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Continue adding some tick interrupt overflow protection to the timers module. This is not tested yet and still a work in progress.

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pull/4/head
Richard Barry 14 years ago
parent 7ee534e4c2
commit 3ba433ed39
1 changed files with 134 additions and 54 deletions
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188
Source/timers.c
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@ -1,8 +1,3 @@
/* Need to consider the switching of timer lists, and the placement of tasks into
the current and overflow timer lists very carefully. For example, should the
assessment as to which list a timer should be inserted into be relative the the
tick count at the timer, or the tick count when the timer task unblocked, etc. */
/*
FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.
@ -87,7 +82,7 @@ queue. */
typedef struct tmrTimerQueueMessage
{
portBASE_TYPE xMessageID; /*<< The command being sent to the timer service task. */
portTickType xMessageValue; /*<< An optional value used by a subset of commands, for example, when chaning the period of a timer. */
portTickType xMessageValue; /*<< An optional value used by a subset of commands, for example, when changing the period of a timer. */
xTIMER * pxTimer; /*<< The timer to which the command will be applied. */
} xTIMER_MESSAGE;
@ -106,7 +101,7 @@ PRIVILEGED_DATA static xQueueHandle xTimerQueue = NULL;
/*-----------------------------------------------------------*/
/*
* Initialise the infrustructure used by the timer service task if it has not
* Initialise the infrastructure used by the timer service task if it has not
* been initialised already.
*/
static void prvCheckForValidListAndQueue( void ) PRIVILEGED_FUNCTION;
@ -122,13 +117,25 @@ static void prvTimerTask( void *pvParameters ) PRIVILEGED_FUNCTION;
* Called by the timer service task to interpret and process a command it
* received on the timer queue.
*/
static void prvProcessReceivedCommands( void ) PRIVILEGED_FUNCTION;
static void prvProcessReceivedCommands( portTickType xAssumedTimeNow ) PRIVILEGED_FUNCTION;
/*
* Insert the timer into either xActiveTimerList1, or xActiveTimerList2,
* depending on if the expire time causes a timer counter overflow.
*/
static void prvInsertTimerInActiveList( xTIMER *pxTimer, portTickType xNextExpiryTime );
static void prvInsertTimerInActiveList( xTIMER *pxTimer, portTickType xNextExpiryTime, portTickType xAssumedTimeNow ) PRIVILEGED_FUNCTION;
/*
* An active timer has reached its expire time. Reload the timer if it is an
* auto reload timer, then call its callback.
*/
static void prvProcessExpiredTimer( portTickType xNextExpireTime, portTickType xAssumedTimeNow ) PRIVILEGED_FUNCTION;
/*
* The tick count has overflowed. Switch the timer lists after ensuring the
* current timer list does not still reference some timers.
*/
static void prvSwitchTimerLists( portTickType xAssumedTimeNow ) PRIVILEGED_FUNCTION;
/*-----------------------------------------------------------*/
@ -137,7 +144,7 @@ portBASE_TYPE xTimerCreateTimerTask( void )
portBASE_TYPE xReturn = pdFAIL;
/* This function is called when the scheduler is started if
configUSE_TIMERS is set to 1. Check that the infrustructure used by the
configUSE_TIMERS is set to 1. Check that the infrastructure used by the
timer service task has been created/initialised. If timers have already
been created then the initialisation will already have been performed. */
prvCheckForValidListAndQueue();
@ -159,7 +166,7 @@ xTIMER *pxNewTimer;
pxNewTimer = ( xTIMER * ) pvPortMalloc( sizeof( xTIMER ) );
if( pxNewTimer != NULL )
{
/* Ensure the infrustructure used by the timer service task has been
/* Ensure the infrastructure used by the timer service task has been
created/initialised. */
prvCheckForValidListAndQueue();
@ -204,21 +211,53 @@ xTIMER_MESSAGE xMessage;
}
/*-----------------------------------------------------------*/
static void prvTimerTask( void *pvParameters )
static void prvProcessExpiredTimer( portTickType xNextExpireTime, portTickType xAssumedTimeNow )
{
portTickType xNextExpireTime, xTimeNow;
xTIMER *pxTimer;
if( listLIST_IS_EMPTY( pxCurrentTimerList ) == pdFALSE )
