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233 lines
7.6 KiB
233 lines
7.6 KiB
/**************************************************************************** |
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* sched/sched_setpriority.c |
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* |
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* Copyright (C) 2009 Gregory Nutt. All rights reserved. |
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* Author: Gregory Nutt <gnutt@nuttx.org> |
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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 <stdint.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_setpriority |
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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 effect |
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* to sched_yield() -- The task will be moved to after all other tasks |
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* 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 (ERROR) is |
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* returned, and errno is set appropriately. |
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* |
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* EINVAL The parameter 'param' is invalid or does not make sense for the |
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* 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_setpriority(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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/* Verify that the requested priority is in the valid range */ |
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if (sched_priority < SCHED_PRIORITY_MIN || |
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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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/* 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, (uint8_t)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 = (uint8_t)sched_priority; |
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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, (uint8_t)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 = (uint8_t)sched_priority; |
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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 = (uint8_t)sched_priority; |
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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 = (uint8_t)sched_priority; |
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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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