nuttx/sched/signal/sig_ppoll.c

/****************************************************************************
 * sched/signal/sig_ppoll.c
 *
 *   Copyright (C) 2018 Pinecone Inc. All rights reserved.
 *   Author: Xiang Xiao <xiaoxiang@pinecone.net>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <poll.h>

#include "sched/sched.h"
#include "signal/signal.h"

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: ppoll
 *
 * Description:
 *   ppoll() waits for one of a set of file descriptors to become ready to
 *   perform I/O.  If none of the events requested (and no error) has
 *   occurred for any of  the  file  descriptors,  then ppoll() blocks until
 *   one of the events occurs.
 *
 * Input Parameters:
 *   fds  - List of structures describing file descriptors to be monitored
 *   nfds - The number of entries in the list
 *   timeout - Specifies an upper limit on the time for which ppoll() will
 *     block.  A NULL pointer means an infinite timeout.
 *   sigmask - Replace the current signal mask temporarily during execution
 *
 * Returned Value:
 *   On success, the number of structures that have non-zero revents fields.
 *   A value of 0 indicates that the call timed out and no file descriptors
 *   were ready.  On error, -1 is returned, and errno is set appropriately:
 *
 *   EBADF  - An invalid file descriptor was given in one of the sets.
 *   EFAULT - The fds address is invalid
 *   EINTR  - A signal occurred before any requested event.
 *   EINVAL - The nfds value exceeds a system limit.
 *   ENOMEM - There was no space to allocate internal data structures.
 *   ENOSYS - One or more of the drivers supporting the file descriptor
 *     does not support the poll method.
 *
 ****************************************************************************/

int ppoll(FAR struct pollfd *fds, nfds_t nfds,
          FAR const struct timespec *timeout_ts,
          FAR const sigset_t *sigmask)
{
  FAR struct tcb_s *rtcb = this_task();
  sigset_t saved_sigprocmask;
  irqstate_t flags;
  int ret = ERROR;

  /* 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!
   */

  flags = enter_critical_section();

  /* Save a copy of the old sigprocmask and install
   * the new (temporary) sigprocmask
   */

  saved_sigprocmask = rtcb->sigprocmask;
  if (sigmask)
    {
      rtcb->sigprocmask = *sigmask;
    }

  rtcb->sigwaitmask = NULL_SIGNAL_SET;

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

  if (nxsig_unmask_pendingsignal())
    {
      /* Dispatching one or more of the signals is sufficient to cause
       * us to not wait. Restore the original sigprocmask.
       */

      rtcb->sigprocmask = saved_sigprocmask;
      leave_critical_section(flags);
      set_errno(EINTR);
    }
  else
    {
      int timeout = -1;

      /* And call poll to do the real work */

      if (timeout_ts)
        {
          timeout = timeout_ts->tv_sec * 1000 +
                    timeout_ts->tv_nsec / 1000000;
        }

      ret = poll(fds, nfds, timeout);

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

      rtcb->sigprocmask = saved_sigprocmask;
      leave_critical_section(flags);

      /* 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.
       */

      nxsig_unmask_pendingsignal();
    }

  return ret;
}