2 FreeRTOS V6.1.1 - Copyright (C) 2011 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 #define portMAX_INTERRUPTS ( ( unsigned long ) sizeof( unsigned long ) * 8UL ) /* The number of bits in an unsigned long. */
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60 #define portNO_CRITICAL_NESTING ( ( unsigned long ) 0 )
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63 * Created as a high priority thread, this function uses a timer to simulate
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64 * a tick interrupt being generated on an embedded target. In this Windows
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65 * environment the timer does not achieve anything approaching real time
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66 * performance though.
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68 static DWORD WINAPI prvSimulatedPeripheralTimer( LPVOID lpParameter );
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71 * Process all the simulated interrupts - each represented by a bit in
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72 * ulPendingInterrupts variable.
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74 static void prvProcessSimulatedInterrupts( void );
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77 * Interrupt handlers used by the kernel itself. These are executed from the
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78 * simulated interrupt handler thread.
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80 static unsigned long prvProcessDeleteThreadInterrupt( void );
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81 static unsigned long prvProcessYieldInterrupt( void );
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82 static unsigned long prvProcessTickInterrupt( void );
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84 /*-----------------------------------------------------------*/
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86 /* The WIN32 simulator runs each task in a thread. The context switching is
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87 managed by the threads, so the task stack does not have to be managed directly,
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88 although the task stack is still used to hold an xThreadState structure this is
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89 the only thing it will ever hold. The structure indirectly maps the task handle
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90 to a thread handle. */
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93 /* Handle of the thread that executes the task. */
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98 /* Simulated interrupts waiting to be processed. This is a bit mask where each
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99 bit represents one interrupt, so a maximum of 32 interrupts can be simulated. */
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100 static volatile unsigned long ulPendingInterrupts = 0UL;
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102 /* An event used to inform the simulated interrupt processing thread (a high
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103 priority thread that simulated interrupt processing) that an interrupt is
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105 static void *pvInterruptEvent = NULL;
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107 /* Mutex used to protect all the simulated interrupt variables that are accessed
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108 by multiple threads. */
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109 static void *pvInterruptEventMutex = NULL;
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111 /* The critical nesting count for the currently executing task. This is
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112 initialised to a non-zero value so interrupts do not become enabled during
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113 the initialisation phase. As each task has its own critical nesting value
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114 ulCriticalNesting will get set to zero when the first task runs. This
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115 initialisation is probably not critical in this simulated environment as the
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116 simulated interrupt handlers do not get created until the FreeRTOS scheduler is
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118 static unsigned long ulCriticalNesting = 9999UL;
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120 /* Handlers for all the simulated software interrupts. The first two positions
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121 are used for the Yield and Tick interrupts so are handled slightly differently,
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122 all the other interrupts can be user defined. */
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123 static unsigned long (*ulIsrHandler[ portMAX_INTERRUPTS ])( void ) = { 0 };
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125 /* Pointer to the TCB of the currently executing task. */
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126 extern void *pxCurrentTCB;
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128 /*-----------------------------------------------------------*/
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130 static DWORD WINAPI prvSimulatedPeripheralTimer( LPVOID lpParameter )
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132 portTickType xMinimumWindowsBlockTime = ( portTickType ) 20;
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134 /* Just to prevent compiler warnings. */
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135 ( void ) lpParameter;
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139 /* Wait until the timer expires and we can access the simulated interrupt
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140 variables. *NOTE* this is not a 'real time' way of generating tick
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141 events as the next wake time should be relative to the previous wake
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142 time, not the time that Sleep() is called. It is done this way to
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143 prevent overruns in this very non real time simulated/emulated
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145 if( portTICK_RATE_MS < xMinimumWindowsBlockTime )
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147 Sleep( xMinimumWindowsBlockTime );
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151 Sleep( portTICK_RATE_MS );
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154 WaitForSingleObject( pvInterruptEventMutex, INFINITE );
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156 /* The timer has expired, generate the simulated tick event. */
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157 ulPendingInterrupts |= ( 1 << portINTERRUPT_TICK );
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159 /* The interrupt is now pending - notify the simulated interrupt
