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.
86 lines
3.0 KiB
C
86 lines
3.0 KiB
C
/****************************************************************************
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* sched/sched/sched_idletask.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 <stdbool.h>
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#include <assert.h>
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#include <nuttx/init.h>
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#include <nuttx/sched.h>
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#include "sched/sched.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: sched_idletask
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*
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* Description:
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* Check if the caller is an IDLE thread. For most implementations of
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* the SYSLOG output semaphore locking is required for mutual exclusion.
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* The idle threads are unable to lock semaphores because they cannot
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* wait. So IDLE thread output is a special case and is treated much as
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* we treat debug output from an interrupt handler.
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*
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* Input Parameters:
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* None
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*
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* Returned Value:
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* true if the calling task is and IDLE thread.
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*
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****************************************************************************/
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bool sched_idletask(void)
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{
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FAR struct tcb_s *rtcb = this_task();
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/* If called early in the initialization sequence, the tasks lists may not
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* have been initialized and, in that case, rtcb may be NULL.
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*/
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DEBUGASSERT(rtcb != NULL || g_nx_initstate < OSINIT_TASKLISTS);
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if (rtcb != NULL)
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{
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/* The IDLE task TCB is distinguishable by a few things:
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*
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* (1) It always lies at the end of the task list,
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* (2) It always has priority zero, and
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* (3) It should have the TCB_FLAG_CPU_LOCKED flag set.
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*
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* In the non-SMP case, the IDLE task will also have PID=0, but that
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* is not a portable test because there are multiple IDLE tasks with
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* different PIDs in the SMP configuration.
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*/
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return is_idle_task(rtcb);
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}
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/* We must be on the IDLE thread if we are early in initialization */
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return true;
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}
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