/**************************************************************************** * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #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; }