forked from Archive/PX4-Autopilot
131 lines
4.7 KiB
C
131 lines
4.7 KiB
C
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/************************************************************************
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* sched/sched_unlock.c
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*
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* Copyright (C) 2007, 2009 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 <nuttx/arch.h>
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#include "os_internal.h"
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/************************************************************************
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* Definitions
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************************************************************************/
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/************************************************************************
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* Private Type Declarations
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************************************************************************/
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/************************************************************************
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* Global Variables
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************************************************************************/
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/************************************************************************
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* Private Variables
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************************************************************************/
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/************************************************************************
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* Private Function Prototypes
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************************************************************************/
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/************************************************************************
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* Private Functionss
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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: sched_unlock
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*
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* Description:
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* This function decrements the preemption lock count. Typically this
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* is paired with sched_lock() and concludes a critical section of
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* code. Preemption will not be unlocked until sched_unlock() has
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* been called as many times as sched_lock(). When the lockcount is
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* decremented to zero, any tasks that were eligible to preempt the
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* current task will execute.
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*
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************************************************************************/
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int sched_unlock(void)
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{
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_TCB *rtcb = (_TCB*)g_readytorun.head;
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/* Check for some special cases: (1) rtcb may be NULL only during
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* early boot-up phases, and (2) sched_unlock() should have no
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* effect if called from the interrupt level.
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*/
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if (rtcb && !up_interrupt_context())
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{
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/* Prevent context switches throughout the following */
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irqstate_t flags = irqsave();
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/* Decrement the preemption lock counter */
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if (rtcb->lockcount)
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{
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rtcb->lockcount--;
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}
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/* Check if the lock counter has decremented to zero. If so,
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* then pre-emption has been re-enabled.
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*/
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if (rtcb->lockcount <= 0)
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{
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rtcb->lockcount = 0;
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/* Release any ready-to-run tasks that have collected in
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* g_pendingtasks.
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*/
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if (g_pendingtasks.head)
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{
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up_release_pending();
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}
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}
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irqrestore(flags);
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}
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return OK;
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}
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