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semaphore.c

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/*!     \file kernel/semaphore.c
 *      \brief Mutex semaphores.
 *      \author Andrea Righi <drizzt@inwind.it>
 *      \date Last update: 2003-10-27
 *      \note Copyright (&copy;) 2003 Andrea Righi
 */

#include <const.h>
#include <arch/i386.h>
#include <kernel/task.h>
#include <kernel/semaphore.h>

//! \brief
//!     Initialize a semaphore variable.
//! \param sem The semaphore variable to initialize.
void INIT_MUTEX(semaphore_t *sem)
{
        atomic_set(sem, 1);
}

//! \brief
//!     Semaphore "down" function.
//! \param sem The semaphore variable.
void DOWN(semaphore_t *sem)
{
        dword IF = GET_IF();

        wait_for_wakeup:
        if ( atomic_read(sem) )
        {
                atomic_set(sem, 0);
        }
        else
        {
                enable();
                // Wait for a wake-up.
                idle();
                goto wait_for_wakeup;
        }
        SET_IF(IF);
}

//! \brief
//!     Semaphore "up" function.
//! \param sem The semaphore variable.
void UP(semaphore_t *sem)
{
        atomic_set(sem, 1);
}

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