FAR char *getcwd(FAR char *buf, size_t size)
{
  char *pwd;

  /* Verify input parameters */

#ifdef CONFIG_DEBUG
  if (!buf || !size)
    {
      set_errno(EINVAL);
      return NULL;
    }
#endif

  /* If no working directory is defined, then default to the home directory */

  pwd = getenv("PWD");
  if (!pwd)
    {
      pwd = CONFIG_LIB_HOMEDIR;
    }

  /* Verify that the cwd will fit into the user-provided buffer */

  if (strlen(pwd) + 1 > size)
    {
      set_errno(ERANGE);
      return NULL;
    }

  /* Copy the cwd to the user buffer */

  strcpy(buf, pwd);
  sched_unlock();
  return buf;
}

int px4_task_spawn_cmd(const char *name, int scheduler, int priority, int stack_size, main_t entry, char *const argv[])
{
	int pid;

	sched_lock();

	/* create the task */
	pid = task_create(name, priority, stack_size, entry, argv);

	if (pid > 0) {

		/* configure the scheduler */
		struct sched_param param;

		param.sched_priority = priority;
		sched_setscheduler(pid, scheduler, &param);

		/* XXX do any other private task accounting here before the task starts */
	}

	sched_unlock();

	return pid;
}

static int load_absmodule(FAR struct binary_s *bin)
{
  FAR struct binfmt_s *binfmt;
  int ret = -ENOENT;

  bdbg("Loading %s\n", bin->filename);

  /* Disabling pre-emption should be sufficient protection while accessing
   * the list of registered binary format handlers.
   */

  sched_lock();

  /* Traverse the list of registered binary format handlers.  Stop
   * when either (1) a handler recognized and loads the format, or
   * (2) no handler recognizes the format.
   */

  for (binfmt = g_binfmts; binfmt; binfmt = binfmt->next)
    {
      /* Use this handler to try to load the format */

      ret = binfmt->load(bin);
      if (ret == OK)
        {
          /* Successfully loaded -- break out with ret == 0 */

          bvdbg("Successfully loaded module %s\n", bin->filename);
          dump_module(bin);
          break;
        }
    }

  sched_unlock();
  return ret;
}

static void group_assigngid(FAR struct task_group_s *group)
{
	irqstate_t flags;
	gid_t gid;

	/* Pre-emption should already be enabled, but lets be paranoid careful */

	sched_lock();

	/* Loop until we create a unique ID */

	for (;;) {
		/* Increment the ID counter.  This is global data so be extra paranoid. */

		flags = irqsave();
		gid = ++g_gidcounter;

		/* Check for overflow */

		if (gid <= 0) {
			g_gidcounter = 1;
			irqrestore(flags);
		} else {
			/* Does a task group with this ID already exist? */

			irqrestore(flags);
			if (group_findbygid(gid) == NULL) {
				/* Now assign this ID to the group and return */

				group->tg_gid = gid;
				sched_unlock();
				return;
			}
		}
	}
}

/*
 * Deallocate memory region for specified address.
 *
 * The "addr" argument points to a memory region previously
 * allocated through a call to vm_allocate() or vm_map(). The
 * number of bytes freed is the number of bytes of the
 * allocated region. If one of the region of previous and next
 * are free, it combines with them, and larger free region is
 * created.
 */
int
vm_free(task_t task, void *addr)
{
	int err;

	sched_lock();
	if (!task_valid(task)) {
		err = ESRCH;
		goto out;
	}
	if (task != cur_task() && !task_capable(CAP_MEMORY)) {
		err = EPERM;
		goto out;
	}
	if (!user_area(addr)) {
		err = EFAULT;
		goto out;
	}

	err = do_free(task->map, addr);
 out:
	sched_unlock();
	return err;
}

int syslog_flush_intbuffer(FAR const struct syslog_channel_s *channel,
                           bool force)
{
  syslog_putc_t putfunc;
  int ch;
  int ret = OK;

  /* Select which putc function to use for this flush */

  putfunc = force ? channel->sc_putc : channel->sc_force;

  /* This logic is performed with the scheduler disabled to protect from
   * concurrent modification by other tasks.
   */

  sched_lock();
  do
    {
      /* Transfer one character to time.  This is inefficient, but is
       * done in this way to: (1) Deal with concurrent modification of
       * the interrupt buffer from interrupt activity, (2) Avoid keeper
       * interrupts disabled for a long time, and (3) to handler
       * wraparound of the circular buffer indices.
       */

      ch = syslog_remove_intbuffer();
      if (ch != EOF)
        {
          ret = putfunc(ch);
        }
    }
  while (ch != EOF && ret >= 0);

  sched_unlock();
  return ret;
}

int up_wdginitialize(void)
{
#if (defined(CONFIG_SAM34_WDT) && !defined(CONFIG_WDT_DISABLE_ON_RESET))
  int fd;
  int ret;

