On Mon, Nov 15, 2021 at 10:13 AM Sebastian Huber
<sebastian.hu...@embedded-brains.de> wrote:
>
> If a node is moved from the scheduled chain to the ready queue, then we
> know that it is the highest priority ready node. So, it can be
> prepended to the ready queue without doing any comparisons.
>
I'm not certain on the logic here. It is possible for 2 threads X and
Y become ready simultaneously, such that:
X is higher priority than Y. X and Y are higher priority than Z. X
gets scheduled to replace Z, but there is no lower-priority/affine CPU
for Y to get scheduled, so Y will be ready. Then Z is not
higher-priority than Y so it shouldn't be directly prepended.
I think that could happen?
> Update #4531.
> ---
> cpukit/score/src/scheduleredfsmp.c | 20 +++++++++++++-------
> 1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/cpukit/score/src/scheduleredfsmp.c
> b/cpukit/score/src/scheduleredfsmp.c
> index 7da777e87a..27be08ac40 100644
> --- a/cpukit/score/src/scheduleredfsmp.c
> +++ b/cpukit/score/src/scheduleredfsmp.c
> @@ -374,15 +374,21 @@ static inline void
> _Scheduler_EDF_SMP_Move_from_scheduled_to_ready(
> Scheduler_Node *scheduled_to_ready
> )
> {
> - Priority_Control insert_priority;
> + Scheduler_EDF_SMP_Context *self;
> + Scheduler_EDF_SMP_Node *node;
> + uint8_t rqi;
> + Scheduler_EDF_SMP_Ready_queue *ready_queue;
>
> _Scheduler_EDF_SMP_Extract_from_scheduled( context, scheduled_to_ready );
> - insert_priority = _Scheduler_SMP_Node_priority( scheduled_to_ready );
> - _Scheduler_EDF_SMP_Insert_ready(
> - context,
> - scheduled_to_ready,
> - insert_priority
> - );
> +
> + self = _Scheduler_EDF_SMP_Get_self( context );
> + node = _Scheduler_EDF_SMP_Node_downcast( scheduled_to_ready );
> + rqi = node->ready_queue_index;
> + ready_queue = &self->Ready[ rqi ];
> +
> + _Scheduler_EDF_SMP_Activate_ready_queue_if_necessary( self, rqi,
> ready_queue );
> + _RBTree_Initialize_node( &node->Base.Base.Node.RBTree );
> + _RBTree_Prepend( &ready_queue->Queue, &node->Base.Base.Node.RBTree );
> }
>
> static inline void _Scheduler_EDF_SMP_Move_from_ready_to_scheduled(
> --
> 2.26.2
>
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