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161 SetEvent( pvInterruptEvent );
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163 /* Give back the mutex so the simulated interrupt handler unblocks
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164 and can access the interrupt handler variables. */
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165 ReleaseMutex( pvInterruptEventMutex );
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169 /* Should never reach here - MingW complains if you leave this line out,
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170 MSVC complains if you put it in. */
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174 /*-----------------------------------------------------------*/
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176 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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178 xThreadState *pxThreadState = NULL;
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180 /* In this simulated case a stack is not initialised, but instead a thread
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181 is created that will execute the task being created. The thread handles
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182 the context switching itself. The xThreadState object is placed onto
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183 the stack that was created for the task - so the stack buffer is still
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184 used, just not in the conventional way. It will not be used for anything
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185 other than holding this structure. */
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186 pxThreadState = ( xThreadState * ) ( pxTopOfStack - sizeof( xThreadState ) );
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188 /* Create the thread itself. */
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189 pxThreadState->pvThread = CreateThread( NULL, 0, ( LPTHREAD_START_ROUTINE ) pxCode, pvParameters, CREATE_SUSPENDED, NULL );
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190 SetThreadAffinityMask( pxThreadState->pvThread, 0x01 );
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191 SetThreadPriorityBoost( pxThreadState->pvThread, TRUE );
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192 SetThreadPriority( pxThreadState->pvThread, THREAD_PRIORITY_IDLE );
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194 return ( portSTACK_TYPE * ) pxThreadState;
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196 /*-----------------------------------------------------------*/
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198 portBASE_TYPE xPortStartScheduler( void )
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201 long lSuccess = pdPASS;
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202 xThreadState *pxThreadState;
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204 /* Install the interrupt handlers used by the scheduler itself. */
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205 vPortSetInterruptHandler( portINTERRUPT_YIELD, prvProcessYieldInterrupt );
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206 vPortSetInterruptHandler( portINTERRUPT_TICK, prvProcessTickInterrupt );
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207 vPortSetInterruptHandler( portINTERRUPT_DELETE_THREAD, prvProcessDeleteThreadInterrupt );
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209 /* Create the events and mutexes that are used to synchronise all the
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211 pvInterruptEventMutex = CreateMutex( NULL, FALSE, NULL );
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212 pvInterruptEvent = CreateEvent( NULL, FALSE, FALSE, NULL );
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214 if( ( pvInterruptEventMutex == NULL ) || ( pvInterruptEvent == NULL ) )
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219 /* Set the priority of this thread such that it is above the priority of
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220 the threads that run tasks. This higher priority is required to ensure
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221 simulated interrupts take priority over tasks. */
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222 pvHandle = GetCurrentThread();
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223 if( pvHandle == NULL )
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228 if( lSuccess == pdPASS )
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230 if( SetThreadPriority( pvHandle, THREAD_PRIORITY_NORMAL ) == 0 )
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234 SetThreadPriorityBoost( pvHandle, TRUE );
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235 SetThreadAffinityMask( pvHandle, 0x01 );
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238 if( lSuccess == pdPASS )
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240 /* Start the thread that simulates the timer peripheral to generate
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241 tick interrupts. The priority is set below that of the simulated
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242 interrupt handler so the interrupt event mutex is used for the
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243 handshake / overrun protection. */
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244 pvHandle = CreateThread( NULL, 0, prvSimulatedPeripheralTimer, NULL, 0, NULL );
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245 if( pvHandle != NULL )
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247 SetThreadPriority( pvHandle, THREAD_PRIORITY_BELOW_NORMAL );
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248 SetThreadPriorityBoost( pvHandle, TRUE );
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249 SetThreadAffinityMask( pvHandle, 0x01 );
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252 /* Start the highest priority task by obtaining its associated thread
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253 state structure, in which is stored the thread handle. */
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254 pxThreadState = ( xThreadState * ) *( ( unsigned long * ) pxCurrentTCB );
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255 ulCriticalNesting = portNO_CRITICAL_NESTING;
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257 /* Bump up the priority of the thread that is going to run, in the
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258 hope that this will asist in getting the Windows thread scheduler to
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259 behave as an embedded engineer might expect. */
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260 ResumeThread( pxThreadState->pvThread );
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262 /* Handle all simulated interrupts - including yield requests and
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263 simulated ticks. */
