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/****************************************************************************
* sched/sched_addreadytorun.c
*
* Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 <stdbool.h>
#include <queue.h>
#include <assert.h>
#include "os_internal.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Type Declarations
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: sched_addreadytorun
*
* Description:
* This function adds a TCB to the ready to run
* list. If the currently active task has preemption disabled
* and the new TCB would cause this task to be preempted, the
* new task is added to the g_pendingtasks list instead. The
* pending tasks will be made ready-to-run when preemption
* is unlocked.
*
* Inputs:
* btcb - Points to the blocked TCB that is ready-to-run
*
* Return Value:
* true if the currently active task (the head of the
* g_readytorun list) has changed.
*
* Assumptions:
* - The caller has established a critical section before
* calling this function (calling sched_lock() first is NOT
* a good idea -- use irqsave()).
* - The caller has already removed the input rtcb from
* whatever list it was in.
* - The caller handles the condition that occurs if the
* the head of the g_readytorun list is changed.
*
****************************************************************************/
bool sched_addreadytorun(FAR _TCB *btcb)
{
FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
bool ret;
/* Check if pre-emption is disabled for the current running task and if
* the new ready-to-run task would cause the current running task to be
* preempted.
*/
if (rtcb->lockcount && rtcb->sched_priority < btcb->sched_priority)
{
/* Yes. Preemption would occur! Add the new ready-to-run task to the
* g_pendingtasks task list for now.
*/
sched_addprioritized(btcb, (FAR dq_queue_t*)&g_pendingtasks);
btcb->task_state = TSTATE_TASK_PENDING;
ret = false;
}
/* Otherwise, add the new task to the g_readytorun task list */
else if (sched_addprioritized(btcb, (FAR dq_queue_t*)&g_readytorun))
{
/* Information the instrumentation logic that we are switching tasks */
sched_note_switch(rtcb, btcb);
/* The new btcb was added at the head of the g_readytorun list. It
* is now to new active task!
*/
ASSERT(!rtcb->lockcount && btcb->flink != NULL);
btcb->task_state = TSTATE_TASK_RUNNING;
btcb->flink->task_state = TSTATE_TASK_READYTORUN;
ret = true;
}
else
{
/* The new btcb was added in the middle of the g_readytorun list */
btcb->task_state = TSTATE_TASK_READYTORUN;
ret = false;
}
return ret;
}
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