sem.c

xenomai 很好的linux实时补丁

 * - Kernel module initialization/cleanup code
 * - Interrupt service routine
 *   only if @a timeout is equal to TM_NONBLOCK.
 *
 * - Kernel-based task
 * - User-space task (switches to primary mode)
 *
 * Rescheduling: always unless the request is immediately satisfied or
 * @a timeout specifies a non-blocking operation.
 *
 * @note This service is sensitive to the current operation mode of
 * the system timer, as defined by the rt_timer_start() service. In
 * periodic mode, clock ticks are interpreted as periodic jiffies. In
 * oneshot mode, clock ticks are interpreted as nanoseconds.
 */

int rt_sem_p (RT_SEM *sem,
              RTIME timeout)
{
    int err = 0;
    spl_t s;

    xnlock_get_irqsave(&nklock,s);

    sem = xeno_h2obj_validate(sem,XENO_SEM_MAGIC,RT_SEM);

    if (!sem)
        {
        err = xeno_handle_error(sem,XENO_SEM_MAGIC,RT_SEM);
        goto unlock_and_exit;
        }
    
    if (timeout == TM_NONBLOCK)
        {
        if (sem->count > 0)
            sem->count--;
        else
            err = -EWOULDBLOCK;

        goto unlock_and_exit;
        }

    if (xnpod_unblockable_p())
	{
	err = -EPERM;
	goto unlock_and_exit;
	}

    if (sem->count > 0)
        --sem->count;
    else
        {
        RT_TASK *task = xeno_current_task();

        xnsynch_sleep_on(&sem->synch_base,timeout);
        
        if (xnthread_test_flags(&task->thread_base,XNRMID))
            err = -EIDRM; /* Semaphore deleted while pending. */
        else if (xnthread_test_flags(&task->thread_base,XNTIMEO))
            err = -ETIMEDOUT; /* Timeout.*/
        else if (xnthread_test_flags(&task->thread_base,XNBREAK))
            err = -EINTR; /* Unblocked.*/
        }

 unlock_and_exit:

    xnlock_put_irqrestore(&nklock,s);

    return err;
}

/**
 * @fn int rt_sem_v(RT_SEM *sem)
 * @brief Signal a semaphore.
 *
 * Release a semaphore unit. If the semaphore is pended, the first
 * waiting task (by queuing order) is immediately unblocked;
 * otherwise, the semaphore value is incremented by one.
 *
 * @param sem The descriptor address of the affected semaphore.
 *
 * @return 0 is returned upon success. Otherwise:
 *
 * - -EINVAL is returned if @a sem is not a semaphore descriptor.
 *
 * - -EIDRM is returned if @a sem is a deleted semaphore descriptor.
 *
 * Environments:
 *
 * This service can be called from:
 *
 * - Kernel module initialization/cleanup code
 * - Interrupt service routine
 * - Kernel-based task
 * - User-space task
 *
 * Rescheduling: possible.
 */

int rt_sem_v (RT_SEM *sem)

{
    int err = 0;
    spl_t s;

    xnlock_get_irqsave(&nklock,s);

    sem = xeno_h2obj_validate(sem,XENO_SEM_MAGIC,RT_SEM);

    if (!sem)
        {
        err = xeno_handle_error(sem,XENO_SEM_MAGIC,RT_SEM);
        goto unlock_and_exit;
        }
    
    if (xnsynch_wakeup_one_sleeper(&sem->synch_base) != NULL)
        xnpod_schedule();
    else if (!(sem->mode & S_PULSE))
        sem->count++;

 unlock_and_exit:

    xnlock_put_irqrestore(&nklock,s);

    return err;
}

/**
 * @fn int rt_sem_broadcast(RT_SEM *sem)
 * @brief Broadcast a semaphore.
 *
 * Unblock all tasks waiting on a semaphore. Awaken tasks return from
 * rt_sem_p() as if the semaphore has been signaled. The semaphore
 * count is zeroed as a result of the operation.
 *
 * @param sem The descriptor address of the affected semaphore.
 *
 * @return 0 is returned upon success. Otherwise:
 *
 * - -EINVAL is returned if @a sem is not a semaphore descriptor.
 *
 * - -EIDRM is returned if @a sem is a deleted semaphore descriptor.
 *
 * Environments:
 *
 * This service can be called from:
 *
 * - Kernel module initialization/cleanup code
 * - Interrupt service routine
 * - Kernel-based task
 * - User-space task
 *
 * Rescheduling: possible.
 */

int rt_sem_broadcast (RT_SEM *sem)

{
    int err = 0;
    spl_t s;

    xnlock_get_irqsave(&nklock,s);

    sem = xeno_h2obj_validate(sem,XENO_SEM_MAGIC,RT_SEM);

    if (!sem)
        {
        err = xeno_handle_error(sem,XENO_SEM_MAGIC,RT_SEM);
        goto unlock_and_exit;
        }

    if (xnsynch_flush(&sem->synch_base,0) == XNSYNCH_RESCHED)
	xnpod_schedule();

    sem->count = 0;

 unlock_and_exit:

    xnlock_put_irqrestore(&nklock,s);

    return err;
}

/**
 * @fn int rt_sem_inquire(RT_SEM *sem, RT_SEM_INFO *info)
 * @brief Inquire about a semaphore.
 *
 * Return various information about the status of a given semaphore.
 *
 * @param sem The descriptor address of the inquired semaphore.
 *
 * @param info The address of a structure the semaphore information
 * will be written to.

