129 lines
4.4 KiB
C
129 lines
4.4 KiB
C
/****************************************************************************
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* sched/semaphore/sem_waitirq.c
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*
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* Copyright (C) 2007-2010, 2014 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 <errno.h>
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#include <nuttx/arch.h>
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#include "semaphore/semaphore.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: sem_waitirq
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*
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* Description:
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* This function is called when either:
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*
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* 1. A signal is received by a task that is waiting on a semaphore.
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* According to the POSIX spec, "...the calling thread shall not return
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* from the call to [sem_wait] until it either locks the semaphore or
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* the call is interrupted by a signal."
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* 2. From logic associated with sem_timedwait(). This function is called
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* when the timeout elapses without receiving the semaphore.
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*
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* Parameters:
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* wtcb - A pointer to the TCB of the task that is waiting on a
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* semphaphore, but has received a signal or timeout instead.
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* errcode - EINTR if the semaphore wait was awakened by a signal;
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* ETIMEDOUT if awakened by a timeout
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*
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* Return Value:
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* None
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*
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* Assumptions:
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*
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****************************************************************************/
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void sem_waitirq(FAR struct tcb_s *wtcb, int errcode)
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{
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irqstate_t saved_state;
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/* Disable interrupts. This is necessary (unfortunately) because an
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* interrupt handler may attempt to post the semaphore while we are
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* doing this.
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*/
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saved_state = irqsave();
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/* It is possible that an interrupt/context switch beat us to the punch
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* and already changed the task's state.
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*/
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if (wtcb->task_state == TSTATE_WAIT_SEM)
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{
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sem_t *sem = wtcb->waitsem;
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DEBUGASSERT(sem != NULL && sem->semcount < 0);
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/* Restore the correct priority of all threads that hold references
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* to this semaphore.
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*/
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sem_canceled(wtcb, sem);
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/* And increment the count on the semaphore. This releases the count
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* that was taken by sem_post(). This count decremented the semaphore
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* count to negative and caused the thread to be blocked in the first
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* place.
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*/
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sem->semcount++;
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/* Indicate that the semaphore wait is over. */
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wtcb->waitsem = NULL;
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/* Mark the errno value for the thread. */
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wtcb->pterrno = errcode;
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/* Restart the task. */
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up_unblock_task(wtcb);
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}
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/* Interrupts may now be enabled. */
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irqrestore(saved_state);
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}
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