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Add more comment for core affinity in prvSelectHighestPriorityTask (#801)

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* Add more comment for core affinity in prvSelectHighestPriorityTask

Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>

---------

Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
Co-authored-by: kar-rahul-aws <118818625+kar-rahul-aws@users.noreply.github.com>
Co-authored-by: Gaurav Aggarwal <aggarg@amazon.com>
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chinglee-iot 2023-10-05 15:39:24 +08:00 committed by GitHub
parent 317bc0c89c
commit 97d48ba94a
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1 changed files with 21 additions and 6 deletions
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tasks.c
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@ -1134,16 +1134,31 @@ static void prvAddNewTaskToReadyList( TCB_t * pxNewTCB ) PRIVILEGED_FUNCTION;
if( ( uxCoreMap & ( ( UBaseType_t ) 1U << ( UBaseType_t ) xCoreID ) ) != 0U )
{
/* The ready task that was removed from this core is not excluded from it.
* Only look at the intersection of the cores the removed task is allowed to run
* on with the cores that the new task is excluded from. It is possible that the
* new task was only placed onto this core because it is excluded from another.
* Check to see if the previous task could run on one of those cores. */
/* pxPreviousTCB was removed from this core and this core is not excluded
* from it's core affinity mask.
*
* pxPreviousTCB is preempted by the new higher priority task
* pxCurrentTCBs[ xCoreID ]. When searching a new core for pxPreviousTCB,
* we do not need to look at the cores on which pxCurrentTCBs[ xCoreID ]
* is allowed to run. The reason is - when more than one cores are
* eligible for an incoming task, we preempt the core with the minimum
* priority task. Because this core (i.e. xCoreID) was preempted for
* pxCurrentTCBs[ xCoreID ], this means that all the others cores
* where pxCurrentTCBs[ xCoreID ] can run, are running tasks with priority
* no lower than pxPreviousTCB's priority. Therefore, the only cores where
* which can be preempted for pxPreviousTCB are the ones where
* pxCurrentTCBs[ xCoreID ] is not allowed to run (and obviously,
* pxPreviousTCB is allowed to run).
*
* This is an optimization which reduces the number of cores needed to be
* searched for pxPreviousTCB to run. */
uxCoreMap &= ~( pxCurrentTCBs[ xCoreID ]->uxCoreAffinityMask );
}
else
{
/* The ready task that was removed from this core is excluded from it. */
/* pxPreviousTCB's core affinity mask is changed and it is no longer
* allowed to run on this core. Searching all the cores in pxPreviousTCB's
* new core affinity mask to find a core on which it can run. */
}
uxCoreMap &= ( ( 1U << configNUMBER_OF_CORES ) - 1U );