  /* Initialize tha register the watchdog timer device */

  wdgvdbg("Initializing Watchdog driver...\n");
  sam_wdtinitialize(CONFIG_WATCHDOG_DEVPATH);

  /* Open the watchdog device */

  wdgvdbg("Opening.\n");
  fd = open(CONFIG_WATCHDOG_DEVPATH, O_RDONLY);
  if (fd < 0)
    {
      wdgdbg("open %s failed: %d\n", CONFIG_WATCHDOG_DEVPATH, errno);
      goto errout;
    }

  /* Set the watchdog timeout */

  wdgvdbg("Timeout = %d.\n", CONFIG_WDT_TIMEOUT);
  ret = ioctl(fd, WDIOC_SETTIMEOUT, (unsigned long)CONFIG_WDT_TIMEOUT);
  if (ret < 0)
    {
      wdgdbg("ioctl(WDIOC_SETTIMEOUT) failed: %d\n", errno);
      goto errout_with_dev;
    }

  /* Set the watchdog minimum time */

  wdgvdbg("MinTime = %d.\n", CONFIG_WDT_MINTIME);
  ret = ioctl(fd, WDIOC_MINTIME, (unsigned long)CONFIG_WDT_MINTIME);
  if (ret < 0)
    {
      wdgdbg("ioctl(WDIOC_MINTIME) failed: %d\n", errno);
      goto errout_with_dev;
    }

  /* Start Kicker task */

#if defined(CONFIG_WDT_THREAD)
  sched_lock();

  int taskid = KERNEL_THREAD(CONFIG_WDT_THREAD_NAME,
                             CONFIG_WDT_THREAD_PRIORITY,
                             CONFIG_WDT_THREAD_STACKSIZE,
                             (main_t)wdog_daemon, (FAR char * const *)NULL);

  ASSERT(taskid > 0);
  sched_unlock();
#endif
  return OK;
errout_with_dev:
  close(fd);
errout:
  return ERROR;
#else
  return -ENODEV;
#endif
}

int aio_cancel(int fildes, FAR struct aiocb *aiocbp)
{
	FAR struct aio_container_s *aioc;
	FAR struct aio_container_s *next;
	int status;
	int ret;

	/* Check if a non-NULL aiocbp was provided */

	/* Lock the scheduler so that no I/O events can complete on the worker
	 * thread until we set complete this operation.
	 */

	ret = AIO_ALLDONE;
	sched_lock();
	aio_lock();

	if (aiocbp) {
		/* Check if the I/O has completed */

		if (aiocbp->aio_result == -EINPROGRESS) {
			/* No.. Find the container for this AIO control block */

			for (aioc = (FAR struct aio_container_s *)g_aio_pending.head; aioc && aioc->aioc_aiocbp != aiocbp; aioc = (FAR struct aio_container_s *)aioc->aioc_link.flink) ;

			/* Did we find a container for this fildes?  We should; the aio_result says
			 * that the transfer is pending.  If not we return AIO_ALLDONE.
			 */

			if (aioc) {
				/* Yes... attempt to cancel the I/O.  There are two
				 * possibilities:* (1) the work has already been started and
				 * is no longer queued, or (2) the work has not been started
				 * and is still in the work queue.  Only the second case can
				 * be cancelled.  work_cancel() will return -ENOENT in the
				 * first case.
				 */

				status = work_cancel(LPWORK, &aioc->aioc_work);
				if (status >= 0) {
					aiocbp->aio_result = -ECANCELED;
					ret = AIO_CANCELED;
				} else {
					ret = AIO_NOTCANCELED;
				}

				/* Remove the container from the list of pending transfers */

				(void)aioc_decant(aioc);
			}
		}
	} else {
		/* No aiocbp.. cancel all outstanding I/O for the fildes */

		next = (FAR struct aio_container_s *)g_aio_pending.head;
		do {
			/* Find the next container with this AIO control block */

			for (aioc = next; aioc && aioc->aioc_aiocbp->aio_fildes != fildes; aioc = (FAR struct aio_container_s *)aioc->aioc_link.flink) ;

