/****************************************************************************
* arch/arm/src/common/up_reprioritizertr.c
*
* Copyright (C) 2007-2009 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 <debug.h>
#include <nuttx/arch.h>
#include "os_internal.h"
#include "up_internal.h"
/****************************************************************************
* Private Definitions
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: up_reprioritize_rtr
*
* Description:
* Called when the priority of a running or
* ready-to-run task changes and the reprioritization will
* cause a context switch. Two cases:
*
* 1) The priority of the currently running task drops and the next
* task in the ready to run list has priority.
* 2) An idle, ready to run task's priority has been raised above the
* the priority of the current, running task and it now has the
* priority.
*
* Inputs:
* tcb: The TCB of the task that has been reprioritized
* priority: The new task priority
*
****************************************************************************/
void up_reprioritize_rtr(_TCB *tcb, ubyte priority)
{
/* Verify that the caller is sane */
if (tcb->task_state < FIRST_READY_TO_RUN_STATE ||
tcb->task_state > LAST_READY_TO_RUN_STATE ||
priority < SCHED_PRIORITY_MIN ||
priority > SCHED_PRIORITY_MAX)
{
PANIC(OSERR_BADREPRIORITIZESTATE);
}
else
{
_TCB *rtcb = (_TCB*)g_readytorun.head;
boolean switch_needed;
slldbg("TCB=%p PRI=%d\n", tcb, priority);
/* Remove the tcb task from the ready-to-run list.
* sched_removereadytorun will return TRUE if we just
* remove the head of the ready to run list.
*/
switch_needed = sched_removereadytorun(tcb);
/* Setup up the new task priority */
tcb->sched_priority = (ubyte)priority;
/* Return the task to the specified blocked task list.
* sched_addreadytorun will return TRUE if the task was
* added to the new list. We will need to perform a context
* switch only if the EXCLUSIVE or of the two calls is non-zero
* (i.e., one and only one the calls changes the head of the
* ready-to-run list).
*/
switch_needed ^= sched_addreadytorun(tcb);
/* Now, perform the context switch if one is needed */
if (switch_needed)
{
/* If we are going to do a context switch, then now is the right
* time to add any pending tasks back into the ready-to-run list.
* task list now
*/
if (g_pendingtasks.head)
{
sched_mergepending();
}
/* Are we in an interrupt handler? */
if (current_regs)
{
/* Yes, then we have to do things differently.
* Just copy the current_regs into the OLD rtcb.
*/
up_copystate(rtcb->xcp.regs, current_regs);
/* Restore the exception context of the rtcb at the (new) head
* of the g_readytorun task list.
*/
rtcb = (_TCB*)g_readytorun.head;
slldbg("New Active Task TCB=%p\n", rtcb);
/* Then switch contexts */
up_copystate(current_regs, rtcb->xcp.regs);
}
/* Copy the exception context into the TCB at the (old) head of the
* g_readytorun Task list. if up_saveusercontext returns a non-zero
* value, then this is really the previously running task restarting!
*/
else if (!up_saveusercontext(rtcb->xcp.regs))
{
/* Restore the exception context of the rtcb at the (new) head
* of the g_readytorun task list.
*/
rtcb = (_TCB*)g_readytorun.head;
slldbg("New Active Task TCB=%p\n", rtcb);
/* Then switch contexts */
up_fullcontextrestore(rtcb->xcp.regs);
}
}
}
}
