116 lines
3.7 KiB
C
116 lines
3.7 KiB
C
/****************************************************************************
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* sched/semaphore/sem_waitirq.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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/irq.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: nxsem_wait_irq
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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 [nxsem_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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* Input 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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* Returned 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 nxsem_wait_irq(FAR struct tcb_s *wtcb, int errcode)
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{
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irqstate_t flags;
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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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flags = enter_critical_section();
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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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nxsem_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->errcode = 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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leave_critical_section(flags);
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}
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