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/************************************************************************
* sched/sched_unlock.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 <nuttx/arch.h>
#include "os_internal.h"
/************************************************************************
* Definitions
************************************************************************/
/************************************************************************
* Private Type Declarations
************************************************************************/
/************************************************************************
* Global Variables
************************************************************************/
/************************************************************************
* Private Variables
************************************************************************/
/************************************************************************
* Private Function Prototypes
************************************************************************/
/************************************************************************
* Private Functionss
************************************************************************/
/************************************************************************
* Public Functions
************************************************************************/
/************************************************************************
* Name: sched_unlock
*
* Description:
* This function decrements the preemption lock count. Typically this
* is paired with sched_lock() and concludes a critical section of
* code. Preemption will not be unlocked until sched_unlock() has
* been called as many times as sched_lock(). When the lockcount is
* decremented to zero, any tasks that were eligible to preempt the
* current task will execute.
*
************************************************************************/
int sched_unlock(void)
{
struct tcb_s *rtcb = (struct tcb_s*)g_readytorun.head;
/* Check for some special cases: (1) rtcb may be NULL only during
* early boot-up phases, and (2) sched_unlock() should have no
* effect if called from the interrupt level.
*/
if (rtcb && !up_interrupt_context())
{
/* Prevent context switches throughout the following */
irqstate_t flags = irqsave();
/* Decrement the preemption lock counter */
if (rtcb->lockcount)
{
rtcb->lockcount--;
}
/* Check if the lock counter has decremented to zero. If so,
* then pre-emption has been re-enabled.
*/
if (rtcb->lockcount <= 0)
{
rtcb->lockcount = 0;
/* Release any ready-to-run tasks that have collected in
* g_pendingtasks.
*/
if (g_pendingtasks.head)
{
up_release_pending();
}
}
irqrestore(flags);
}
return OK;
}
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