text: /****************************************************************************
   * sched/signal/sig_timedwait.c
   *
   *   Copyright (C) 2007-2009, 2012-2014 Gregory Nutt. All rights reserved.
   *   Author: Gregory Nutt <gnutt@nuttx.org>
   *
   * 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 <nuttx/compiler.h>
  
  #include <stdint.h>
  #include <string.h>
  #include <signal.h>
  #include <time.h>
  #include <assert.h>
  #include <debug.h>
  #include <sched.h>
  #include <errno.h>
  
  #include <nuttx/arch.h>
  #include <nuttx/wdog.h>
  
  #include "sched/sched.h"
  #include "signal/signal.h"
  #include "clock/clock.h"
  
  /****************************************************************************
   * Pre-processor Definitions
   ****************************************************************************/
  
  /* This is a special value of si_signo that means that it was the timeout
   * that awakened the wait... not the receipt of a signal.
   */
  
  #define SIG_WAIT_TIMEOUT 0xff
  
  /****************************************************************************
   * Private Type Declarations
   ****************************************************************************/
  
  /****************************************************************************
   * Global Variables
   ****************************************************************************/
  
  /****************************************************************************
   * Private Variables
   ****************************************************************************/
  
  /****************************************************************************
   * Private Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: sig_timeout
   *
   * Description:
   *  A timeout elapsed while waiting for signals to be queued.
   *
   ****************************************************************************/
  
  static void sig_timeout(int argc, uint32_t itcb)
  {
    /* On many small machines, pointers are encoded and cannot be simply cast
     * from uint32_t to struct tcb_s*.  The following union works around this
     * (see wdogparm_t).  This odd logic could be conditioned on
     * CONFIG_CAN_CAST_POINTERS, but it is not too bad in any case.
     */
  
    union
      {
        FAR struct tcb_s *wtcb;
        uint32_t itcb;
      } u;
  
    u.itcb = itcb;
    ASSERT(u.wtcb);
  
    /* There may be a race condition -- make sure the task is
     * still waiting for a signal
     */
  
    if (u.wtcb->task_state == TSTATE_WAIT_SIG)
      {
        u.wtcb->sigunbinfo.si_signo           = SIG_WAIT_TIMEOUT;
        u.wtcb->sigunbinfo.si_code            = SI_TIMER;
        u.wtcb->sigunbinfo.si_value.sival_int = 0;
  #ifdef CONFIG_SCHED_HAVE_PARENT
        u.wtcb->sigunbinfo.si_pid             = 0;  /* Not applicable */
        u.wtcb->sigunbinfo.si_status          = OK;
  #endif
        up_unblock_task(u.wtcb);
      }
  }
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: sigtimedwait
   *
   * Description:
   *   This function selects the pending signal set specified by the argument
   *   set.  If multiple signals are pending in set, it will remove and return
   *   the lowest numbered one.  If no signals in set are pending at the time
   *   of the call, the calling process will be suspended until one of the
   *   signals in set becomes pending, OR until the process is interrupted by
   *   an unblocked signal, OR until the time interval specified by timeout
   *   (if any), has expired. If timeout is NULL, then the timeout interval
   *   is forever.
   *
   *   If the info argument is non-NULL, the selected signal number is stored
   *   in the si_signo member and the cause of the signal is store din the
   *   si_code member.  The content of si_value is only meaningful if the
   *   signal was generated by sigqueue().
   *
   *   The following values for si_code are defined in signal.h:
   *     SI_USER    - Signal sent from kill, raise, or abort
   *     SI_QUEUE   - Signal sent from sigqueue
   *     SI_TIMER   - Signal is result of timer expiration
   *     SI_ASYNCIO - Signal is the result of asynch IO completion
   *     SI_MESGQ   - Signal generated by arrival of a message on an
   *                  empty message queue.
   *
   * Parameters:
   *   set - The pending signal set.
   *   info - The returned value
   *   timeout - The amount of time to wait
   *
   * Return Value:
   *   Signal number that cause the wait to be terminated, otherwise -1 (ERROR)
   *   is returned with errno set to either:
   *
   *   EAGAIN - No signal specified by set was generated within the specified
   *            timeout period.
   *   EINTR  - The wait was interrupted by an unblocked, caught signal.
   *
   * Assumptions:
   *
   ****************************************************************************/
  
  int sigtimedwait(FAR const sigset_t *set, FAR struct siginfo *info,
                   FAR const struct timespec *timeout)
  {
    FAR struct tcb_s *rtcb = (FAR struct tcb_s*)g_readytorun.head;
    sigset_t intersection;
    FAR sigpendq_t *sigpend;
    irqstate_t saved_state;
    int32_t waitticks;
    int ret = ERROR;
  