			/* Did we find the container?  We should; the aio_result says
			 * that the transfer is pending.  If not we return AIO_ALLDONE.
			 */

			if (aioc) {
				/* Yes... attempt to cancel the I/O.  There are two
				 * possibilities:* (1) the work has already been started and
				 * is no longer queued, or (2) the work has not been started
				 * and is still in the work queue.  Only the second case can
				 * be cancelled.  work_cancel() will return -ENOENT in the
				 * first case.
				 */

				status = work_cancel(LPWORK, &aioc->aioc_work);

				/* Remove the container from the list of pending transfers */

				next = (FAR struct aio_container_s *)aioc->aioc_link.flink;
				aiocbp = aioc_decant(aioc);
				DEBUGASSERT(aiocbp);

				if (status >= 0) {
					aiocbp->aio_result = -ECANCELED;
					if (ret != AIO_NOTCANCELED) {
						ret = AIO_CANCELED;
					}
				} else {
					ret = AIO_NOTCANCELED;
				}
			}
		} while (aioc);
	}

	aio_unlock();
	sched_unlock();
	return ret;
}

void uipdriver_loop(void)
{
  /* netdev_read will return 0 on a timeout event and >0 on a data received event */

  g_sim_dev.d_len = netdev_read((unsigned char*)g_sim_dev.d_buf, CONFIG_NET_BUFSIZE);

  /* Disable preemption through to the following so that it behaves a little more
   * like an interrupt (otherwise, the following logic gets pre-empted an behaves
   * oddly.
   */

  sched_lock();
  if (g_sim_dev.d_len > 0)
    {
      /* Data received event.  Check for valid Ethernet header with destination == our
       * MAC address
       */

      if (g_sim_dev.d_len > UIP_LLH_LEN && up_comparemac(BUF->ether_dhost, &g_sim_dev.d_mac) == 0)
        {
          /* We only accept IP packets of the configured type and ARP packets */

#ifdef CONFIG_NET_IPv6
          if (BUF->ether_type == htons(UIP_ETHTYPE_IP6))
#else
          if (BUF->ether_type == htons(UIP_ETHTYPE_IP))
#endif
            {
              uip_arp_ipin(&g_sim_dev);
              uip_input(&g_sim_dev);

             /* If the above function invocation resulted in data that
              * should be sent out on the network, the global variable
              * d_len is set to a value > 0.
              */

              if (g_sim_dev.d_len > 0)
                {
                  uip_arp_out(&g_sim_dev);
                  netdev_send(g_sim_dev.d_buf, g_sim_dev.d_len);
                }
            }
          else if (BUF->ether_type == htons(UIP_ETHTYPE_ARP))
            {
              uip_arp_arpin(&g_sim_dev);

              /* If the above function invocation resulted in data that
               * should be sent out on the network, the global variable
               * d_len is set to a value > 0.
               */

              if (g_sim_dev.d_len > 0)
                {
                  netdev_send(g_sim_dev.d_buf, g_sim_dev.d_len);
                }
            }
        }
    }

  /* Otherwise, it must be a timeout event */

  else if (timer_expired(&g_periodic_timer))
    {
      timer_reset(&g_periodic_timer);
      uip_timer(&g_sim_dev, sim_uiptxpoll, 1);
    }
  sched_unlock();
}

int sigsuspend(FAR const sigset_t *set)
{
  FAR struct tcb_s *rtcb = (FAR struct tcb_s *)g_readytorun.head;
  sigset_t intersection;
  sigset_t saved_sigprocmask;
  FAR sigpendq_t *sigpend;
  irqstate_t saved_state;
  int unblocksigno;

  /* Several operations must be performed below:  We must determine if any
   * signal is pending and, if not, wait for the signal.  Since signals can
   * be posted from the interrupt level, there is a race condition that
   * can only be eliminated by disabling interrupts!
   */

  sched_lock();  /* Not necessary */
  saved_state = irqsave();

  /* Check if there is a pending signal corresponding to one of the
   * signals that will be unblocked by the new sigprocmask.
   */

  intersection = ~(*set) & sig_pendingset(rtcb);
  if (intersection != NULL_SIGNAL_SET)
    {
      /* One or more of the signals in intersections is sufficient to cause
       * us to not wait.  Pick the lowest numbered signal and mark it not
       * pending.
       */

      unblocksigno = sig_lowest(&intersection);
      sigpend = sig_removependingsignal(rtcb, unblocksigno);
      ASSERT(sigpend);

      sig_releasependingsignal(sigpend);
      irqrestore(saved_state);
    }
  else
    {
      /* Its time to wait. Save a copy of the old sigprocmask and install
       * the new (temporary) sigprocmask
       */

      saved_sigprocmask = rtcb->sigprocmask;
      rtcb->sigprocmask = *set;
      rtcb->sigwaitmask = NULL_SIGNAL_SET;

