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楼主 |
发表于 2015-8-3 09:19:37
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freeOS里的空闲任务
/*
* -----------------------------------------------------------
* The Idle task.
* ----------------------------------------------------------
*
* The portTASK_FUNCTION() macro is used to allow port/compiler specific
* language extensions. The equivalent prototype for this function is:
*
* void prvIdleTask( void *pvParameters );
*
*/
static portTASK_FUNCTION( prvIdleTask, pvParameters )
{
/* Stop warnings. */
( void ) pvParameters;
for( ;; )
{
/* See if any tasks have been deleted. */
prvCheckTasksWaitingTermination();
#if ( configUSE_PREEMPTION == 0 )
{
/* If we are not using preemption we keep forcing a task switch to
see if any other task has become available. If we are using
preemption we don't need to do this as any task becoming available
will automatically get the processor anyway. */
taskYIELD();
}
#endif /* configUSE_PREEMPTION */
#if ( ( configUSE_PREEMPTION == 1 ) && ( configIDLE_SHOULD_YIELD == 1 ) )
{
/* When using preemption tasks of equal priority will be
timesliced. If a task that is sharing the idle priority is ready
to run then the idle task should yield before the end of the
timeslice.
A critical region is not required here as we are just reading from
the list, and an occasional incorrect value will not matter. If
the ready list at the idle priority contains more than one task
then a task other than the idle task is ready to execute. */
if( listCURRENT_LIST_LENGTH( &( pxReadyTasksLists[ tskIDLE_PRIORITY ] ) ) > ( UBaseType_t ) 1 )
{
taskYIELD();
}
else
{
mtCOVERAGE_TEST_MARKER();
}
}
#endif /* ( ( configUSE_PREEMPTION == 1 ) && ( configIDLE_SHOULD_YIELD == 1 ) ) */
#if ( configUSE_IDLE_HOOK == 1 )
{
extern void vApplicationIdleHook( void );
/* Call the user defined function from within the idle task. This
allows the application designer to add background functionality
without the overhead of a separate task.
NOTE: vApplicationIdleHook() MUST NOT, UNDER ANY CIRCUMSTANCES,
CALL A FUNCTION THAT MIGHT BLOCK. */
vApplicationIdleHook();
}
#endif /* configUSE_IDLE_HOOK */
/* This conditional compilation should use inequality to 0, not equality
to 1. This is to ensure portSUPPRESS_TICKS_AND_SLEEP() is called when
user defined low power mode implementations require
configUSE_TICKLESS_IDLE to be set to a value other than 1. */
#if ( configUSE_TICKLESS_IDLE != 0 )
{
TickType_t xExpectedIdleTime;
/* It is not desirable to suspend then resume the scheduler on
each iteration of the idle task. Therefore, a preliminary
test of the expected idle time is performed without the
scheduler suspended. The result here is not necessarily
valid. */
xExpectedIdleTime = prvGetExpectedIdleTime();
if( xExpectedIdleTime >= configEXPECTED_IDLE_TIME_BEFORE_SLEEP )
{
vTaskSuspendAll();
{
/* Now the scheduler is suspended, the expected idle
time can be sampled again, and this time its value can
be used. */
configASSERT( xNextTaskUnblockTime >= xTickCount );
xExpectedIdleTime = prvGetExpectedIdleTime();
if( xExpectedIdleTime >= configEXPECTED_IDLE_TIME_BEFORE_SLEEP )
{
traceLOW_POWER_IDLE_BEGIN();
portSUPPRESS_TICKS_AND_SLEEP( xExpectedIdleTime );
traceLOW_POWER_IDLE_END();
}
else
{
mtCOVERAGE_TEST_MARKER();
}
}
( void ) xTaskResumeAll();
}
else
{
mtCOVERAGE_TEST_MARKER();
}
}
#endif /* configUSE_TICKLESS_IDLE */
}
} |
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发表于 2015-8-2 21:09:05
