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Fix SMP task self void run state change (FreeRTOS#984)
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* Request a task to yield after been suspended or deleted to prevent this task puts itself back to another list
* Fix volatile variable access order to ensure ensure compliance with MISRA C 2012 Rule 13.5

---------

Signed-off-by: Gaurav Aggarwal <[email protected]>
Co-authored-by: Gaurav Aggarwal <[email protected]>
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@chinglee-iot @aggarg
chinglee-iot and aggarg authored Feb 6, 2024
1 parent 23afc48 commit 57a5ed7
Showing 1 changed file with 87 additions and 76 deletions.
163 changes: 87 additions & 76 deletions tasks.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2191,6 +2191,7 @@ static void prvInitialiseNewTask( TaskFunction_t pxTaskCode,
{
TCB_t * pxTCB;
BaseType_t xDeleteTCBInIdleTask = pdFALSE;
BaseType_t xTaskIsRunningOrYielding;

traceENTER_vTaskDelete( xTaskToDelete );

Expand Down Expand Up @@ -2226,10 +2227,15 @@ static void prvInitialiseNewTask( TaskFunction_t pxTaskCode,
* not return. */
uxTaskNumber++;

/* Use temp variable as distinct sequence points for reading volatile
* variables prior to a logical operator to ensure compliance with
* MISRA C 2012 Rule 13.5. */
xTaskIsRunningOrYielding = taskTASK_IS_RUNNING_OR_SCHEDULED_TO_YIELD( pxTCB );

/* If the task is running (or yielding), we must add it to the
* termination list so that an idle task can delete it when it is
* no longer running. */
if( ( xSchedulerRunning != pdFALSE ) && ( taskTASK_IS_RUNNING_OR_SCHEDULED_TO_YIELD( pxTCB ) != pdFALSE ) )
if( ( xSchedulerRunning != pdFALSE ) && ( xTaskIsRunningOrYielding != pdFALSE ) )
{
/* A running task or a task which is scheduled to yield is being
* deleted. This cannot complete when the task is still running
Expand Down Expand Up @@ -2261,6 +2267,30 @@ static void prvInitialiseNewTask( TaskFunction_t pxTaskCode,
#else
portPRE_TASK_DELETE_HOOK( pxTCB, &( xYieldPendings[ pxTCB->xTaskRunState ] ) );
#endif

/* In the case of SMP, it is possible that the task being deleted
* is running on another core. We must evict the task before
* exiting the critical section to ensure that the task cannot
* take an action which puts it back on ready/state/event list,
* thereby nullifying the delete operation. Once evicted, the
* task won't be scheduled ever as it will no longer be on the
* ready list. */
#if ( configNUMBER_OF_CORES > 1 )
{
if( taskTASK_IS_RUNNING( pxTCB ) == pdTRUE )
{
if( pxTCB->xTaskRunState == ( BaseType_t ) portGET_CORE_ID() )
{
configASSERT( uxSchedulerSuspended == 0 );
taskYIELD_WITHIN_API();
}
else
{
prvYieldCore( pxTCB->xTaskRunState );
}
}
}
#endif /* #if ( configNUMBER_OF_CORES > 1 ) */
}
else
{
Expand All @@ -2284,9 +2314,9 @@ static void prvInitialiseNewTask( TaskFunction_t pxTaskCode,

/* Force a reschedule if it is the currently running task that has just
* been deleted. */
if( xSchedulerRunning != pdFALSE )
#if ( configNUMBER_OF_CORES == 1 )
{
#if ( configNUMBER_OF_CORES == 1 )
if( xSchedulerRunning != pdFALSE )
{
if( pxTCB == pxCurrentTCB )
{
Expand All @@ -2298,30 +2328,8 @@ static void prvInitialiseNewTask( TaskFunction_t pxTaskCode,
mtCOVERAGE_TEST_MARKER();
}
}
#else /* #if ( configNUMBER_OF_CORES == 1 ) */
{
/* It is important to use critical section here because
* checking run state of a task must be done inside a
* critical section. */
taskENTER_CRITICAL();
{
if( taskTASK_IS_RUNNING( pxTCB ) == pdTRUE )
{
if( pxTCB->xTaskRunState == ( BaseType_t ) portGET_CORE_ID() )
{
configASSERT( uxSchedulerSuspended == 0 );
taskYIELD_WITHIN_API();
}
else
{
prvYieldCore( pxTCB->xTaskRunState );
}
}
}
taskEXIT_CRITICAL();
}
#endif /* #if ( configNUMBER_OF_CORES == 1 ) */
}
#endif /* #if ( configNUMBER_OF_CORES == 1 ) */