      /* And wait until one of the unblocked signals is posted */

      up_block_task(rtcb, TSTATE_WAIT_SIG);

      /* We are running again, restore the original sigprocmask */

      rtcb->sigprocmask = saved_sigprocmask;
      irqrestore(saved_state);

      /* Now, handle the (rare?) case where (a) a blocked signal was received
       * while the task was suspended but (b) restoring the original
       * sigprocmask will unblock the signal.
       */

      sig_unmaskpendingsignal();
    }

  sched_unlock();
  return ERROR;
}

//.........这里部分代码省略.........

      switch (newstate)
        {
        case PM_NORMAL:
          {
            /* If we just awakened from PM_STANDBY mode, then reconfigure
             * clocking.
             */

            if (oldstate == PM_STANDBY)
              {
                /* Re-enable clocking */

                stm32_clockenable();

                /* The system timer was disabled while in PM_STANDBY or
                 * PM_SLEEP modes.  But the RTC has still be running:  Reset
                 * the system time the current RTC time.
                 */

#ifdef CONFIG_RTC
                clock_synchronize();
#endif
              }
          }
          break;

        case PM_IDLE:
          {
          }
          break;

        case PM_STANDBY:
          {
            /* Set the alarm as an EXTI Line */

#ifdef CONFIG_RTC_ALARM
            stm32_rtc_alarm(CONFIG_PM_ALARM_SEC, CONFIG_PM_ALARM_NSEC, true);
#endif
            /* Wait 10ms */

            up_mdelay(10);

            /* Enter the STM32 stop mode */

            (void)stm32_pmstop(false);

            /* We have been re-awakened by some even:  A button press?
             * An alarm?  Cancel any pending alarm and resume the normal
             * operation.
             */

#ifdef CONFIG_RTC_ALARM
            stm32_exti_cancel();
            ret = stm32_rtc_cancelalarm();
            if (ret < 0)
              {
                lldbg("Warning: Cancel alarm failed\n");
              }
#endif
            /* Note:  See the additional PM_STANDBY related logic at the
             * beginning of this function.  That logic is executed after
             * this point.
             */
          }
          break;

        case PM_SLEEP:
          {
            /* We should not return from standby mode.  The only way out
             * of standby is via the reset path.
             */

            /* Configure the RTC alarm to Auto Reset the system */

#ifdef CONFIG_PM_SLEEP_WAKEUP
            stm32_rtc_alarm(CONFIG_PM_SLEEP_WAKEUP_SEC, CONFIG_PM_SLEEP_WAKEUP_NSEC, false);
#endif
            /* Wait 10ms */

            up_mdelay(10);

            /* Enter the STM32 standby mode */

            (void)stm32_pmstandby();
          }
          break;

        default:
          break;
        }

      /* Save the new state */

      oldstate = newstate;

errout:
      sched_unlock();
    }
}

int pthread_mutex_unlock(FAR pthread_mutex_t *mutex)
{
  int ret = OK;

  sdbg("mutex=0x%p\n", mutex);

  if (!mutex)
    {
      ret = EINVAL;
    }
  else
    {
      /* Make sure the semaphore is stable while we make the following
       * checks.  This all needs to be one atomic action.
       */

      sched_lock();

      /* Does the calling thread own the semaphore? */

      if (mutex->pid != (int)getpid())
        {
          /* No... return an error (default behavior is like PTHREAD_MUTEX_ERRORCHECK) */

          sdbg("Holder=%d returning EPERM\n", mutex->pid);
          ret = EPERM;
        }


      /* Yes, the caller owns the semaphore.. Is this a recursive mutex? */

#ifdef CONFIG_MUTEX_TYPES
      else if (mutex->type == PTHREAD_MUTEX_RECURSIVE && mutex->nlocks > 1)
        {
          /* This is a recursive mutex and we there are multiple locks held. Retain
           * the mutex lock, just decrement the count of locks held, and return
           * success.
           */
          mutex->nlocks--;
        }
#endif

      /* This is either a non-recursive mutex or is the outermost unlock of
       * a recursive mutex.
       */

      else
        {
          /* Nullify the pid and lock count then post the semaphore */

          mutex->pid    = -1;
#ifdef CONFIG_MUTEX_TYPES
          mutex->nlocks = 0;
#endif
          ret = pthread_givesemaphore((sem_t*)&mutex->sem);
        }
      sched_unlock();
    }

  sdbg("Returning %d\n", ret);
  return ret;
}

int task_restart(pid_t pid)
{
  FAR _TCB  *rtcb;
  FAR _TCB  *tcb;
  int        status;
  irqstate_t state;

