/****************************************************************************
* sched/signal/sig_timedwait.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* 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/irq.h>
#include <nuttx/arch.h>
#include <nuttx/wdog.h>
#include <nuttx/signal.h>
#include <nuttx/cancelpt.h>
#include <nuttx/queue.h>
#include "sched/sched.h"
#include "signal/signal.h"
#include "clock/clock.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* These are special values of si_signo that mean that either the wait was
* awakened with a timeout, or the wait was canceled... not the receipt of a
* signal.
*/
#define SIG_CANCEL_TIMEOUT 0xfe
#define SIG_WAIT_TIMEOUT 0xff
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: nxsig_timeout
*
* Description:
* A timeout elapsed while waiting for signals to be queued.
*
* Assumptions:
* This function executes in the context of the timer interrupt handler.
* Local interrupts are assumed to be disabled on entry.
*
****************************************************************************/
static void nxsig_timeout(wdparm_t arg)
{
FAR struct tcb_s *wtcb = (FAR struct tcb_s *)(uintptr_t)arg;
#ifdef CONFIG_SMP
irqstate_t flags;
/* We must be in a critical section in order to call up_switch_context()
* below. If we are running on a single CPU architecture, then we know
* interrupts a disabled an there is no need to explicitly call
* enter_critical_section(). However, in the SMP case,
* enter_critical_section() does much more than just disable interrupts on
* the local CPU; it also manages spinlocks to assure the stability of the
* TCB that we are manipulating.
*/
flags = enter_critical_section();
#endif
/* There may be a race condition -- make sure the task is
* still waiting for a signal
*/
if (wtcb->task_state == TSTATE_WAIT_SIG)
{
FAR struct tcb_s *rtcb = this_task();
wtcb->sigunbinfo.si_signo = SIG_WAIT_TIMEOUT;
wtcb->sigunbinfo.si_code = SI_TIMER;
wtcb->sigunbinfo.si_errno = ETIMEDOUT;
wtcb->sigunbinfo.si_value.sival_int = 0;
#ifdef CONFIG_SCHED_HAVE_PARENT
wtcb->sigunbinfo.si_pid = 0; /* Not applicable */
wtcb->sigunbinfo.si_status = OK;
#endif
/* Remove the task from waitting list */
dq_rem((FAR dq_entry_t *)wtcb, &g_waitingforsignal);
/* Add the task to ready-to-run task list, and
* perform the context switch if one is needed
*/
if (nxsched_add_readytorun(wtcb))
{
up_switch_context(wtcb, rtcb);
}
}
#ifdef CONFIG_SMP
leave_critical_section(flags);
#endif
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: nxsig_wait_irq
*
* Description:
* An error event has occurred and the signal wait must be terminated with
* an error.
*
****************************************************************************/
#ifdef CONFIG_CANCELLATION_POINTS
void nxsig_wait_irq(FAR struct tcb_s *wtcb, int errcode)
{
#ifdef CONFIG_SMP
irqstate_t flags;
/* We must be in a critical section in order to call up_switch_context()
* below. If we are running on a single CPU architecture, then we know
* interrupts a disabled an there is no need to explicitly call
* enter_critical_section(). However, in the SMP case,
* enter_critical_section() does much more than just disable interrupts on
* the local CPU; it also manages spinlocks to assure the stability of the
* TCB that we are manipulating.
*/
flags = enter_critical_section();
#endif
/* There may be a race condition -- make sure the task is
* still waiting for a signal
*/
if (wtcb->task_state == TSTATE_WAIT_SIG)
{
FAR struct tcb_s *rtcb = this_task();
wtcb->sigunbinfo.si_signo = SIG_CANCEL_TIMEOUT;
wtcb->sigunbinfo.si_code = SI_USER;
wtcb->sigunbinfo.si_errno = errcode;
wtcb->sigunbinfo.si_value.sival_int = 0;
#ifdef CONFIG_SCHED_HAVE_PARENT
wtcb->sigunbinfo.si_pid = 0; /* Not applicable */
wtcb->sigunbinfo.si_status = OK;
#endif
/* Remove the task from waitting list */
dq_rem((FAR dq_entry_t *)wtcb, &g_waitingforsignal);
/* Add the task to ready-to-run task list, and
* perform the context switch if one is needed
*/
if (nxsched_add_readytorun(wtcb))
{
up_switch_context(wtcb, rtcb);
}
}
#ifdef CONFIG_SMP
leave_critical_section(flags);
#endif
}
#endif /* CONFIG_CANCELLATION_POINTS */
/****************************************************************************
* Name: nxsig_timedwait
*
* 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 stored in the
* si_code member. The content of si_value is only meaningful if the
* signal was generated by sigqueue() (or nxsig_queue).
*
* This is an internal OS interface. It is functionally equivalent to
* sigtimedwait() except that:
*
* - It is not a cancellation point, and
* - It does not modify the errno value.
*
* Input Parameters:
* set - The pending signal set.
* info - The returned value (may be NULL).
* timeout - The amount of time to wait (may be NULL)
*
* Returned Value:
* This is an internal OS interface and should not be used by applications.
* It follows the NuttX internal error return policy: Zero (OK) is
* returned on success. A negated errno value is returned on failure.
*
* EAGAIN - No signal specified by set was generated within the specified
* timeout period.
* EINTR - The wait was interrupted by an unblocked, caught signal.
