394 lines
13 KiB
C
394 lines
13 KiB
C
/****************************************************************************
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* sched/work/work_inherit.c
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*
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* Copyright (C) 2014, 2016 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 <sched.h>
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#include <nuttx/irq.h>
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#include <nuttx/wqueue.h>
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#include "sched/sched.h"
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#include "wqueue/wqueue.h"
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#if defined(CONFIG_SCHED_WORKQUEUE) && defined(CONFIG_SCHED_LPWORK) && \
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defined(CONFIG_PRIORITY_INHERITANCE)
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: lpwork_boostworker
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*
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* Description:
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* Called by the work queue client to assure that the priority of the low-
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* priority worker thread is at least at the requested level, reqprio. This
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* function would normally be called just before calling work_queue().
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*
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* Parameters:
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* reqprio - Requested minimum worker thread priority
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*
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* Return Value:
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* None
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*
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****************************************************************************/
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static void lpwork_boostworker(pid_t wpid, uint8_t reqprio)
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{
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FAR struct tcb_s *wtcb;
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/* Get the TCB of the low priority worker thread from the process ID. */
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wtcb = sched_gettcb(wpid);
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DEBUGASSERT(wtcb);
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#if CONFIG_SEM_NNESTPRIO > 0
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/* If the priority of the client thread that is greater than the base
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* priority of the worker thread, then we may need to adjust the worker
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* thread's priority now or later to that priority.
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*/
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if (reqprio > wtcb->base_priority)
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{
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/* If the new priority is greater than the current, possibly already
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* boosted priority of the worker thread, then we will have to raise
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* the worker thread's priority now.
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*/
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if (reqprio > wtcb->sched_priority)
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{
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/* If the current priority of worker thread has already been
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* boosted, then add the boost priority to the list of restoration
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* priorities. When the higher priority waiter thread gets its
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* count, then we need to revert the worker thread to this saved
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* priority (not to its base priority).
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*/
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if (wtcb->sched_priority > wtcb->base_priority)
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{
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/* Save the current, boosted priority of the worker thread. */
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if (wtcb->npend_reprio < CONFIG_SEM_NNESTPRIO)
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{
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wtcb->pend_reprios[wtcb->npend_reprio] = wtcb->sched_priority;
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wtcb->npend_reprio++;
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}
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}
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/* Raise the priority of the worker. This cannot cause a context
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* switch because we have preemption disabled. The worker thread
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* may be marked "pending" and the switch may occur during
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* sched_unblock() processing.
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*/
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(void)sched_setpriority(wtcb, reqprio);
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}
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else
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{
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/* The new priority is above the base priority of the worker,
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* but not as high as its current working priority. Just put it
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* in the list of pending restoration priorities so that when the
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* higher priority thread gets its count, we can revert to this
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* saved priority and not to the base priority.
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*/
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wtcb->pend_reprios[wtcb->npend_reprio] = reqprio;
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wtcb->npend_reprio++;
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}
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}
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#else
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/* If the priority of the client thread that is less than of equal to the
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* priority of the worker thread, then do nothing because the thread is
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* already running at a sufficient priority.
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*/
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if (reqprio > wtcb->sched_priority)
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{
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/* Raise the priority of the worker thread. This cannot cause
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* context switch because we have preemption disabled. The task
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* will be marked "pending" and the switch will occur during
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* sched_unlock() processing.
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*/
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(void)sched_setpriority(wtcb, reqprio);
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}
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#endif
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}
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/****************************************************************************
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* Name: lpwork_restoreworker
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*
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* Description:
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* This function is called to restore the priority after it was previously
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* boosted. This is often done by client logic on the worker thread when
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* the scheduled work completes. It will check if we need to drop the
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* priority of the worker thread.
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*
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* Parameters:
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* reqprio - Previously requested minimum worker thread priority to be
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* "unboosted"
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*
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* Return Value:
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* None
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*
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****************************************************************************/
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static void lpwork_restoreworker(pid_t wpid, uint8_t reqprio)
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{
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FAR struct tcb_s *wtcb;
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#if CONFIG_SEM_NNESTPRIO > 0
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uint8_t wpriority;
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int index;
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int selected;
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#endif
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/* Get the TCB of the low priority worker thread from the process ID. */
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wtcb = sched_gettcb(wpid);
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DEBUGASSERT(wtcb);
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/* Was the priority of the worker thread boosted? If so, then drop its
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* priority back to the correct level. What is the correct level?
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*/
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if (wtcb->sched_priority != wtcb->base_priority)
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{
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#if CONFIG_SEM_NNESTPRIO > 0
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/* Are there other, pending priority levels to revert to? */
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if (wtcb->npend_reprio < 1)
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{
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/* No... the worker thread has only been boosted once.
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* npend_reprio should be 0 and the boosted priority should be the
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* priority of the client task (reqprio)
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*
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* That latter assumption may not be true if the client's priority
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* was also boosted so that it no longer matches the wtcb's
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* sched_priority. Or if CONFIG_SEM_NNESTPRIO is too small (so
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* that we do not have a proper record of the reprioritizations).