  /* Make sure this task does not become ready-to-run while
   * we are futzing with its TCB
   */

  sched_lock();

  /* Check if the task to restart is the calling task */

  rtcb = (FAR _TCB*)g_readytorun.head;
  if ((pid == 0) || (pid == rtcb->pid))
    {
      /* Not implemented */

      return ERROR;
    }

  /* We are restarting some other task than ourselves */

  else
    {
      /* Find for the TCB associated with matching pid  */

      tcb = sched_gettcb(pid);
      if (!tcb)
        {
          /* There is no TCB with this pid */

          return ERROR;
        }

      /* Remove the TCB from whatever list it is in.  At this point, the
       * TCB should no longer be accessible to the system 
       */

      state = irqsave();
      dq_rem((FAR dq_entry_t*)tcb, (dq_queue_t*)g_tasklisttable[tcb->task_state].list);
      tcb->task_state = TSTATE_TASK_INVALID;
      irqrestore(state);

      /* Deallocate anything left in the TCB's queues */

      sig_cleanup(tcb); /* Deallocate Signal lists */

      /* Reset the current task priority  */

      tcb->sched_priority = tcb->init_priority;

      /* Reset the base task priority and the number of pending reprioritizations */

#ifdef CONFIG_PRIORITY_INHERITANCE
      tcb->base_priority  = tcb->init_priority;
#  if CONFIG_SEM_NNESTPRIO > 0
      tcb->npend_reprio   = 0;
#  endif
#endif

      /* Re-initialize the processor-specific portion of the TCB
       * This will reset the entry point and the start-up parameters
       */

      up_initial_state(tcb);

      /* Add the task to the inactive task list */

      dq_addfirst((FAR dq_entry_t*)tcb, (dq_queue_t*)&g_inactivetasks);
      tcb->task_state = TSTATE_TASK_INACTIVE;

      /* Activate the task */

      status = task_activate(tcb);
      if (status != OK)
        {
          dq_rem((FAR dq_entry_t*)tcb, (dq_queue_t*)&g_inactivetasks);
          sched_releasetcb(tcb);
          return ERROR;
        }
    }

  sched_unlock();
  return OK;
}

void nxcon_kbdin(NXCONSOLE handle, FAR const uint8_t *buffer, uint8_t buflen)
{
  FAR struct nxcon_state_s *priv;
  ssize_t nwritten;
  int nexthead;
  char ch;
  int ret;

  gvdbg("buflen=%d\n");
  DEBUGASSERT(handle);

  /* Get the reference to the driver structure from the handle */

  priv = (FAR struct nxcon_state_s *)handle;

  /* Get exclusive access to the driver structure */

  ret = nxcon_semwait(priv);
  if (ret < 0)
    {
      gdbg("ERROR: nxcon_semwait failed\n");
      return;
    }

 /* Loop until all of the bytes have been written.  This function may be
  * called from an interrupt handler!  Semaphores cannot be used!
  *
  * The write logic only needs to modify the head index.  Therefore,
  * there is a difference in the way that head and tail are protected:
  * tail is protected with a semaphore; tail is protected by disabling
  * interrupts.
  */

  for (nwritten = 0; nwritten < buflen; nwritten++)
    {
      /* Add the next character */

      ch = buffer[nwritten];

      /* Calculate the write index AFTER the next byte is add to the ring
       * buffer
       */

      nexthead = priv->head + 1;
      if (nexthead >= CONFIG_NXCONSOLE_KBDBUFSIZE)
        {
          nexthead = 0;
        }

      /* Would the next write overflow the circular buffer? */

      if (nexthead == priv->tail)
        {
          /* Yes... Return an indication that nothing was saved in the buffer. */

          gdbg("ERROR: Keyboard data overrun\n");
          break;
        }

      /* No... copy the byte */

      priv->rxbuffer[priv->head] = ch;
      priv->head = nexthead;
    }

  /* Was anything written? */

  if (nwritten > 0)
    {
      int i;

      /* Are there threads waiting for read data? */

      sched_lock();
      for (i = 0; i < priv->nwaiters; i++)
        {
          /* Yes.. Notify all of the waiting readers that more data is available */

          sem_post(&priv->waitsem);
        }

      /* Notify all poll/select waiters that they can write to the FIFO */

#ifndef CONFIG_DISABLE_POLL
      nxcon_pollnotify(priv, POLLIN);
#endif
      sched_unlock();
    }

  nxcon_sempost(priv);
}

ssize_t nxcon_read(FAR struct file *filep, FAR char *buffer, size_t len)
{
  FAR struct nxcon_state_s *priv;
  ssize_t nread;
  char ch;
  int ret;