    DEBUGASSERT(rtcb->waitdog == NULL);
  
    sched_lock();  /* Not necessary */
  
    /* 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!
     */
  
    saved_state = irqsave();
  
    /* Check if there is a pending signal corresponding to one of the
     * signals in the pending signal set argument.
     */
  
    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.
         */
  
        sigpend = sig_removependingsignal(rtcb, sig_lowest(&intersection));
        ASSERT(sigpend);
  
        /* Return the signal info to the caller if so requested */
  
        if (info)
          {
            memcpy(info, &sigpend->info, sizeof(struct siginfo));
          }
  
        /* Then dispose of the pending signal structure properly */
  
        sig_releasependingsignal(sigpend);
        irqrestore(saved_state);
  
        /* The return value is the number of the signal that awakened us */
  
        ret = sigpend->info.si_signo;
      }
  
    /* We will have to wait for a signal to be posted to this task. */
  
    else
      {
        /* Save the set of pending signals to wait for */
  
        rtcb->sigwaitmask = *set;
  
        /* Check if we should wait for the timeout */
  
        if (timeout)
          {
            /* Convert the timespec to system clock ticks, making sure that
             * the resulting delay is greater than or equal to the requested
             * time in nanoseconds.
             */
  
  #ifdef CONFIG_HAVE_LONG_LONG
            uint64_t waitticks64 = ((uint64_t)timeout->tv_sec * NSEC_PER_SEC +
                                    (uint64_t)timeout->tv_nsec + NSEC_PER_TICK - 1) /
                                    NSEC_PER_TICK;
            DEBUGASSERT(waitticks64 <= UINT32_MAX);
            waitticks = (uint32_t)waitticks64;
  #else
            uint32_t waitmsec;
  
            DEBUGASSERT(timeout->tv_sec < UINT32_MAX / MSEC_PER_SEC);
            waitmsec = timeout->tv_sec * MSEC_PER_SEC +
                      (timeout->tv_nsec + NSEC_PER_MSEC - 1) / NSEC_PER_MSEC;
            waitticks = MSEC2TICK(waitmsec);
  #endif
  
            /* Create a watchdog */
  
            rtcb->waitdog = wd_create();
            DEBUGASSERT(rtcb->waitdog);
  
            if (rtcb->waitdog)
              {
                /* This little bit of nonsense is necessary for some
                 * processors where sizeof(pointer) < sizeof(uint32_t).
                 * see wdog.h.
                 */
  
                wdparm_t wdparm;
                wdparm.pvarg = (FAR void *)rtcb;
  
                /* Start the watchdog */
  
                wd_start(rtcb->waitdog, waitticks, (wdentry_t)sig_timeout, 1,
                         wdparm.dwarg);
  
                /* Now wait for either the signal or the watchdog */
  
                up_block_task(rtcb, TSTATE_WAIT_SIG);
  
                /* We no longer need the watchdog */
  
                wd_delete(rtcb->waitdog);
                rtcb->waitdog = NULL;
              }
  
            /* REVISIT: And do what if there are no watchdog timers?  The wait
             * will fail and we will return something bogus.
             */
          }
  
        /* No timeout, just wait */
  
        else
          {
            /* And wait until one of the unblocked signals is posted */
  
            up_block_task(rtcb, TSTATE_WAIT_SIG);
          }
  
        /* We are running again, clear the sigwaitmask */
  
        rtcb->sigwaitmask = NULL_SIGNAL_SET;
  
        /* When we awaken, the cause will be in the TCB.  Get the signal number
         * or timeout) that awakened us.
         */
  
        if (GOOD_SIGNO(rtcb->sigunbinfo.si_signo))
          {
            /* We were awakened by a signal... but is it one of the signals that
             * we were waiting for?
             */
  
            if (sigismember(set, rtcb->sigunbinfo.si_signo))
              {
                /* Yes.. the return value is the number of the signal that
                 * awakened us.
                 */
  
                ret = rtcb->sigunbinfo.si_signo;
              }
            else
              {
                /* No... then set EINTR and report an error */
  
                set_errno(EINTR);
                ret = ERROR;
              }
          }
        else
          {
            /* Otherwise, we must have been awakened by the timeout.  Set EGAIN
             * and return an error.
             */
  
            DEBUGASSERT(rtcb->sigunbinfo.si_signo == SIG_WAIT_TIMEOUT);
            set_errno(EAGAIN);
            ret = ERROR;
          }
  
        /* Return the signal info to the caller if so requested */
  
        if (info)
          {
            memcpy(info, &rtcb->sigunbinfo, sizeof(struct siginfo));
          }
  
        irqrestore(saved_state);
     }
  
     sched_unlock();
     return ret;
  }
  