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*/
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DEBUGASSERT(/* wtcb->sched_priority == reqprio && */
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wtcb->npend_reprio == 0);
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/* Reset the worker's priority back to the base priority. */
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sched_reprioritize(wtcb, wtcb->base_priority);
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}
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/* There are multiple pending priority levels. The worker thread's
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* "boosted" priority could greater than or equal to "reqprio" (it could
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* be greater if its priority we boosted because it also holds some
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* semaphore).
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*/
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else if (wtcb->sched_priority <= reqprio)
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{
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/* The worker thread has been boosted to the same priority as the
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* waiter thread that just received the count. We will simply
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* reprioritize to the next highest pending priority.
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*/
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/* Find the highest pending priority and remove it from the list */
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for (index = 1, selected = 0; index < wtcb->npend_reprio; index++)
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{
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if (wtcb->pend_reprios[index] > wtcb->pend_reprios[selected])
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{
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selected = index;
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}
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}
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/* Remove the highest priority pending priority from the list */
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wpriority = wtcb->pend_reprios[selected];
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index = wtcb->npend_reprio - 1;
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if (index > 0)
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{
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wtcb->pend_reprios[selected] = wtcb->pend_reprios[index];
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}
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wtcb->npend_reprio = index;
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/* And apply that priority to the thread (while retaining the
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* base_priority)
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*/
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sched_setpriority(wtcb, wpriority);
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}
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else
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{
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/* The worker thread has been boosted to a higher priority than the
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* waiter task. The pending priority should be in the list (unless
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* it was lost because of of list overflow or because the worker
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* was reprioritized again unbeknownst to the priority inheritance
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* logic).
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*
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* Search the list for the matching priority.
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*/
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for (index = 0; index < wtcb->npend_reprio; index++)
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{
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/* Does this pending priority match the priority of the thread
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* that just received the count?
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*/
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if (wtcb->pend_reprios[index] == reqprio)
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{
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/* Yes, remove it from the list */
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selected = wtcb->npend_reprio - 1;
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if (selected > 0)
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{
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wtcb->pend_reprios[index] = wtcb->pend_reprios[selected];
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}
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wtcb->npend_reprio = selected;
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break;
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}
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}
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}
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#else
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/* There is no alternative restore priorities, drop the priority
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* of the worker thread all the way back to the threads "base"
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* priority.
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*/
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sched_reprioritize(wtcb, wtcb->base_priority);
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#endif
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}
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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: lpwork_boostpriority
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*
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* Description:
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* Called by the work queue client to assure that the priority of the low-
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* priority worker thread is at least at the requested level, reqprio. This
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* function would normally be called just before calling work_queue().
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*
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* Parameters:
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* reqprio - Requested minimum worker thread priority
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*
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* Return Value:
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* None
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*
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****************************************************************************/
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void lpwork_boostpriority(uint8_t reqprio)
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{
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irqstate_t flags;
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int wndx;
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/* Clip to the configured maximum priority */
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if (reqprio > CONFIG_SCHED_LPWORKPRIOMAX)
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{
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reqprio = CONFIG_SCHED_LPWORKPRIOMAX;
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}
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/* Prevent context switches until we get the priorities right */
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flags = enter_critical_section();
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sched_lock();
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/* Adjust the priority of every worker thread */
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for (wndx = 0; wndx < CONFIG_SCHED_LPNTHREADS; wndx++)
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{
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lpwork_boostworker(g_lpwork.worker[wndx].pid, reqprio);
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}
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sched_unlock();
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leave_critical_section(flags);
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}
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/****************************************************************************
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* Name: lpwork_restorepriority
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*
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* Description:
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* This function is called to restore the priority after it was previously
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* boosted. This is often done by client logic on the worker thread when
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* the scheduled work completes. It will check if we need to drop the
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* priority of the worker thread.
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*
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* Parameters:
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* reqprio - Previously requested minimum worker thread priority to be
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* "unboosted"
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*
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* Return Value:
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* None
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*
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****************************************************************************/
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void lpwork_restorepriority(uint8_t reqprio)
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{
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irqstate_t flags;
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int wndx;
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/* Clip to the configured maximum priority */
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if (reqprio > CONFIG_SCHED_LPWORKPRIOMAX)
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{
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reqprio = CONFIG_SCHED_LPWORKPRIOMAX;
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}
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/* Prevent context switches until we get the priorities right */
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flags = enter_critical_section();
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sched_lock();
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/* Adjust the priority of every worker thread */
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for (wndx = 0; wndx < CONFIG_SCHED_LPNTHREADS; wndx++)
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{
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lpwork_restoreworker(g_lpwork.worker[wndx].pid, reqprio);
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}
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sched_unlock();
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leave_critical_section(flags);
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}
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#endif /* CONFIG_SCHED_WORKQUEUE && CONFIG_SCHED_LPWORK && CONFIG_PRIORITY_INHERITANCE */
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