  /* Recover our private state structure */

  DEBUGASSERT(filep && filep->f_priv);
  priv = (FAR struct nxcon_state_s *)filep->f_priv;

  /* Get exclusive access to the driver structure */

  ret = nxcon_semwait(priv);
  if (ret < 0)
    {
      gdbg("ERROR: nxcon_semwait failed\n");
      return ret;
    }

  /* Loop until something is read */

  for (nread = 0; nread < len; )
    {
      /* Get the next byte from the buffer */

      if (priv->head == priv->tail)
        {
          /* The circular buffer is empty. Did we read anything? */

          if (nread > 0)
            {
              /* Yes.. break out to return what we have.  */

              break;
            }

          /* If the driver was opened with O_NONBLOCK option, then don't wait.
           * Just return EGAIN.
           */

          if (filep->f_oflags & O_NONBLOCK)
            {
              nread = -EAGAIN;
              break;
            }

          /* Otherwise, wait for something to be written to the circular
           * buffer. Increment the number of waiters so that the nxcon_write()
           * will not that it needs to post the semaphore to wake us up.
           */

          sched_lock();
          priv->nwaiters++;
          nxcon_sempost(priv);

          /* We may now be pre-empted!  But that should be okay because we
           * have already incremented nwaiters.  Pre-emption is disabled
           * but will be re-enabled while we are waiting.
           */

          ret = sem_wait(&priv->waitsem);

          /* Pre-emption will be disabled when we return.  So the decrementing
           * nwaiters here is safe.
           */

          priv->nwaiters--;
          sched_unlock();

          /* Did we successfully get the waitsem? */

          if (ret >= 0)
            {
              /* Yes... then retake the mutual exclusion semaphore */

              ret = nxcon_semwait(priv);
            }

          /* Was the semaphore wait successful? Did we successful re-take the
           * mutual exclusion semaphore?
           */

          if (ret < 0)
            {
              /* No.. One of the two sem_wait's failed. */

              int errval = errno;

              gdbg("ERROR: nxcon_semwait failed\n");

              /* Were we awakened by a signal?  Did we read anything before
               * we received the signal?
               */

              if (errval != EINTR || nread >= 0)
                {
                  /* Yes.. return the error. */

//.........这里部分代码省略.........

//.........这里部分代码省略.........
      /* Don't wait if all if no I/O was queue */

      if (nqueued > 0)
        {
          /* Wait until all I/O completes.  The scheduler will be unlocked
           * while we are waiting.
           */

          status = lio_waitall(list, nent);
          if (status < 0 && ret == OK)
            {
              /* Something bad happened while waiting and this is the first
               * error to be reported.
               */

              retcode = -status;
              ret     = ERROR;
            }
        }
    }

  /* Case 2: mode == LIO_NOWAIT and sig != NULL
   *
   *   If any I/O was queued, then setup to signal the caller when all of
   *   the transfers complete.
   *
   *   If no I/O was queue, then we I suppose that we need to signal the
   *   caller ourself?
   */

  else if (sig && sig->sigev_notify == SIGEV_SIGNAL)
    {
      if (nqueued > 0)
        {
          /* Setup a signal handler to detect when until all I/O completes. */

          status = lio_sigsetup(list, nent, sig);
          if (status < 0 && ret == OK)
            {
              /* Something bad happened while setting up the signal and this
               * is the first error to be reported.
               */

              retcode = -status;
              ret     = ERROR;
            }
        }
      else
        {
#ifdef CONFIG_CAN_PASS_STRUCTS
          status = sigqueue(getpid(), sig->sigev_signo,
                            sig->sigev_value);
#else
          status = sigqueue(getpid(), sig->sigev_signo,
                            sig->sigev_value.sival_ptr);
#endif
          if (status < 0 && ret == OK)
            {
              /* Something bad happened while signalling ourself and this is
               * the first error to be reported.
               */

              retcode = get_errno();
              ret     = ERROR;
            }
        }
    }