 * @return 0 is returned and status information is written to the
 * structure pointed at by @a info upon success. Otherwise:
 *
 * - -EINVAL is returned if @a sem is not a semaphore descriptor.
 *
 * - -EIDRM is returned if @a sem is a deleted semaphore descriptor.
 *
 * Environments:
 *
 * This service can be called from:
 *
 * - Kernel module initialization/cleanup code
 * - Interrupt service routine
 * - Kernel-based task
 * - User-space task
 *
 * Rescheduling: never.
 */

int rt_sem_inquire (RT_SEM *sem,
                    RT_SEM_INFO *info)
{
    int err = 0;
    spl_t s;

    xnlock_get_irqsave(&nklock,s);

    sem = xeno_h2obj_validate(sem,XENO_SEM_MAGIC,RT_SEM);

    if (!sem)
        {
        err = xeno_handle_error(sem,XENO_SEM_MAGIC,RT_SEM);
        goto unlock_and_exit;
        }
    
    strcpy(info->name,sem->name);
    info->count = sem->count;
    info->nwaiters = xnsynch_nsleepers(&sem->synch_base);

 unlock_and_exit:

    xnlock_put_irqrestore(&nklock,s);

    return err;
}

/**
 * @fn int rt_sem_bind(RT_SEM *sem,const char *name,RTIME timeout)
 * @brief Bind to a semaphore.
 *
 * This user-space only service retrieves the uniform descriptor of a
 * given Xenomai semaphore identified by its symbolic name. If the
 * semaphore does not exist on entry, this service blocks the caller
 * until a semaphore of the given name is created.
 *
 * @param name A valid NULL-terminated name which identifies the
 * semaphore to bind to.
 *
 * @param sem The address of a semaphore descriptor retrieved by the
 * operation. Contents of this memory is undefined upon failure.
 *
 * @param timeout The number of clock ticks to wait for the
 * registration to occur (see note). Passing TM_INFINITE causes the
 * caller to block indefinitely until the object is
 * registered. Passing TM_NONBLOCK causes the service to return
 * immediately without waiting if the object is not registered on
 * entry.
 *
 * @return 0 is returned upon success. Otherwise:
 *
 * - -EFAULT is returned if @a sem or @a name is referencing invalid
 * memory.
 *
 * - -EINTR is returned if rt_task_unblock() has been called for the
 * waiting task before the retrieval has completed.
 *
 * - -EWOULDBLOCK is returned if @a timeout is equal to TM_NONBLOCK
 * and the searched object is not registered on entry.
 *
 * - -ETIMEDOUT is returned if the object cannot be retrieved within
 * the specified amount of time.
 *
 * - -EPERM is returned if this service should block, but was called
 * from a context which cannot sleep (e.g. interrupt, non-realtime or
 * scheduler locked).
 *
 * Environments:
 *
 * This service can be called from:
 *
 * - User-space task (switches to primary mode)
 *
 * Rescheduling: always unless the request is immediately satisfied or
 * @a timeout specifies a non-blocking operation.
 *
 * @note This service is sensitive to the current operation mode of
 * the system timer, as defined by the rt_timer_start() service. In
 * periodic mode, clock ticks are interpreted as periodic jiffies. In
 * oneshot mode, clock ticks are interpreted as nanoseconds.
 */

/**
 * @fn int rt_sem_unbind(RT_SEM *sem)
 *
 * @brief Unbind from a semaphore.
 *
 * This user-space only service unbinds the calling task from the
 * semaphore object previously retrieved by a call to rt_sem_bind().
 *
 * @param sem The address of a semaphore descriptor to unbind from.
 *
 * @return 0 is always returned.
 *
 * This service can be called from:
 *
 * - User-space task.
 *
 * Rescheduling: never.
 */

int __native_sem_pkg_init (void)

{
    return 0;
}

void __native_sem_pkg_cleanup (void)

{
}

/*@}*/

EXPORT_SYMBOL(rt_sem_create);
EXPORT_SYMBOL(rt_sem_delete);
EXPORT_SYMBOL(rt_sem_p);
EXPORT_SYMBOL(rt_sem_v);
EXPORT_SYMBOL(rt_sem_inquire);
EXPORT_SYMBOL(rt_sem_broadcast);