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/****************************************************************************
* sched/sched/sched_setpriority.c
*
* Copyright (C) 2009, 2013 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 <sched.h>
#include <errno.h>
#include <nuttx/arch.h>
#include "sched/sched.h"
/****************************************************************************
* Definitions
****************************************************************************/
/****************************************************************************
* Private Type Declarations
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: sched_setpriority
*
* Description:
* This function sets the priority of a specified task.
*
* NOTE: Setting a task's priority to the same value has a similar effect
* to sched_yield() -- The task will be moved to after all other tasks
* with the same priority.
*
* Inputs:
* tcb - the TCB of task to reprioritize.
* sched_priority - The new task priority
*
* Return Value:
* On success, sched_setparam() returns 0 (OK). On error, -1 (ERROR) is
* returned, and errno is set appropriately.
*
* EINVAL The parameter 'param' is invalid or does not make sense for the
* current scheduling policy.
* EPERM The calling task does not have appropriate privileges.
* ESRCH The task whose ID is pid could not be found.
*
* Assumptions:
*
****************************************************************************/
int sched_setpriority(FAR struct tcb_s *tcb, int sched_priority)
{
FAR struct tcb_s *rtcb = (FAR struct tcb_s*)g_readytorun.head;
tstate_t task_state;
irqstate_t saved_state;
/* Verify that the requested priority is in the valid range */
if (sched_priority < SCHED_PRIORITY_MIN ||
sched_priority > SCHED_PRIORITY_MAX)
{
set_errno(EINVAL);
return ERROR;
}
/* We need to assure that there there is no interrupt activity while
* performing the following.
*/
saved_state = irqsave();
/* There are four cases that must be considered: */
task_state = tcb->task_state;
switch (task_state)
{
/* CASE 1. The task is running or ready-to-run and a context switch
* may be caused by the re-prioritization
*/
case TSTATE_TASK_RUNNING:
/* A context switch will occur if the new priority of the running
* task becomes less than OR EQUAL TO the next highest priority
* ready to run task.
*/
if (sched_priority <= tcb->flink->sched_priority)
{
/* A context switch will occur. */
up_reprioritize_rtr(tcb, (uint8_t)sched_priority);
}
/* Otherwise, we can just change priority since it has no effect */
else
{
/* Change the task priority */
tcb->sched_priority = (uint8_t)sched_priority;
}
break;
/* CASE 2. The task is running or ready-to-run and a context switch
* may be caused by the re-prioritization
*/
case TSTATE_TASK_READYTORUN:
/* A context switch will occur if the new priority of the ready-to
* run task is (strictly) greater than the current running task
*/
if (sched_priority > rtcb->sched_priority)
{
/* A context switch will occur. */
up_reprioritize_rtr(tcb, (uint8_t)sched_priority);
}
/* Otherwise, we can just change priority and re-schedule (since it
* have no other effect).
*/
else
{
/* Remove the TCB from the ready-to-run task list */
ASSERT(!sched_removereadytorun(tcb));
/* Change the task priority */
tcb->sched_priority = (uint8_t)sched_priority;
/* Put it back into the ready-to-run task list */
ASSERT(!sched_addreadytorun(tcb));
}
break;
/* CASE 3. The task is not in the ready to run list. Changing its
* Priority cannot effect the currently executing task.
*/
default:
/* CASE 3a. The task resides in a prioritized list. */
if (g_tasklisttable[task_state].prioritized)
{
/* Remove the TCB from the prioritized task list */
dq_rem((FAR dq_entry_t*)tcb, (FAR dq_queue_t*)g_tasklisttable[task_state].list);
/* Change the task priority */
tcb->sched_priority = (uint8_t)sched_priority;
/* Put it back into the prioritized list at the correct
* position
*/
sched_addprioritized(tcb, (FAR dq_queue_t*)g_tasklisttable[task_state].list);
}
/* CASE 3b. The task resides in a non-prioritized list. */
else
{
/* Just change the task's priority */
tcb->sched_priority = (uint8_t)sched_priority;
}
break;
}
irqrestore(saved_state);
return OK;
}
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