{
/* Remove the timer from the list of active timers. */
pxTimer = ( xTIMER * ) listGET_OWNER_OF_HEAD_ENTRY( pxCurrentTimerList );
vListRemove( &( pxTimer->xTimerListItem ) );
/* If the timer is an auto reload timer then calculate the next
expiry time and re-insert the timer in the list of active timers. */
if( pxTimer->uxAutoReload == pdTRUE )
{
/* This is the only time a timer is inserted into a list using
a time relative to anything other than the current time. It
will therefore be inserted into the correct list relative to
the time this task thinks it is now, even if a command to
switch lists due to a tick count overflow is already waiting in
the timer queue. */
prvInsertTimerInActiveList( pxTimer, ( xNextExpireTime + pxTimer->xTimerPeriodInTicks ), xAssumedTimeNow );
}
/* Call the timer callback. */
pxTimer->pxCallbackFunction( ( xTimerHandle ) pxTimer );
}
}
/*-----------------------------------------------------------*/
static void prvTimerTask( void *pvParameters )
{
portTickType xNextExpireTime, xTimeNow, xFrozenTimeNow;
/* Just to avoid compiler warnings. */
( void ) pvParameters;
for( ;; )
{
/* Take a snapshot of the time to use while assessing expiry and auto
reload times. */
xFrozenTimeNow = xTaskGetTickCount();
/* Timers are listed in expiry time order, with the head of the list
referencing the task that will expire first. Obtain the time at which
the timer with the nearest expiry time will expire. If there are no
active timers then just set the next expire time to the maximum possible
time to ensure this task does not run unnecessarily. */
time to ensure this task does not run unnecessarily. */
if( listLIST_IS_EMPTY( pxCurrentTimerList ) == pdFALSE )
{
xNextExpireTime = listGET_ITEM_VALUE_OF_HEAD_ENTRY( pxCurrentTimerList );
@ -228,58 +267,72 @@ xTIMER *pxTimer;
xNextExpireTime = portMAX_DELAY;
}
/* Has the timer expired? */
if( xNextExpireTime <= xTaskGetTickCount() )
/* Has the timer expired? This expiry time is relative to the snapshot
of the time taken to be used in this loop iteration - so it doesn't
matter at this point if a tick count overflows here. */
if( xNextExpireTime <= xFrozenTimeNow )
{
/* Remove the timer from the list of active timers. */
pxTimer = listGET_OWNER_OF_HEAD_ENTRY( pxCurrentTimerList );
vListRemove( &( pxTimer->xTimerListItem ) );
/* If the timer is an autoreload timer then calculate the next
expiry time and re-insert the timer in the list of active timers. */
if( pxTimer->uxAutoReload == pdTRUE )
{
prvInsertTimerInActiveList( pxTimer, ( xNextExpireTime + pxTimer->xTimerPeriodInTicks ) );
}
/* Call the timer callback. */
pxTimer->pxCallbackFunction( ( xTimerHandle ) pxTimer );
prvProcessExpiredTimer( xNextExpireTime, xFrozenTimeNow );
}
else
{
/* Block this task until the next timer expires, or a command is
received. */
taskENTER_CRITICAL();
vTaskSuspendAll();
{
/* Has the tick overflowed since a time snapshot was taken? */
xTimeNow = xTaskGetTickCount();
if( xTimeNow < xNextExpireTime )
if( xTimeNow >= xFrozenTimeNow )
{
/* Has the expire not still not been met? The tick count
may be greater now than when the time snapshot was taken. */
if( xNextExpireTime <= xTimeNow )
{
prvProcessExpiredTimer( xNextExpireTime, xFrozenTimeNow );
}
else
{
/* The tick count has not overflowed since the time
snapshot, and the next expire time has not been reached
since the last snapshot was taken. This task should
therefore block to wait for the next expire time. */
vQueueWaitForMessageRestricted( xTimerQueue, ( xNextExpireTime - xTimeNow ) );
}
}
else
{
/* This is a simple fast function - a yield will not be
performed until after this critical section exits. */
vQueueWaitForMessageRestricted( xTimerQueue, ( xNextExpireTime - xTimeNow ) );
/* The tick count has overflowed since the time snapshot
was taken, therefore, the task should not block but continue
with another loop. The command queue should contain a
command to switch lists. */
}
}
taskEXIT_CRITICAL();
if( xTaskResumeAll() == pdFALSE )
{
/* Yield to wait for either a command to arrive, or the block time
to expire. If a command arrived between the critical section being
exited and this yield then the yield will just return to the same
