diff options
Diffstat (limited to 'nuttx/sched/sched_setpriority.c')
| -rw-r--r-- | nuttx/sched/sched_setpriority.c | 230 |
1 files changed, 230 insertions, 0 deletions
diff --git a/nuttx/sched/sched_setpriority.c b/nuttx/sched/sched_setpriority.c new file mode 100644 index 000000000..a071a7259 --- /dev/null +++ b/nuttx/sched/sched_setpriority.c @@ -0,0 +1,230 @@ +/**************************************************************************** + * 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 <sys/types.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, (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, (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); + return OK; +} |