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incubator-nuttx/sched/sched_setparam.c

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/************************************************************
* sched_setparam.c
*
* Copyright (C) 2007 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* 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 Gregory Nutt 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 <sys/types.h>
#include <sched.h>
#include <nuttx/arch.h>
#include <nuttx/os_external.h>
#include "os_internal.h"
/************************************************************
* Definitions
************************************************************/
/************************************************************
* Private Type Declarations
************************************************************/
/************************************************************
* Global Variables
************************************************************/
/************************************************************
* Private Variables
************************************************************/
/************************************************************
* Private Function Prototypes
************************************************************/
/************************************************************
* Private Functions
************************************************************/
/************************************************************
* Public Functions
************************************************************/
/************************************************************
* Name: sched_setparam
*
* Description:
* This function sets the priority of a specified task.
*
* NOTE: Setting a task's priority to the same value has the
* similar effect to sched_yield() -- The task will be moved to
* after all other tasks with the same priority.
*
* Inputs:
* pid - the task ID of the task to reprioritize. If pid is
* zero, the priority of the calling task is changed.
* param - A structure whose member sched_priority is the integer
* priority. The range of valid priority numbers is from
* SCHED_PRIORITY_MIN through SCHED_PRIORITY_MAX.
*
* Return Value:
* OK if successful, otherwise ERROR. This function can
* fail for the following reasons:
*
* (1) parm is NULL or parm->sched_priority is out of
* range.
* (2) pid does not correspond to any task.
*
* (errno is not set).
*
* Assumptions:
*
************************************************************/
int sched_setparam(pid_t pid, const struct sched_param *param)
{
FAR _TCB *rtcb;
FAR _TCB *tcb;
tstate_t task_state;
irqstate_t saved_state;
int sched_priority = param->sched_priority;
int ret = 0;
/* Verify that the requested priority is in the valid range */
if (!param ||
param->sched_priority < SCHED_PRIORITY_MIN ||
param->sched_priority > SCHED_PRIORITY_MAX)
{
return ERROR;
}
/* Prohibit modifications to the head of the ready-to-run task
* list while adjusting the priority
*/
sched_lock();
/* Check if the task to reprioritize is the calling task */
rtcb = (FAR _TCB*)g_readytorun.head;
if (pid == 0 || pid == rtcb->pid)
{
tcb = rtcb;
}
/* The pid is not the calling task, we will have to search for it */
else
{
tcb = sched_gettcb(pid);
if (!tcb)
{
/* No task with this pid was found */
sched_unlock();
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. */
irqstate_t flags = irqsave();
up_reprioritize_rtr(tcb, (ubyte)sched_priority);
irqrestore(flags);
}
/* Otherwise, we can just change priority since it has no effect */
else
{
/* Change the task priority */
tcb->sched_priority = (ubyte)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. */
irqstate_t flags = irqsave();
up_reprioritize_rtr(tcb, (ubyte)sched_priority);
irqrestore(flags);
}
/* 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 = (ubyte)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 = (ubyte)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 = (ubyte)sched_priority;
}
break;
}
irqrestore(saved_state);
sched_unlock();
return ret;
}
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