#ifdef CONFIG_SIG_EVTHREAD
  /* Notify the client via a function call */

  else if (sig && sig->sigev_notify == SIGEV_THREAD)
    {
      status = sig_notification(sighand->pid, &sighand->sig);
      if (status < 0 && ret == OK)
        {
         /* Something bad happened while performing the notification
          * and this is the first error to be reported.
          */

          retcode = -status;
          ret     = ERROR;
        }
    }
#endif

  /* Case 3: mode == LIO_NOWAIT and sig == NULL
   *
   *   Just return now.
   */

  sched_unlock();
  if (ret < 0)
    {
      set_errno(retcode);
      return ERROR;
    }

  return OK;
}

int sched_getparam (pid_t pid, FAR struct sched_param *param)
{
  FAR struct tcb_s *rtcb;
  FAR struct tcb_s *tcb;
  int ret = OK;

  if (!param)
    {
      return ERROR;
    }

  /* Check if the task to restart is the calling task */

  rtcb = (FAR struct tcb_s *)g_readytorun.head;
  if ((pid == 0) || (pid == rtcb->pid))
    {
      /* Return the priority if the calling task. */

      param->sched_priority = (int)rtcb->sched_priority;
    }

  /* Ths pid is not for the calling task, we will have to look it up */

  else
    {
      /* Get the TCB associated with this pid */

      sched_lock();
      tcb = sched_gettcb(pid);
      if (!tcb)
        {
          /* This pid does not correspond to any known task */

          ret = ERROR;
        }
      else
        {
#ifdef CONFIG_SCHED_SPORADIC
#endif
          /* Return the priority of the task */

          param->sched_priority = (int)tcb->sched_priority;

#ifdef CONFIG_SCHED_SPORADIC
          if ((tcb->flags & TCB_FLAG_POLICY_MASK) == TCB_FLAG_SCHED_SPORADIC)
            {
              FAR struct sporadic_s *sporadic = tcb->sporadic;
              DEBUGASSERT(sporadic != NULL);

              /* Return parameters associated with SCHED_SPORADIC */

              param->sched_ss_low_priority = (int)sporadic->low_priority;
              param->sched_ss_max_repl     = (int)sporadic->max_repl;

              clock_ticks2time((int)sporadic->repl_period, &param->sched_ss_repl_period);
              clock_ticks2time((int)sporadic->budget, &param->sched_ss_init_budget);
            }
          else
            {
              param->sched_ss_low_priority        = 0;
              param->sched_ss_max_repl            = 0;
              param->sched_ss_repl_period.tv_sec  = 0;
              param->sched_ss_repl_period.tv_nsec = 0;
              param->sched_ss_init_budget.tv_sec  = 0;
              param->sched_ss_init_budget.tv_nsec = 0;
            }
#endif
        }

      sched_unlock();
    }

  return ret;
}

//.........这里部分代码省略.........
   * message. Each is list is maintained in ascending priority order.
   */

  for (prev = NULL, next = (FAR struct mqueue_msg_s *)msgq->msglist.head;
       next && prio <= next->priority;
       prev = next, next = next->next);

  /* Add the message at the right place */

  if (prev)
    {
      sq_addafter((FAR sq_entry_t *)prev, (FAR sq_entry_t *)mqmsg,
                  &msgq->msglist);
    }
  else
    {
      sq_addfirst((FAR sq_entry_t *)mqmsg, &msgq->msglist);
    }

  /* Increment the count of messages in the queue */

  msgq->nmsgs++;
  irqrestore(saved_state);

  /* Check if we need to notify any tasks that are attached to the
   * message queue
   */

#ifndef CONFIG_DISABLE_SIGNALS
  if (msgq->ntmqdes)
    {
      struct sigevent event;
      pid_t pid;

      /* Remove the message notification data from the message queue. */

      memcpy(&event, &msgq->ntevent, sizeof(struct sigevent));
      pid = msgq->ntpid;

      /* Detach the notification */

      memset(&msgq->ntevent, 0, sizeof(struct sigevent));
      msgq->ntpid   = INVALID_PROCESS_ID;
      msgq->ntmqdes = NULL;

      /* Notification the client via signal? */

      if (event.sigev_notify == SIGEV_SIGNAL)
        {
          /* Yes... Queue the signal -- What if this returns an error? */

#ifdef CONFIG_CAN_PASS_STRUCTS
          DEBUGVERIFY(sig_mqnotempty(pid, event.sigev_signo,
                      event.sigev_value));
#else
          DEBUGVERIFY(sig_mqnotempty(pid, event.sigev_signo,
                      event.sigev_value.sival_ptr));
#endif
        }

#ifdef CONFIG_SIG_EVTHREAD
      /* Notify the client via a function call */

      else if (event.sigev_notify == SIGEV_THREAD)
        {
          DEBUGVERIFY(sig_notification(pid, &event));
        }
#endif