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264 prvProcessSimulatedInterrupts();
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267 /* Would not expect to return from prvProcessSimulatedInterrupts(), so should
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271 /*-----------------------------------------------------------*/
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273 static unsigned long prvProcessDeleteThreadInterrupt( void )
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277 /*-----------------------------------------------------------*/
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279 static unsigned long prvProcessYieldInterrupt( void )
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283 /*-----------------------------------------------------------*/
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285 static unsigned long prvProcessTickInterrupt( void )
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287 unsigned long ulSwitchRequired;
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289 /* Process the tick itself. */
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290 vTaskIncrementTick();
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291 #if( configUSE_PREEMPTION != 0 )
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293 /* A context switch is only automatically performed from the tick
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294 interrupt if the pre-emptive scheduler is being used. */
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295 ulSwitchRequired = pdTRUE;
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299 ulSwitchRequired = pdFALSE;
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303 return ulSwitchRequired;
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305 /*-----------------------------------------------------------*/
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307 static void prvProcessSimulatedInterrupts( void )
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309 unsigned long ulSwitchRequired, i;
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310 xThreadState *pxThreadState;
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311 void *pvObjectList[ 2 ];
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313 /* Going to block on the mutex that ensured exclusive access to the simulated
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314 interrupt objects, and the event that signals that a simulated interrupt
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315 should be processed. */
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316 pvObjectList[ 0 ] = pvInterruptEventMutex;
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317 pvObjectList[ 1 ] = pvInterruptEvent;
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321 WaitForMultipleObjects( sizeof( pvObjectList ) / sizeof( void * ), pvObjectList, TRUE, INFINITE );
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323 /* Used to indicate whether the simulated interrupt processing has
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324 necessitated a context switch to another task/thread. */
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325 ulSwitchRequired = pdFALSE;
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327 /* For each interrupt we are interested in processing, each of which is
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328 represented by a bit in the 32bit ulPendingInterrupts variable. */
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329 for( i = 0; i < portMAX_INTERRUPTS; i++ )
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331 /* Is the simulated interrupt pending? */
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332 if( ulPendingInterrupts & ( 1UL << i ) )
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334 /* Is a handler installed? */
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335 if( ulIsrHandler[ i ] != NULL )
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337 /* Run the actual handler. */
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338 if( ulIsrHandler[ i ]() != pdFALSE )
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340 ulSwitchRequired |= ( 1 << i );
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344 /* Clear the interrupt pending bit. */
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345 ulPendingInterrupts &= ~( 1UL << i );
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349 if( ulSwitchRequired != pdFALSE )
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351 void *pvOldCurrentTCB;
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353 pvOldCurrentTCB = pxCurrentTCB;
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355 /* Select the next task to run. */
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356 vTaskSwitchContext();
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358 /* If the task selected to enter the running state is not the task
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359 that is already in the running state. */
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360 if( pvOldCurrentTCB != pxCurrentTCB )
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362 /* Suspend the old thread. */
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363 pxThreadState = ( xThreadState *) *( ( unsigned long * ) pvOldCurrentTCB );
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365 if( ( ulSwitchRequired & ( 1 << portINTERRUPT_DELETE_THREAD ) ) != pdFALSE )
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367 TerminateThread( pxThreadState->pvThread, 0 );
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371 SuspendThread( pxThreadState->pvThread );
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374 /* Obtain the state of the task now selected to enter the
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376 pxThreadState = ( xThreadState * ) ( *( unsigned long *) pxCurrentTCB );
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377 ResumeThread( pxThreadState->pvThread );
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381 ReleaseMutex( pvInterruptEventMutex );
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384 /*-----------------------------------------------------------*/
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386 void vPortDeleteThread( void *pvTaskToDelete )
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388 xThreadState *pxThreadState;
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390 if( pvTaskToDelete == pxCurrentTCB )
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392 /* The task is deleting itself, and so the thread that is running now
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393 is also to be deleted. This has to be deferred until this thread is
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394 no longer running, so its done in the simulated interrupt handler thread. */
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395 vPortGenerateSimulatedInterrupt( portINTERRUPT_DELETE_THREAD );
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399 WaitForSingleObject( pvInterruptEventMutex, INFINITE );
