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incubator-nuttx/sched/sched/sched_setpriority.c

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/****************************************************************************
* sched/sched/sched_setpriority.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdint.h>
#include <sched.h>
#include <assert.h>
#include <errno.h>
#include <nuttx/irq.h>
#include <nuttx/arch.h>
#include "irq/irq.h"
#include "sched/sched.h"
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: nxsched_nexttcb
*
* Description:
* Get the next highest priority ready-to-run task.
*
* Input Parameters:
* tcb - the TCB of task to reprioritize.
*
* Returned Value:
* TCB of the next highest priority ready-to-run task.
*
****************************************************************************/
#ifdef CONFIG_SMP
static FAR struct tcb_s *nxsched_nexttcb(FAR struct tcb_s *tcb)
{
FAR struct tcb_s *nxttcb = tcb->flink;
FAR struct tcb_s *rtrtcb;
/* Which task should run next? It will be either the next tcb in the
* assigned task list (nxttcb) or a TCB in the g_readytorun list. We can
* only select a task from that list if the affinity mask includes the
* tcb->cpu.
*
* If pre-emption is locked or another CPU is in a critical section,
* then use the 'nxttcb' which will probably be the IDLE thread.
*/
if (!nxsched_islocked_global() && !irq_cpu_locked(this_cpu()))
{
/* Search for the highest priority task that can run on tcb->cpu. */
for (rtrtcb = (FAR struct tcb_s *)list_readytorun()->head;
rtrtcb != NULL && !CPU_ISSET(tcb->cpu, &rtrtcb->affinity);
rtrtcb = rtrtcb->flink);
/* Return the TCB from the readyt-to-run list if it is the next
* highest priority task.
*/
if (rtrtcb != NULL &&
rtrtcb->sched_priority >= nxttcb->sched_priority)
{
return rtrtcb;
}
}
/* Otherwise, return the next TCB in the g_assignedtasks[] list...
* probably the TCB of the IDLE thread.
* REVISIT: What if it is not the IDLE thread?
*/
return nxttcb;
}
#endif
/****************************************************************************
* Name: nxsched_running_setpriority
*
* Description:
* This function sets the priority of a running task. This does nothing
* if we are increasing the priority of a running task. If we are dropping
* the priority of a running task, then this could cause then next lower
* priority task to run,
*
* 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.
*
* Input Parameters:
* tcb - the TCB of task to reprioritize.
* sched_priority - The new task priority
*
* Returned Value:
* None
*
****************************************************************************/
static inline void nxsched_running_setpriority(FAR struct tcb_s *tcb,
int sched_priority)
{
FAR struct tcb_s *nxttcb;
/* Get the TCB of the next highest priority, ready to run task */
#ifdef CONFIG_SMP
nxttcb = nxsched_nexttcb(tcb);
#else
nxttcb = tcb->flink;
#endif
DEBUGASSERT(nxttcb != NULL);
/* 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 <= nxttcb->sched_priority)
{
FAR struct tcb_s *rtcb = this_task();
if (rtcb->lockcount > 0)
{
/* Move all tasks with the higher priority from the ready-to-run
* list to the pending list.
*/
do
{
bool check = nxsched_remove_readytorun(nxttcb, false);
DEBUGASSERT(check == false);
UNUSED(check);
nxsched_add_prioritized(nxttcb, list_pendingtasks());
nxttcb->task_state = TSTATE_TASK_PENDING;
#ifdef CONFIG_SMP
nxttcb = nxsched_nexttcb(tcb);
#else
nxttcb = tcb->flink;
#endif
}
while (sched_priority < nxttcb->sched_priority);
/* Change the task priority */
tcb->sched_priority = (uint8_t)sched_priority;
}
else
{
/* A context switch will occur. */
if (nxsched_reprioritize_rtr(tcb, sched_priority))
{
up_switch_context(this_task(), rtcb);
}
}
}
/* Otherwise, we can just change priority since it has no effect */
else
{
/* Change the task priority */
tcb->sched_priority = (uint8_t)sched_priority;
}
}
/****************************************************************************
* Name: nxsched_readytorun_setpriority
*
* Description:
* This function sets the priority of a ready-to-run task. This may alter
* the position of the task in the ready-to-run list and if the priority
* is increased, may cause the task to become running.
*
* Input Parameters:
* tcb - the TCB of task to reprioritize.
