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incubator-nuttx/sched/signal/sig_timedwait.c

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/****************************************************************************
* sched/signal/sig_timedwait.c
*
* SPDX-License-Identifier: Apache-2.0
*
* 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();
if (wtcb->sigunbinfo != NULL)
{
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, list_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();
if (wtcb->sigunbinfo != NULL)
{
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, list_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_clockwait
*
* 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:
* clockid - The ID of the clock to be used to measure the timeout.
* flags - Open flags. TIMER_ABSTIME is the only supported flag.
* rqtp - The amount of time to be suspended from execution.
* rmtp - If the rmtp argument is non-NULL, the timespec structure
* referenced by it is updated to contain the amount of time
* remaining in the interval (the requested time minus the time
* actually slept)
*
* Returned Value:
* This is an internal OS interface and should not be used by applications.
* A negated errno value is returned on failure.
*
* EAGAIN - wait time is zero.
* EINTR - The wait was interrupted by an unblocked, caught signal.
*
* Notes:
* This function should be called with critical section set.
*
****************************************************************************/
int nxsig_clockwait(int clockid, int flags,
FAR const struct timespec *rqtp,
FAR struct timespec *rmtp)
{
FAR struct tcb_s *rtcb = this_task();
irqstate_t iflags;
clock_t expect = 0;
clock_t stop;
if (rqtp && (rqtp->tv_nsec < 0 || rqtp->tv_nsec >= 1000000000))
{
return -EINVAL;
}
/* If rqtp is zero, yield CPU and return
* Notice: The behavior of sleep(0) is not defined in POSIX, so there are
* different implementations:
* 1. In Linux, nanosleep(0) will call schedule() to yield CPU:
* https://elixir.bootlin.com/linux/latest/source/kernel/time/
* hrtimer.c#L2038
* 2. In BSD, nanosleep(0) will return immediately:
* https://github.com/freebsd/freebsd-src/blob/
* 475fa89800086718bd9249fd4dc3f862549f1f78/crypto/openssh/
* openbsd-compat/bsd-misc.c#L243
*/
if (rqtp && rqtp->tv_sec == 0 && rqtp->tv_nsec == 0)
{
sched_yield();
return -EAGAIN;
}
#ifdef CONFIG_CANCELLATION_POINTS
/* nxsig_clockwait() 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.
*/
return -ECANCELED;
}
#endif
iflags = enter_critical_section();
if (rqtp)
{
/* Start the watchdog timer */
if ((flags & TIMER_ABSTIME) == 0)
{
expect = clock_systime_ticks() + clock_time2ticks(rqtp);
wd_start_abstick(&rtcb->waitdog, expect,
nxsig_timeout, (uintptr_t)rtcb);
}
else if (clockid == CLOCK_REALTIME)
{
wd_start_realtime(&rtcb->waitdog, rqtp,
nxsig_timeout, (uintptr_t)rtcb);
}
else
{
wd_start_abstime(&rtcb->waitdog, rqtp,
nxsig_timeout, (uintptr_t)rtcb);
}
}
/* Remove the tcb task from the ready-to-run list. */
nxsched_remove_self(rtcb);
/* 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 */
up_switch_context(this_task(), rtcb);
/* We no longer need the watchdog */
if (rqtp)
{
wd_cancel(&rtcb->waitdog);
stop = clock_systime_ticks();
}
leave_critical_section(iflags);
if (rqtp && rmtp && expect)
{
clock_ticks2time(rmtp, expect > stop ? expect - stop : 0);
}
return 0;
}
/****************************************************************************
* 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;
siginfo_t unbinfo;
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);
}
/* We will have to wait for a signal to be posted to this task. */
else
{
rtcb->sigunbinfo = (info == NULL) ? &unbinfo : info;
/* Save the set of pending signals to wait for */
rtcb->sigwaitmask = *set;
leave_critical_section(flags);
ret = nxsig_clockwait(CLOCK_REALTIME, 0, timeout, NULL);
if (ret < 0)
{
rtcb->sigunbinfo = NULL;
return ret;
}
flags = enter_critical_section();
/* 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))
{
/* 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;
}
}
rtcb->sigunbinfo = NULL;
}
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;
}
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