ABOVE_NORMAL );
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415 ResumeThread( pxThreadState->pvThread );
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417 if( pxThreadState->lWaitingInterruptAck == pdTRUE )
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419 pxThreadState->lWaitingInterruptAck = pdFALSE;
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420 vPortTrace( "prvProcessPseudoInterrupts: Acking interrupt\r\n" );
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421 SetEvent( pvInterruptAcknowledgeEvent );
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427 /* On exiting a critical section a task may have blocked on the
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428 interrupt event when only a tick needed processing, in which case
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429 it will not have been released from waiting on the event yet. */
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430 pxThreadState = ( xThreadState * ) ( *( unsigned long *) pxCurrentTCB );
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431 if( pxThreadState->lWaitingInterruptAck == pdTRUE )
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433 pxThreadState->lWaitingInterruptAck = pdFALSE;
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434 vPortTrace( "prvProcessPseudoInterrupts: Acking interrupt even though a yield has not been performed.\r\n" );
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435 SetEvent( pvInterruptAcknowledgeEvent );
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439 ReleaseMutex( pvInterruptEventMutex );
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442 /*-----------------------------------------------------------*/
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444 void vPortEndScheduler( void )
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447 /*-----------------------------------------------------------*/
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449 void vPortGeneratePseudoInterrupt( unsigned long ulInterruptNumber )
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451 xThreadState *pxThreadState;
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453 if( ( ulInterruptNumber < portMAX_INTERRUPTS ) && ( pvInterruptEventMutex != NULL ) )
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455 /* Yield interrupts are processed even when critical nesting is non-zero. */
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456 WaitForSingleObject( pvInterruptEventMutex, INFINITE );
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457 ulPendingInterrupts |= ( 1 << ulInterruptNumber );
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459 if( ulCriticalNesting == 0 ) //|| ( ulInterruptNumber == portINTERRUPT_YIELD ) )
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461 /* The event handler needs to know to signal the interrupt acknowledge event
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462 the next time this task runs. */
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463 pxThreadState = ( xThreadState * ) *( ( unsigned long * ) pxCurrentTCB );
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464 pxThreadState->lWaitingInterruptAck = pdTRUE;
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466 vPortTrace( "vPortGeneratePseudoInterrupt: Got interrupt mutex, about to signal interrupt event\r\n" );
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467 SetEvent( pvInterruptEvent );
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469 /* The interrupt ack event should not be signaled yet - if it is then there
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470 is an error in the logical simulation. */
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471 if( WaitForSingleObject( pvInterruptAcknowledgeEvent, 0 ) != WAIT_TIMEOUT )
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473 /* This line is for a break point only. */
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477 SignalObjectAndWait( pvInterruptEventMutex, pvInterruptAcknowledgeEvent, INFINITE, FALSE );
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478 vPortTrace( "vPortGeneratePseudoInterrupt: About to release interrupt event mutex\r\n" );
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479 // ReleaseMutex( pvInterruptEventMutex );
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480 vPortTrace( "vPortGeneratePseudoInterrupt: Interrupt event mutex released, going to wait for interrupt ack\r\n" );
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482 // WaitForSingleObject( pvInterruptAcknowledgeEvent, INFINITE );
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483 vPortTrace( "vPortGeneratePseudoInterrupt: Interrupt acknowledged, leaving vPortGeneratePseudoInterrupt()\r\n" );
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487 ReleaseMutex( pvInterruptEventMutex );
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491 /*-----------------------------------------------------------*/
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493 void vPortSetInterruptHandler( unsigned long ulInterruptNumber, void (*pvHandler)( void ) )
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495 if( ulInterruptNumber < portMAX_INTERRUPTS )
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497 if( pvInterruptEventMutex != NULL )
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499 WaitForSingleObject( pvInterruptEventMutex, INFINITE );
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500 vIsrHandler[ ulInterruptNumber ] = pvHandler;
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501 ReleaseMutex( pvInterruptEventMutex );
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505 vIsrHandler[ ulInterruptNumber ] = pvHandler;
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509 /*-----------------------------------------------------------*/
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511 void vPortEnterCritical( void )
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513 if( xTaskGetSchedulerState() != taskSCHEDULER_NOT_STARTED )
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515 WaitForSingleObject( pvInterruptEventMutex, INFINITE );
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516 // SuspendThread( pvSimulatedTimerThread );
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517 ulCriticalNesting++;
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518 ReleaseMutex( pvInterruptEventMutex );
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522 ulCriticalNesting++;
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525 /*-----------------------------------------------------------*/
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527 void vPortExitCritical( void )
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529 xThreadState *pxThreadState;
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531 if( ulCriticalNesting > portNO_CRITICAL_NESTING )
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533 if( ulCriticalNesting == ( portNO_CRITICAL_NESTING + 1 ) )
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535 /* Wait for the interrupt event mutex prior to manipulating or
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536 testing the pseudo interrupt control variables. */
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537 WaitForSingleObject( pvInterruptEventMutex, INFINITE );
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538 vPortTrace( "vPortExitCritical: Got interrupt event mutex\r\n" );
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540 // ResumeThread( pvSimulatedTimerThread );
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542 /* Now it is safe to decrement the critical nesting count as no
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543 tick events will be processed until the interrupt event mutex is
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545 ulCriticalNesting--;
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547 /* Were any interrupts set to pending while interrupts were
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548 (pseudo) disabled? */
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549 if( ulPendingInterrupts != 0UL )
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551 SetEvent( pvInterruptEvent );
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553 /* The interrupt ack event should not be signaled yet - if it
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554 is then there is an error in the logical simulation. */
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555 if( WaitForSingleObject( pvInterruptAcknowledgeEvent, 0 ) != WAIT_TIMEOUT )
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557 /* This line is for a break point only. */
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561 /* The event handler needs to know to signal the interrupt
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562 acknowledge event the next time this task runs. */
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563 pxThreadState = ( xThreadState * ) *( ( unsigned long * ) pxCurrentTCB );
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564 pxThreadState->lWaitingInterruptAck = pdTRUE;
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566 SignalObjectAndWait( pvInterruptEventMutex, pvInterruptAcknowledgeEvent, INFINITE, FALSE );
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567 /* Give back the interrupt event mutex so the event can be processed. */
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568 // ReleaseMutex( pvInterruptEventMutex );
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570 // vPortTrace( "vPortExitCritical: Waiting interrupt ack\r\n" );
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571 // WaitForSingleObject( pvInterruptAcknowledgeEvent, INFINITE );
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572 vPortTrace( "vPortExitCritical: Interrupt acknowledged, leaving critical section code\r\n" );
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576 /* Can't leave here without giving back the interrupt event
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578 ReleaseMutex( pvInterruptEventMutex );
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583 /* Tick interrupts will still not be processed as the critical
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584 nesting depth will not be zero. */
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585 ulCriticalNesting--;
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