286 lines
8.9 KiB
C
286 lines
8.9 KiB
C
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/****************************************************************************
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* sched/sched_settcbprio.c
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*
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* Copyright (C) 2009 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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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 <sys/types.h>
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#include <sched.h>
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#include <errno.h>
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#include <nuttx/arch.h>
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#include "os_internal.h"
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/****************************************************************************
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* Definitions
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****************************************************************************/
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/****************************************************************************
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* Private Type Declarations
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****************************************************************************/
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/****************************************************************************
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* Global Variables
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****************************************************************************/
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/****************************************************************************
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* Private Variables
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****************************************************************************/
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: sched_settcbprio
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*
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* Description:
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* This function sets the priority of a specified task.
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*
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* NOTE: Setting a task's priority to the same value has a similar
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* effect to sched_yield() -- The task will be moved to after all other
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* tasks with the same priority.
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*
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* Inputs:
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* tcb - the TCB of task to reprioritize.
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* sched_priority - The new task priority
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*
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* Return Value:
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* On success, sched_setparam() returns 0 (OK). On error, -1
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* (ERROR) is returned, and errno is set appropriately.
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*
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* EINVAL The parameter 'param' is invalid or does not make
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* sense for the current scheduling policy.
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* EPERM The calling task does not have appropriate privileges.
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* ESRCH The task whose ID is pid could not be found.
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*
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* Assumptions:
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*
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****************************************************************************/
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int sched_settcbprio(FAR _TCB *tcb, int sched_priority)
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{
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FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
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tstate_t task_state;
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irqstate_t saved_state;
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/* We need to assure that there there is no interrupt activity while
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* performing the following.
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*/
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saved_state = irqsave();
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/* There are four cases that must be considered: */
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task_state = tcb->task_state;
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switch (task_state)
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{
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/* CASE 1. The task is running or ready-to-run and a context switch
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* may be caused by the re-prioritization
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*/
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case TSTATE_TASK_RUNNING:
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/* A context switch will occur if the new priority of the running
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* task becomes less than OR EQUAL TO the next highest priority
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* ready to run task.
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*/
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if (sched_priority <= tcb->flink->sched_priority)
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{
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/* A context switch will occur. */
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up_reprioritize_rtr(tcb, (ubyte)sched_priority);
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}
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/* Otherwise, we can just change priority since it has no effect */
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else
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{
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/* Change the task priority */
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tcb->sched_priority = (ubyte)sched_priority;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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tcb->base_priority = (ubyte)sched_priority;
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#endif
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}
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break;
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/* CASE 2. The task is running or ready-to-run and a context switch
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* may be caused by the re-prioritization
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*/
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case TSTATE_TASK_READYTORUN:
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/* A context switch will occur if the new priority of the ready-to
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* run task is (strictly) greater than the current running task
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*/
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if (sched_priority > rtcb->sched_priority)
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{
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/* A context switch will occur. */
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up_reprioritize_rtr(tcb, (ubyte)sched_priority);
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}
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/* Otherwise, we can just change priority and re-schedule (since it
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* have no other effect).
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*/
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else
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{
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/* Remove the TCB from the ready-to-run task list */
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ASSERT(!sched_removereadytorun(tcb));
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/* Change the task priority */
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tcb->sched_priority = (ubyte)sched_priority;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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tcb->base_priority = (ubyte)sched_priority;
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#endif
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/* Put it back into the ready-to-run task list */
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ASSERT(!sched_addreadytorun(tcb));
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}
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break;
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/* CASE 3. The task is not in the ready to run list. Changing its
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* Priority cannot effect the currently executing task.
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*/
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default:
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/* CASE 3a. The task resides in a prioritized list. */
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if (g_tasklisttable[task_state].prioritized)
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{
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/* Remove the TCB from the prioritized task list */
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dq_rem((FAR dq_entry_t*)tcb, (FAR dq_queue_t*)g_tasklisttable[task_state].list);
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/* Change the task priority */
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tcb->sched_priority = (ubyte)sched_priority;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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tcb->base_priority = (ubyte)sched_priority;
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#endif
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/* Put it back into the prioritized list at the correct
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* position
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*/
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sched_addprioritized(tcb, (FAR dq_queue_t*)g_tasklisttable[task_state].list);
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}
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/* CASE 3b. The task resides in a non-prioritized list. */
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else
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{
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/* Just change the task's priority */
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tcb->sched_priority = (ubyte)sched_priority;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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tcb->base_priority = (ubyte)sched_priority;
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#endif
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}
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break;
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}
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irqrestore(saved_state);
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return OK;
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}
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int sched_setparam(pid_t pid, const struct sched_param *param)
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{
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FAR _TCB *rtcb;
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FAR _TCB *tcb;
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int ret;
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/* Verify that the requested priority is in the valid range */
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if (!param ||
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param->sched_priority < SCHED_PRIORITY_MIN ||
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param->sched_priority > SCHED_PRIORITY_MAX)
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{
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errno = EINVAL;
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return ERROR;
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}
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/* Prohibit modifications to the head of the ready-to-run task
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* list while adjusting the priority
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*/
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sched_lock();
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/* Check if the task to reprioritize is the calling task */
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rtcb = (FAR _TCB*)g_readytorun.head;
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if (pid == 0 || pid == rtcb->pid)
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{
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tcb = rtcb;
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}
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/* The pid is not the calling task, we will have to search for it */
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else
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{
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tcb = sched_gettcb(pid);
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if (!tcb)
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{
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/* No task with this pid was found */
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errno = ESRCH;
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sched_unlock();
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return ERROR;
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}
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}
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/* Then perform the reprioritization */
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ret = sched_settcbprio(tcb, param->sched_priority);
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sched_unlock();
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return ret;
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}
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