traceRETURN_vTaskDelete();
}
Expand Down Expand Up @@ -3155,26 +3163,66 @@ static void prvInitialiseNewTask( TaskFunction_t pxTaskCode,
}
}
#endif /* if ( configUSE_TASK_NOTIFICATIONS == 1 ) */
}
taskEXIT_CRITICAL();

if( xSchedulerRunning != pdFALSE )
{
/* Reset the next expected unblock time in case it referred to the
* task that is now in the Suspended state. */
taskENTER_CRITICAL();
/* In the case of SMP, it is possible that the task being suspended
* is running on another core. We must evict the task before
* exiting the critical section to ensure that the task cannot
* take an action which puts it back on ready/state/event list,
* thereby nullifying the suspend operation. Once evicted, the
* task won't be scheduled before it is resumed as it will no longer
* be on the ready list. */
#if ( configNUMBER_OF_CORES > 1 )
{
prvResetNextTaskUnblockTime();
if( xSchedulerRunning != pdFALSE )
{
/* Reset the next expected unblock time in case it referred to the
* task that is now in the Suspended state. */
prvResetNextTaskUnblockTime();

if( taskTASK_IS_RUNNING( pxTCB ) == pdTRUE )
{
if( pxTCB->xTaskRunState == ( BaseType_t ) portGET_CORE_ID() )
{
/* The current task has just been suspended. */
configASSERT( uxSchedulerSuspended == 0 );
vTaskYieldWithinAPI();
}
else
{
prvYieldCore( pxTCB->xTaskRunState );
}
}
else
{
mtCOVERAGE_TEST_MARKER();
}
}
else
{
mtCOVERAGE_TEST_MARKER();
}
}
taskEXIT_CRITICAL();
}
else
{
mtCOVERAGE_TEST_MARKER();
#endif /* #if ( configNUMBER_OF_CORES > 1 ) */
}
taskEXIT_CRITICAL();

#if ( configNUMBER_OF_CORES == 1 )
{
if( xSchedulerRunning != pdFALSE )
{
/* Reset the next expected unblock time in case it referred to the
* task that is now in the Suspended state. */
taskENTER_CRITICAL();
{
prvResetNextTaskUnblockTime();
}
taskEXIT_CRITICAL();
}
else
{
mtCOVERAGE_TEST_MARKER();
}

if( pxTCB == pxCurrentTCB )
{
if( xSchedulerRunning != pdFALSE )
Expand Down Expand Up @@ -3207,43 +3255,6 @@ static void prvInitialiseNewTask( TaskFunction_t pxTaskCode,
mtCOVERAGE_TEST_MARKER();
}
}
#else /* #if ( configNUMBER_OF_CORES == 1 ) */
{
/* Enter critical section here to check run state of a task. */
taskENTER_CRITICAL();
{
if( taskTASK_IS_RUNNING( pxTCB ) == pdTRUE )
{
if( xSchedulerRunning != pdFALSE )
{
if( pxTCB->xTaskRunState == ( BaseType_t ) portGET_CORE_ID() )
{
/* The current task has just been suspended. */
configASSERT( uxSchedulerSuspended == 0 );
vTaskYieldWithinAPI();
}
else
{
prvYieldCore( pxTCB->xTaskRunState );
}
}
else
{
/* This code path is not possible because only Idle tasks are
* assigned a core before the scheduler is started ( i.e.
* taskTASK_IS_RUNNING is only true for idle tasks before
* the scheduler is started ) and idle tasks cannot be
* suspended. */
mtCOVERAGE_TEST_MARKER();
}
}
else
{
mtCOVERAGE_TEST_MARKER();
}
}
taskEXIT_CRITICAL();
}
#endif /* #if ( configNUMBER_OF_CORES == 1 ) */

traceRETURN_vTaskSuspend();
Expand Down

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