nuttx/sched/sig_timedwait.c

/************************************************************
 * sig_timedwait.c
 *
 *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
 *
 * 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 Gregory Nutt 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 <sys/types.h>
#include <string.h>
#include <signal.h>
#include <time.h>
#include <wdog.h>
#include <assert.h>
#include <debug.h>
#include <sched.h>
#include <nuttx/arch.h>
#include "os_internal.h"
#include "sig_internal.h"
#include "clock_internal.h"

/************************************************************
 * Definitions
 ************************************************************/

/************************************************************
 * Private Type Declarations
 ************************************************************/

/************************************************************
 * Global Variables
 ************************************************************/

/************************************************************
 * Private Variables
 ************************************************************/

/************************************************************
 * Private Functionss
 ************************************************************/

/************************************************************
 * Function: sig_timeout
 *
 * Description:
 *  A timeout elapsed while waiting for signals to be queued.
 ************************************************************/

static void sig_timeout(int argc, uint32 itcb, ...)
{
  /* On many small machines, pointers are encoded and cannot
   * be simply cast from uint32 to _TCB*.  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
    {
      _TCB  *wtcb;
      uint32 itcb;
    } u;

   u.itcb = itcb;

  if (!u.wtcb)
    {
      PANIC(OSERR_TIMEOUTNOTCB);
    }

  /* 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 = ERROR;
      u.wtcb->sigunbinfo.si_code = SI_TIMEOUT;
      u.wtcb->sigunbinfo.si_value.sival_int = 0;
      up_unblock_task(u.wtcb);
    }
}

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

/************************************************************
 * Function: 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 in the si_code emember.  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_QUEUE   - Signal sent from sigqueue
 *     SI_MESGQ   - Signal generated by arrival of a message on an
 *                  empty message queue
 *     SI_NOWAIT  - Signal already pending -- don't know how sent
 *     SI_TIMEOUT - No Signal, restarted by timeout
 *
 * 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.
 *
 * Assumptions:
 *
 ************************************************************/

int sigtimedwait(const sigset_t *set, struct siginfo *info,
                 const struct timespec *timeout)
{
  _TCB          *rtcb = (_TCB*)g_readytorun.head;
  sigset_t       intersection;
  sigpendq_t    *sigpend;
  WDOG_ID        wdog;
  irqstate_t     saved_state;
  sint32         waitticks;
  int            ret = ERROR;

  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));
      if (!sigpend)
        {
          PANIC(OSERR_NOPENDINGSIGNAL);
        }

      /* 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 = 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 milliseconds */

          waitticks = MSEC2TICK(timeout->tv_sec  * MSEC_PER_SEC
                                + timeout->tv_nsec / NSEC_PER_MSEC);

          /* Create a watchdog */

          wdog = wd_create();
          if (wdog)
            {
              /* This little of nonsense is necessary for some
               * processors where sizeof(pointer) < sizeof(uint32).
               * see wdog.h.
               */

              wdparm_t wdparm;
              wdparm.pvarg = (void*)rtcb;

              /* Start the watchdog */

              wd_start(wdog, 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(wdog);
            }
        }

      /* 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.  Return the signal
       * info to the caller if so requested
       */

      if (info)
        {
          memcpy(info, &rtcb->sigunbinfo, sizeof(struct siginfo));
        }
      irqrestore(saved_state);

      /* The return value is the number of the signal that awakened us */

      ret = info->si_signo;
   }
   sched_unlock();

   return ret;
}