| /**************************************************************************** |
| * sched/sched_setpriority.c |
| * |
| * Copyright (C) 2009 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 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 "os_internal.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 _TCB *tcb, int sched_priority) |
| { |
| FAR _TCB *rtcb = (FAR _TCB*)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) |
| { |
| 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; |
| } |
