18266c1012
Pid is more appropriate than the flink pointer to determine idle task, when we want to use other data structure to optimize the task list.
109 lines
3.3 KiB
C
109 lines
3.3 KiB
C
/****************************************************************************
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* sched/sched/sched_cpuselect.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <sys/types.h>
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#include <assert.h>
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#include <nuttx/sched.h>
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#include "sched/sched.h"
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#ifdef CONFIG_SMP
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define IMPOSSIBLE_CPU 0xff
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: nxsched_select_cpu
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*
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* Description:
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* Return the index to the CPU with the lowest priority running task,
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* possibly its IDLE task.
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*
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* Input Parameters:
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* affinity - The set of CPUs on which the thread is permitted to run.
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*
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* Returned Value:
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* Index of the CPU with the lowest priority running task
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*
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* Assumptions:
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* Called from within a critical section.
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*
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****************************************************************************/
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int nxsched_select_cpu(cpu_set_t affinity)
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{
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uint8_t minprio;
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int cpu;
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int i;
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minprio = SCHED_PRIORITY_MAX;
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cpu = IMPOSSIBLE_CPU;
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for (i = 0; i < CONFIG_SMP_NCPUS; i++)
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{
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/* Is the thread permitted to run on this CPU? */
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if ((affinity & (1 << i)) != 0)
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{
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FAR struct tcb_s *rtcb = (FAR struct tcb_s *)
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g_assignedtasks[i].head;
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/* If this CPU is executing its IDLE task, then use it. The
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* IDLE task is always the last task in the assigned task list.
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*/
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if (is_idle_task(rtcb))
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{
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/* The IDLE task should always be assigned to this CPU and have
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* a priority of zero.
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*/
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DEBUGASSERT(rtcb->sched_priority == 0);
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return i;
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}
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else if (rtcb->sched_priority <= minprio)
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{
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DEBUGASSERT(rtcb->sched_priority > 0);
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minprio = rtcb->sched_priority;
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cpu = i;
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}
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}
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}
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DEBUGASSERT(cpu != IMPOSSIBLE_CPU);
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return cpu;
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}
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#endif /* CONFIG_SMP */
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