*
****************************************************************************/
int nxsig_timedwait(FAR const sigset_t *set, FAR struct siginfo *info,
FAR const struct timespec *timeout)
{
FAR struct tcb_s *rtcb = this_task();
sigset_t intersection;
FAR sigpendq_t *sigpend;
irqstate_t flags;
sclock_t waitticks;
bool switch_needed;
int ret;
DEBUGASSERT(set != NULL);
/* 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();
/* Check if there is a pending signal corresponding to one of the
* signals in the pending signal set argument.
*/
intersection = nxsig_pendingset(rtcb);
sigandset(&intersection, &intersection, set);
if (!sigisemptyset(&intersection))
{
/* 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 = nxsig_remove_pendingsignal(rtcb,
nxsig_lowest(&intersection));
DEBUGASSERT(sigpend);
/* Return the signal info to the caller if so requested */
if (info != NULL)
{
memcpy(info, &sigpend->info, sizeof(struct siginfo));
}
/* The return value is the number of the signal that awakened us */
ret = sigpend->info.si_signo;
/* Then dispose of the pending signal structure properly */
nxsig_release_pendingsignal(sigpend);
leave_critical_section(flags);
}
/* We will have to wait for a signal to be posted to this task. */
else
{
#ifdef CONFIG_CANCELLATION_POINTS
/* nxsig_timedwait() is not a cancellation point, but it may be called
* from a cancellation point. So if a cancellation is pending, we
* must exit immediately without waiting.
*/
if (check_cancellation_point())
{
/* If there is a pending cancellation, then do not perform
* the wait. Exit now with ECANCELED.
*/
leave_critical_section(flags);
return -ECANCELED;
}
#endif
/* Check if we should wait for the timeout */
if (timeout != NULL)
{
/* 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_SYSTEM_TIME64
waitticks = ((uint64_t)timeout->tv_sec * NSEC_PER_SEC +
(uint64_t)timeout->tv_nsec + NSEC_PER_TICK - 1) /
NSEC_PER_TICK;
#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
if (waitticks > 0)
{
/* Save the set of pending signals to wait for */
rtcb->sigwaitmask = *set;
/* Start the watchdog */
wd_start(&rtcb->waitdog, waitticks,
nxsig_timeout, (uintptr_t)rtcb);
/* Now wait for either the signal or the watchdog, but
* first, make sure this is not the idle task,
* descheduling that isn't going to end well.
*/
DEBUGASSERT(!is_idle_task(rtcb));
/* Remove the tcb task from the ready-to-run list. */
switch_needed = nxsched_remove_readytorun(rtcb, true);
/* Add the task to the specified blocked task list */
rtcb->task_state = TSTATE_WAIT_SIG;
dq_addlast((FAR dq_entry_t *)rtcb, &g_waitingforsignal);
/* Now, perform the context switch if one is needed */
if (switch_needed)
{
up_switch_context(this_task(), rtcb);
}
/* We no longer need the watchdog */
wd_cancel(&rtcb->waitdog);
}
else
{
leave_critical_section(flags);
return -EAGAIN;
}
}
/* No timeout, just wait */
else
{
/* Save the set of pending signals to wait for */
rtcb->sigwaitmask = *set;
/* And wait until one of the unblocked signals is posted,
* but first make sure this is not the idle task,
* descheduling that isn't going to end well.
*/
DEBUGASSERT(!is_idle_task(rtcb));
/* Remove the tcb task from the ready-to-run list. */
switch_needed = nxsched_remove_readytorun(rtcb, true);
/* Add the task to the specified blocked task list */
rtcb->task_state = TSTATE_WAIT_SIG;
dq_addlast((FAR dq_entry_t *)rtcb, &g_waitingforsignal);
/* Now, perform the context switch if one is needed */
if (switch_needed)
{
up_switch_context(this_task(), rtcb);
}
}
/* We are running again, clear the sigwaitmask */
sigemptyset(&rtcb->sigwaitmask);
/* 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 (nxsig_ismember(set, rtcb->sigunbinfo.si_signo))
{
/* Return the signal info to the caller if so requested */
if (info != NULL)
{
memcpy(info, &rtcb->sigunbinfo, sizeof(struct siginfo));
}
/* Yes.. the return value is the number of the signal that
* awakened us.
*/
ret = rtcb->sigunbinfo.si_signo;
}
else
{
/* No... then report the EINTR error */
ret = -EINTR;
}
}
else
{
/* Otherwise, we must have been awakened by the timeout or,
* perhaps, the wait was cancelled.
*/
#ifdef CONFIG_CANCELLATION_POINTS
if (rtcb->sigunbinfo.si_signo == SIG_CANCEL_TIMEOUT)
{
/* The wait was canceled */
ret = -rtcb->sigunbinfo.si_errno;
DEBUGASSERT(ret < 0);
}
else
#endif
{
/* We were awakened by a timeout. Set EAGAIN and return an
* error.
*/
DEBUGASSERT(rtcb->sigunbinfo.si_signo == SIG_WAIT_TIMEOUT);
ret = -EAGAIN;
}
}
leave_critical_section(flags);
}
return ret;
}
/****************************************************************************
* 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 stored in 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.
*
* Input Parameters:
* set - The pending signal set.
* info - The returned value (may be NULL).
* timeout - The amount of time to wait (may be NULL)
*
* Returned 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.
*
****************************************************************************/
int sigtimedwait(FAR const sigset_t *set, FAR struct siginfo *info,
FAR const struct timespec *timeout)
{
int ret;
/* sigtimedwait() is a cancellation point */
enter_cancellation_point();
/* Let nxsig_timedwait() do the work. */
ret = nxsig_timedwait(set, info, timeout);
if (ret < 0)
{
set_errno(-ret);
ret = ERROR;
}
leave_cancellation_point();
return ret;
}