    }
#endif

  /* Check if any tasks are waiting for the MQ not empty event. */

  saved_state = irqsave();
  if (msgq->nwaitnotempty > 0)
    {
      /* Find the highest priority task that is waiting for
       * this queue to be non-empty in g_waitingformqnotempty
       * list. sched_lock() should give us sufficent protection since
       * interrupts should never cause a change in this list
       */

      for (btcb = (FAR struct tcb_s *)g_waitingformqnotempty.head;
           btcb && btcb->msgwaitq != msgq;
           btcb = btcb->flink);

      /* If one was found, unblock it */

      ASSERT(btcb);

      btcb->msgwaitq = NULL;
      msgq->nwaitnotempty--;
      up_unblock_task(btcb);
    }

  irqrestore(saved_state);
  sched_unlock();
  return OK;
}

int mq_close(mqd_t mqdes)
{
  FAR _TCB    *rtcb = (FAR _TCB*)g_readytorun.head;
  FAR msgq_t *msgq;
  irqstate_t  saved_state;
  int         ret = ERROR;

  /* Verify the inputs */

   if (mqdes)
     {
       sched_lock();

       /* Remove the message descriptor from the current task's
        * list of message descriptors.
        */

       sq_rem((FAR sq_entry_t*)mqdes, &rtcb->msgdesq);

       /* Find the message queue associated with the message descriptor */

       msgq = mqdes->msgq;

       /* Check if the calling task has a notification attached to
        * the message queue via this mqdes.
        */

#ifndef CONFIG_DISABLE_SIGNALS
       if (msgq->ntmqdes == mqdes)
         {
           msgq->ntpid   = INVALID_PROCESS_ID;
           msgq->ntsigno = 0;
           msgq->ntvalue.sival_int = 0;
           msgq->ntmqdes = NULL;
         }
#endif

       /* Decrement the connection count on the message queue. */

       if (msgq->nconnect)
         {
           msgq->nconnect--;
         }

       /* If it is no longer connected to any message descriptor and if the
        * message queue has already been unlinked, then we can discard the
        * message queue.
        */

       if (!msgq->nconnect && msgq->unlinked)
         {
           /* Remove the message queue from the list of all
            * message queues
            */

           saved_state = irqsave();
           (void)sq_rem((FAR sq_entry_t*)msgq, &g_msgqueues);
           irqrestore(saved_state);

           /* Then deallocate it (and any messages left in it) */

           mq_msgqfree(msgq);
         }

       /* Deallocate the message descriptor */

       mq_desfree(mqdes);

       sched_unlock();
       ret = OK;
     }

   return ret;
}

//.........这里部分代码省略.........

  sched_lock();

  /* Verify that this task actually has children and that the the requeste
   * TCB is actually a child of this task.
   */

  if (rtcb->nchildren == 0)
    {
      err = ECHILD;
      goto errout_with_errno;
    }
  else if (idtype == P_PID)
    {
     /* Get the TCB corresponding to this PID and make sure it is our child. */

      FAR _TCB *ctcb = sched_gettcb((pid_t)id);
      if (!ctcb || ctcb->parent != rtcb->pid)
        {
          err = ECHILD;
          goto errout_with_errno;
        }
    }

  /* Loop until the child that we are waiting for dies */

  for (;;)
    {
      /* Check if the task has already died. Signals are not queued in
       * NuttX.  So a possibility is that the child has died and we
       * missed the death of child signal (we got some other signal
       * instead).
       */

      if (rtcb->nchildren == 0 ||
          (idtype == P_PID && (ret = kill((pid_t)id, 0)) < 0))
        {
          /* We know that the child task was running okay we stared,
           * so we must have lost the signal.  What can we do?
           * Let's claim we were interrupted by a signal.
           */

          err = EINTR;
          goto errout_with_errno;
        }

      /* Wait for any death-of-child signal */

      ret = sigwaitinfo(&sigset, info);
      if (ret < 0)
        {
          goto errout;
        }

      /* Make there this was SIGCHLD */

      if (info->si_signo == SIGCHLD)
        {
          /* Yes.. Are we waiting for the death of a specific child? */

          if (idtype == P_PID)
            {
              /* Was this the death of the thread we were waiting for? */

              if (info->si_pid == (pid_t)id)
                {
                   /* Yes... return success */

                   break;
                }
            }

          /* Are we waiting for any child to change state? */

          else if (idtype == P_ALL)
            {
              /* Return success */

              break;
            }

          /* Other ID types are not supported */

          else /* if (idtype == P_PGID) */
            {
              set_errno(ENOSYS);
              goto errout;
            }
        }
    }

  sched_unlock();
  return OK;

errout_with_errno:
  set_errno(err);
errout:
  sched_unlock();
  return ERROR;
}