task. */
portYIELD_WITHIN_API();
}
/* Yield to wait for either a command to arrive, or the block time
to expire. If a command arrived between the critical section being
exited and this yeild then the yield will just return to the same
task. */
portYIELD_WITHIN_API();
/* Take a snapshot of the time now for use in this iteration of the
task loop. */
xFrozenTimeNow = xTaskGetTickCount();
/* Empty the command queue, if it contains any commands. */
prvProcessReceivedCommands();
prvProcessReceivedCommands( xFrozenTimeNow );
}
}
}
/*-----------------------------------------------------------*/
static void prvInsertTimerInActiveList( xTIMER *pxTimer, portTickType xNextExpiryTime )
static void prvInsertTimerInActiveList( xTIMER *pxTimer, portTickType xNextExpiryTime, portTickType xAssumedTimeNow )
{
listSET_LIST_ITEM_VALUE( &( pxTimer->xTimerListItem ), xNextExpiryTime );
listSET_LIST_ITEM_OWNER( &( pxTimer->xTimerListItem ), pxTimer );
if( xNextExpiryTime < xTaskGetTickCount() )
if( xNextExpiryTime < xAssumedTimeNow )
{
vListInsert( pxOverflowTimerList, &( pxTimer->xTimerListItem ) );
}
@ -290,24 +343,24 @@ static void prvInsertTimerInActiveList( xTIMER *pxTimer, portTickType xNextExpir
}
/*-----------------------------------------------------------*/
static void prvProcessReceivedCommands( void )
static void prvProcessReceivedCommands( portTickType xAssumedTimeNow )
{
xTIMER_MESSAGE xMessage;
xTIMER *pxTimer;
xList *pxTemp;
portBASE_TYPE xSwitchListsOnExit = pdFALSE;
while( xQueueReceive( xTimerQueue, &xMessage, tmrNO_DELAY ) != pdFAIL )
{
pxTimer = xMessage.pxTimer;
/* Is the timer already in the list of active timers? When the command
/* Is the timer already in a list of active timers? When the command
is trmCOMMAND_PROCESS_TIMER_OVERFLOW, the timer will be NULL as the
command is to the task rather than to an individual timer. */
if( pxTimer != NULL )
{
if( listIS_CONTAINED_WITHIN( NULL, &( pxTimer->xTimerListItem ) ) == pdFALSE )
{
/* The timer is in the list, remove it. */
/* The timer is in a list, remove it. */
vListRemove( &( pxTimer->xTimerListItem ) );
}
}
@ -316,7 +369,7 @@ xList *pxTemp;
{
case tmrCOMMAND_START :
/* Start or restart a timer. */
prvInsertTimerInActiveList( pxTimer, xTaskGetTickCount() + pxTimer->xTimerPeriodInTicks );
prvInsertTimerInActiveList( pxTimer, xAssumedTimeNow + pxTimer->xTimerPeriodInTicks, xAssumedTimeNow );
break;
case tmrCOMMAND_STOP :
@ -326,7 +379,7 @@ xList *pxTemp;
case tmrCOMMAND_CHANGE_PERIOD :
pxTimer->xTimerPeriodInTicks = xMessage.xMessageValue;
prvInsertTimerInActiveList( pxTimer, ( xTaskGetTickCount() + pxTimer->xTimerPeriodInTicks ) );
prvInsertTimerInActiveList( pxTimer, ( xAssumedTimeNow + pxTimer->xTimerPeriodInTicks ), xAssumedTimeNow );
break;
case tmrCOMMAND_DELETE :
@ -336,11 +389,9 @@ xList *pxTemp;
break;
case trmCOMMAND_PROCESS_TIMER_OVERFLOW :
/* The tick count has overflowed. The timer lists must be
switched. */
pxTemp = pxCurrentTimerList;
pxCurrentTimerList = pxOverflowTimerList;
pxOverflowTimerList = pxTemp;
/* Hold this pending until all the other messages have been
processed. */
xSwitchListsOnExit = pdTRUE;
break;
default :
@ -348,6 +399,32 @@ xList *pxTemp;
break;
}
}
if( xSwitchListsOnExit == pdTRUE )
{
prvSwitchTimerLists( xAssumedTimeNow );
}
}
/*-----------------------------------------------------------*/
static void prvSwitchTimerLists( portTickType xAssumedTimeNow )
{
portTickType xNextExpireTime;
xList *pxTemp;
/* The tick count has overflowed. The timer lists must be switched.
If there are any timers still referenced from the current timer list
then they must have expired and should be processed before the lists
are switched. */
while( listLIST_IS_EMPTY( pxCurrentTimerList ) == pdFALSE )
{
xNextExpireTime = listGET_ITEM_VALUE_OF_HEAD_ENTRY( pxCurrentTimerList );
prvProcessExpiredTimer( xNextExpireTime, xAssumedTimeNow );
}
pxTemp = pxCurrentTimerList;
pxCurrentTimerList = pxOverflowTimerList;
pxOverflowTimerList = pxTemp;
}
/*-----------------------------------------------------------*/
@ -398,3 +475,6 @@ xTIMER *pxTimer = ( xTIMER * ) xTimer;
}
/*-----------------------------------------------------------*/

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