142 lines
4.3 KiB
C
142 lines
4.3 KiB
C
/****************************************************************************
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* sched/sched/sched_addprioritized.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 <stdint.h>
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#include <stdbool.h>
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#include <assert.h>
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#include <nuttx/queue.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: nxsched_add_prioritized
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*
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* Description:
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* This function adds a TCB to a prioritized TCB list.
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*
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* Input Parameters:
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* tcb - Points to the TCB to add to the prioritized list
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* list - Points to the prioritized list to add tcb to
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*
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* Returned Value:
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* true if the head of the list has changed.
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*
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* Assumptions:
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* - The caller has established a critical section before
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* calling this function (calling sched_lock() first is NOT
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* a good idea -- use enter_critical_section()).
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* - The caller has already removed the input tcb from
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* whatever list it was in.
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* - The caller handles the condition that occurs if the
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* the head of the task list is changed.
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* - The caller must set the task_state field of the TCB to
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* match the state associated with the list.
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*
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****************************************************************************/
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bool nxsched_add_prioritized(FAR struct tcb_s *tcb, DSEG dq_queue_t *list)
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{
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FAR struct tcb_s *next;
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FAR struct tcb_s *prev;
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uint8_t sched_priority = tcb->sched_priority;
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bool ret = false;
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/* Lets do a sanity check before we get started. */
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DEBUGASSERT(sched_priority >= SCHED_PRIORITY_MIN);
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/* Search the list to find the location to insert the new Tcb.
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* Each is list is maintained in descending sched_priority order.
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*/
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for (next = (FAR struct tcb_s *)list->head;
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(next && sched_priority <= next->sched_priority);
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next = next->flink);
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/* Add the tcb to the spot found in the list. Check if the tcb
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* goes at the end of the list. NOTE: This could only happen if list
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* is the g_pendingtasks list!
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*/
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if (next == NULL)
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{
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/* The tcb goes at the end of the list. */
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prev = (FAR struct tcb_s *)list->tail;
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if (prev == NULL)
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{
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/* Special case: The list is empty */
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tcb->flink = NULL;
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tcb->blink = NULL;
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list->head = (FAR dq_entry_t *)tcb;
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list->tail = (FAR dq_entry_t *)tcb;
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ret = true;
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}
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else
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{
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/* The tcb goes at the end of a non-empty list */
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tcb->flink = NULL;
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tcb->blink = prev;
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prev->flink = tcb;
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list->tail = (FAR dq_entry_t *)tcb;
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}
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}
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else
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{
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/* The tcb goes just before next */
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prev = next->blink;
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if (prev == NULL)
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{
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/* Special case: Insert at the head of the list */
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tcb->flink = next;
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tcb->blink = NULL;
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next->blink = tcb;
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list->head = (FAR dq_entry_t *)tcb;
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ret = true;
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}
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else
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{
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/* Insert in the middle of the list */
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tcb->flink = next;
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tcb->blink = prev;
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prev->flink = tcb;
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next->blink = tcb;
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}
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}
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return ret;
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}
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