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nuttx-bb/nuttx/sched/sig_timedwait.c

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/****************************************************************************
* sched/sig_timedwait.c
*
* Copyright (C) 2007-2009, 2012 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 <stdint.h>
#include <string.h>
#include <signal.h>
#include <time.h>
#include <wdog.h>
#include <assert.h>
#include <debug.h>
#include <sched.h>
#include <errno.h>
#include <nuttx/arch.h>
#include "os_internal.h"
#include "sig_internal.h"
#include "clock_internal.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 Functionss
****************************************************************************/
/****************************************************************************
* 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 _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
{
FAR _TCB *wtcb;
uint32_t 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 = SIG_WAIT_TIMEOUT;
u.wtcb->sigunbinfo.si_code = SI_TIMER;
u.wtcb->sigunbinfo.si_value.sival_int = 0;
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 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_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 _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
sigset_t intersection;
FAR sigpendq_t *sigpend;
WDOG_ID wdog;
irqstate_t saved_state;
int32_t 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_t).
* see wdog.h.
*/
wdparm_t wdparm;
wdparm.pvarg = (FAR 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. 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;
}
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