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1 jermar 1 
/*
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 * Copyright (C) 2001-2004 Jakub Jermar
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 * All rights reserved.
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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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 * - 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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 * - Redistributions in binary form must reproduce the above copyright
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 *   notice, this list of conditions and the following disclaimer in the
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 *   documentation and/or other materials provided with the distribution.
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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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/**
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 * @file    semaphore.c
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 * @brief   Semaphores.
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 */
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#include <synch/semaphore.h>
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#include <synch/waitq.h>
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#include <synch/spinlock.h>
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#include <synch/synch.h>
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#include <arch/asm.h>
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#include <arch.h>
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/** Initialize semaphore
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 *
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 * Initialize semaphore.
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 *
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 * @param s Semaphore.
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 * @param val Maximal number of threads allowed to enter critical section.
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 */
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void semaphore_initialize(semaphore_t *s, int val)
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{
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    ipl_t ipl;
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    waitq_initialize(&s->wq);
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    ipl = interrupts_disable();
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    spinlock_lock(&s->wq.lock);
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    s->wq.missed_wakeups = val;
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    spinlock_unlock(&s->wq.lock);
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    interrupts_restore(ipl);
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}
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/** Semaphore down
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 *
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 * Semaphore down.
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 * Conditional mode and mode with timeout can be requested.
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 *
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 * @param s Semaphore.
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 * @param usec Timeout in microseconds.
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 * @param flags Select mode of operation.
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 *
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 * For exact description of possible combinations of
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 * usec and flags, see comment for waitq_sleep_timeout().
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 *
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 * @return See comment for waitq_sleep_timeout().
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 */
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int _semaphore_down_timeout(semaphore_t *s, __u32 usec, int flags)
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{
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    return waitq_sleep_timeout(&s->wq, usec, flags);
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}
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/** Semaphore up
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 *
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 * Semaphore up.
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 *
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 * @param s Semaphore.
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 */
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void semaphore_up(semaphore_t *s)
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{
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    waitq_wakeup(&s->wq, WAKEUP_FIRST);
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}