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401 /* Find the handle of the thread being deleted. */
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402 pxThreadState = ( xThreadState * ) ( *( unsigned long *) pvTaskToDelete );
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403 TerminateThread( pxThreadState->pvThread, 0 );
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405 ReleaseMutex( pvInterruptEventMutex );
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408 /*-----------------------------------------------------------*/
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410 void vPortEndScheduler( void )
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412 /* This function IS NOT TESTED! */
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413 TerminateProcess( GetCurrentProcess(), 0 );
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415 /*-----------------------------------------------------------*/
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417 void vPortGenerateSimulatedInterrupt( unsigned long ulInterruptNumber )
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419 xThreadState *pxThreadState;
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421 if( ( ulInterruptNumber < portMAX_INTERRUPTS ) && ( pvInterruptEventMutex != NULL ) )
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423 /* Yield interrupts are processed even when critical nesting is non-zero. */
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424 WaitForSingleObject( pvInterruptEventMutex, INFINITE );
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425 ulPendingInterrupts |= ( 1 << ulInterruptNumber );
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427 /* The simulated interrupt is now held pending, but don't actually process it
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428 yet if this call is within a critical section. It is possible for this to
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429 be in a critical section as calls to wait for mutexes are accumulative. */
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430 if( ulCriticalNesting == 0 )
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432 /* The event handler needs to know to signal the interrupt acknowledge event
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433 the next time this task runs. */
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434 pxThreadState = ( xThreadState * ) *( ( unsigned long * ) pxCurrentTCB );
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435 SetEvent( pvInterruptEvent );
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438 ReleaseMutex( pvInterruptEventMutex );
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441 /*-----------------------------------------------------------*/
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443 void vPortSetInterruptHandler( unsigned long ulInterruptNumber, unsigned long (*pvHandler)( void ) )
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445 if( ulInterruptNumber < portMAX_INTERRUPTS )
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447 if( pvInterruptEventMutex != NULL )
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449 WaitForSingleObject( pvInterruptEventMutex, INFINITE );
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450 ulIsrHandler[ ulInterruptNumber ] = pvHandler;
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451 ReleaseMutex( pvInterruptEventMutex );
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455 ulIsrHandler[ ulInterruptNumber ] = pvHandler;
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459 /*-----------------------------------------------------------*/
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461 void vPortEnterCritical( void )
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463 if( xTaskGetSchedulerState() != taskSCHEDULER_NOT_STARTED )
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465 /* The interrupt event mutex is held for the entire critical section,
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466 effectively disabling (simulated) interrupts. */
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467 WaitForSingleObject( pvInterruptEventMutex, INFINITE );
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468 ulCriticalNesting++;
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472 ulCriticalNesting++;
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475 /*-----------------------------------------------------------*/
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477 void vPortExitCritical( void )
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479 xThreadState *pxThreadState;
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480 long lMutexNeedsReleasing;
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482 /* The interrupt event mutex should already be held by this thread as it was
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483 obtained on entry to the critical section. */
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485 lMutexNeedsReleasing = pdTRUE;
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487 if( ulCriticalNesting > portNO_CRITICAL_NESTING )
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489 if( ulCriticalNesting == ( portNO_CRITICAL_NESTING + 1 ) )
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491 ulCriticalNesting--;
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493 /* Were any interrupts set to pending while interrupts were
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494 (simulated) disabled? */
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495 if( ulPendingInterrupts != 0UL )
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497 SetEvent( pvInterruptEvent );
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499 /* The event handler needs to know to signal the interrupt
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500 acknowledge event the next time this task runs. */
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501 pxThreadState = ( xThreadState * ) *( ( unsigned long * ) pxCurrentTCB );
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503 /* Mutex will be released now, so does not require releasing
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504 on function exit. */
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505 lMutexNeedsReleasing = pdFALSE;
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506 ReleaseMutex( pvInterruptEventMutex );
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511 /* Tick interrupts will still not be processed as the critical
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512 nesting depth will not be zero. */
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513 ulCriticalNesting--;
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517 if( lMutexNeedsReleasing == pdTRUE )
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519 ReleaseMutex( pvInterruptEventMutex );
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522 /*-----------------------------------------------------------*/
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