/************************************************************************
* sched/sched_addprioritized.c
*
* Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
************************************************************************/
/************************************************************************
* Included Files
************************************************************************/
#include <nuttx/config.h>
#include <stdint.h>
#include <stdbool.h>
#include <queue.h>
#include <assert.h>
#include "os_internal.h"
/************************************************************************
* Pre-processor Definitions
************************************************************************/
/************************************************************************
* Private Type Declarations
************************************************************************/
/************************************************************************
* Global Variables
************************************************************************/
/************************************************************************
* Private Variables
************************************************************************/
/************************************************************************
* Private Function Prototypes
************************************************************************/
/************************************************************************
* Public Functions
************************************************************************/
/************************************************************************
* Name: sched_addprioritized
*
* Description:
* This function adds a TCB to a prioritized TCB list.
*
* Inputs:
* tcb - Points to the TCB to add to the prioritized list
* list - Points to the prioritized list to add tcb to
*
* Return Value:
* true if the head of the list has changed.
*
* Assumptions:
* - The caller has established a critical section before
* calling this function (calling sched_lock() first is NOT
* a good idea -- use irqsave()).
* - The caller has already removed the input tcb from
* whatever list it was in.
* - The caller handles the condition that occurs if the
* the head of the task list is changed.
* - The caller must set the task_state field of the TCB to
* match the state associated with the list.
************************************************************************/
bool sched_addprioritized(FAR _TCB *tcb, DSEG dq_queue_t *list)
{
FAR _TCB *next;
FAR _TCB *prev;
uint8_t sched_priority = tcb->sched_priority;
bool ret = false;
/* Lets do a sanity check before we get started. */
ASSERT(sched_priority >= SCHED_PRIORITY_MIN);
/* Search the list to find the location to insert the new Tcb.
* Each is list is maintained in ascending sched_priority order.
*/
for (next = (FAR _TCB*)list->head;
(next && sched_priority <= next->sched_priority);
next = next->flink);
/* Add the tcb to the spot found in the list. Check if the tcb
* goes at the end of the list. NOTE: This could only happen if list
* is the g_pendingtasks list!
*/
if (!next)
{
/* The tcb goes at the end of the list. */
prev = (FAR _TCB*)list->tail;
if (!prev)
{
/* Special case: The list is empty */
tcb->flink = NULL;
tcb->blink = NULL;
list->head = (FAR dq_entry_t*)tcb;
list->tail = (FAR dq_entry_t*)tcb;
ret = true;
}
else
{
/* The tcb goes at the end of a non-empty list */
tcb->flink = NULL;
tcb->blink = prev;
prev->flink = tcb;
list->tail = (FAR dq_entry_t*)tcb;
}
}
else
{
/* The tcb goes just before next */
prev = (FAR _TCB*)next->blink;
if (!prev)
{
/* Special case: Insert at the head of the list */
tcb->flink = next;
tcb->blink = NULL;
next->blink = tcb;
list->head = (FAR dq_entry_t*)tcb;
ret = true;
}
else
{
/* Insert in the middle of the list */
tcb->flink = next;
tcb->blink = prev;
prev->flink = tcb;
next->blink = tcb;
}
}
return ret;
}