* sched_priority - The new task priority
*
* Returned Value:
* None
*
****************************************************************************/
static void nxsched_readytorun_setpriority(FAR struct tcb_s *tcb,
int sched_priority)
{
FAR struct tcb_s *rtcb;
#ifdef CONFIG_SMP
int cpu;
/* CASE 2a. The task is ready-to-run (but not running) but not assigned to
* a CPU. An increase in priority could cause a context switch may be
* caused by the re-prioritization. The task is not assigned and may run
* on any CPU.
*/
if (tcb->task_state == TSTATE_TASK_READYTORUN)
{
cpu = nxsched_select_cpu(tcb->affinity);
}
/* CASE 2b. The task is ready to run, and assigned to a CPU. An increase
* in priority could cause this task to become running but the task can
* only run on its assigned CPU.
*/
else
{
cpu = tcb->cpu;
}
/* The running task is the task at the head of the g_assignedtasks[]
* associated with the selected CPU.
*/
rtcb = current_task(cpu);
#else
/* CASE 2. The task is ready-to-run (but not running) and a context switch
* may be caused by the re-prioritization.
*/
rtcb = this_task();
#endif
/* 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. */
if (nxsched_reprioritize_rtr(tcb, sched_priority))
{
up_switch_context(this_task(), rtcb);
}
}
/* 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 that it resides in.
* It should not be at the head of the list.
*/
bool check = nxsched_remove_readytorun(tcb, false);
DEBUGASSERT(check == false);
UNUSED(check);
/* Change the task priority */
tcb->sched_priority = (uint8_t)sched_priority;
/* Put it back into the correct ready-to-run task list. It must not
* end up at the head of the list.
*/
check = nxsched_add_readytorun(tcb);
DEBUGASSERT(check == false);
UNUSED(check);
}
}
/****************************************************************************
* Name: nxsched_blocked_setpriority
*
* Description:
* Change the priority of a blocked tasks. The only issue here is that
* the task may like in a prioritized or an non-prioritized queue.
*
* Input Parameters:
* tcb - the TCB of task to reprioritize.
* sched_priority - The new task priority
*
* Returned Value:
* None
*
****************************************************************************/
static inline void nxsched_blocked_setpriority(FAR struct tcb_s *tcb,
int sched_priority)
{
FAR dq_queue_t *tasklist;
tstate_t task_state = tcb->task_state;
/* CASE 3a. The task resides in a prioritized list. */
tasklist = TLIST_BLOCKED(tcb);
if (TLIST_ISPRIORITIZED(task_state))
{
/* Remove the TCB from the prioritized task list */
dq_rem((FAR dq_entry_t *)tcb, tasklist);
/* Change the task priority */
tcb->sched_priority = (uint8_t)sched_priority;
/* Put it back into the prioritized list at the correct position. */
nxsched_add_prioritized(tcb, tasklist);
}
/* CASE 3b. The task resides in a non-prioritized list. */
else
{
/* Just change the task's priority */
tcb->sched_priority = (uint8_t)sched_priority;
}
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: nxsched_set_priority
*
* 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.
*
* Input Parameters:
* tcb - the TCB of task to reprioritize.
* sched_priority - The new task priority
*
* Returned Value:
* On success, nxsched_set_priority() returns 0 (OK). On error, a negated
* errno value is returned.
*
* 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.
*
****************************************************************************/
int nxsched_set_priority(FAR struct tcb_s *tcb, int sched_priority)
{
irqstate_t flags;
/* Verify that the requested priority is in the valid range */
if (sched_priority < SCHED_PRIORITY_MIN ||
sched_priority > SCHED_PRIORITY_MAX)
{
return -EINVAL;
}
/* We need to assure that there there is no interrupt activity while
* performing the following.
*/
flags = enter_critical_section();
/* There are three major cases (and two sub-cases) that must be
* considered:
*/
switch (tcb->task_state)
{
/* CASE 1. The task is running and a context switch may be caused by
* the re-prioritization
*/
case TSTATE_TASK_RUNNING:
nxsched_running_setpriority(tcb, sched_priority);
break;
/* CASE 2. The task is ready-to-run (but not running) and a context
* switch may be caused by the re-prioritization
*/
case TSTATE_TASK_READYTORUN:
#ifdef CONFIG_SMP
case TSTATE_TASK_ASSIGNED:
#endif
nxsched_readytorun_setpriority(tcb, sched_priority);
break;
/* CASE 3. The task is not in the ready to run list. Changing its
* Priority cannot effect the currently executing task.
*/
default:
nxsched_blocked_setpriority(tcb, sched_priority);
break;
}
leave_critical_section(flags);
return OK;
}
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