/************************************************************ * sched_setparam.c * * Copyright (C) 2007 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * 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 #include #include #include #include #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. */ up_reprioritize_rtr(tcb, (ubyte)sched_priority); } /* 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. */ up_reprioritize_rtr(tcb, (ubyte)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 = (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, 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, 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; }