/**************************************************************************** * sched/semaphore/sem_timedwait.c * * Copyright (C) 2011, 2013-2017 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * 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 #include #include #include #include #include #include #include #include #include #include #include #include "sched/sched.h" #include "clock/clock.h" #include "semaphore/semaphore.h" /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: nxsem_timedwait * * Description: * This function will lock the semaphore referenced by sem as in the * sem_wait() function. However, if the semaphore cannot be locked without * waiting for another process or thread to unlock the semaphore by * performing a sem_post() function, this wait will be terminated when the * specified timeout expires. * * The timeout will expire when the absolute time specified by abstime * passes, as measured by the clock on which timeouts are based (that is, * when the value of that clock equals or exceeds abstime), or if the * absolute time specified by abstime has already been passed at the * time of the call. * * This is an internal OS interface. It is functionally equivalent to * sem_wait except that: * * - It is not a cancellation point, and * - It does not modify the errno value. * * Input Parameters: * sem - Semaphore object * abstime - The absolute time to wait until a timeout is declared. * * 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. * That may be one of: * * EINVAL The sem argument does not refer to a valid semaphore. Or the * thread would have blocked, and the abstime parameter specified * a nanoseconds field value less than zero or greater than or * equal to 1000 million. * ETIMEDOUT The semaphore could not be locked before the specified timeout * expired. * EDEADLK A deadlock condition was detected. * EINTR A signal interrupted this function. * ****************************************************************************/ int nxsem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime) { FAR struct tcb_s *rtcb = this_task(); irqstate_t flags; sclock_t ticks; int status; int ret = ERROR; DEBUGASSERT(up_interrupt_context() == false && rtcb->waitdog == NULL); /* Verify the input parameters and, in case of an error, set * errno appropriately. */ #ifdef CONFIG_DEBUG_FEATURES if (!abstime || !sem) { return -EINVAL; } #endif /* Create a watchdog. We will not actually need this watchdog * unless the semaphore is unavailable, but we will reserve it up * front before we enter the following critical section. */ rtcb->waitdog = wd_create(); if (!rtcb->waitdog) { return -ENOMEM; } /* We will disable interrupts until we have completed the semaphore * wait. We need to do this (as opposed to just disabling pre-emption) * because there could be interrupt handlers that are asynchronously * posting semaphores and to prevent race conditions with watchdog * timeout. This is not too bad because interrupts will be re- * enabled while we are blocked waiting for the semaphore. */ flags = enter_critical_section(); /* Try to take the semaphore without waiting. */ ret = nxsem_trywait(sem); if (ret == OK) { /* We got it! */ goto success_with_irqdisabled; } /* We will have to wait for the semaphore. Make sure that we were provided * with a valid timeout. */ if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000) { ret = -EINVAL; goto errout_with_irqdisabled; } /* Convert the timespec to clock ticks. We must have interrupts * disabled here so that this time stays valid until the wait begins. * * clock_abstime2ticks() returns zero on success or a POSITIVE errno * value on failure. */ status = clock_abstime2ticks(CLOCK_REALTIME, abstime, &ticks); /* If the time has already expired return immediately. */ if (status == OK && ticks <= 0) { ret = -ETIMEDOUT; goto errout_with_irqdisabled; } /* Handle any time-related errors */ if (status != OK) { ret = -status; goto errout_with_irqdisabled; } /* Start the watchdog */ (void)wd_start(rtcb->waitdog, ticks, (wdentry_t)nxsem_timeout, 1, getpid()); /* Now perform the blocking wait. If nxsem_wait() fails, the * negated errno value will be returned below. */ ret = nxsem_wait(sem); /* Stop the watchdog timer */ wd_cancel(rtcb->waitdog); /* We can now restore interrupts and delete the watchdog */ success_with_irqdisabled: errout_with_irqdisabled: leave_critical_section(flags); wd_delete(rtcb->waitdog); rtcb->waitdog = NULL; return ret; } /**************************************************************************** * Name: sem_timedwait * * Description: * This function will lock the semaphore referenced by sem as in the * sem_wait() function. However, if the semaphore cannot be locked without * waiting for another process or thread to unlock the semaphore by * performing a sem_post() function, this wait will be terminated when the * specified timeout expires. * * The timeout will expire when the absolute time specified by abstime * passes, as measured by the clock on which timeouts are based (that is, * when the value of that clock equals or exceeds abstime), or if the * absolute time specified by abstime has already been passed at the * time of the call. * * Input Parameters: * sem - Semaphore object * abstime - The absolute time to wait until a timeout is declared. * * Returned Value: * Zero (OK) is returned on success. On failure, -1 (ERROR) is returned * and the errno is set appropriately: * * EINVAL The sem argument does not refer to a valid semaphore. Or the * thread would have blocked, and the abstime parameter specified * a nanoseconds field value less than zero or greater than or * equal to 1000 million. * ETIMEDOUT The semaphore could not be locked before the specified timeout * expired. * EDEADLK A deadlock condition was detected. * EINTR A signal interrupted this function. * ****************************************************************************/ int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime) { int ret; /* sem_timedwait() is a cancellation point */ (void)enter_cancellation_point(); /* Let nxsem_timedout() do the work */ ret = nxsem_timedwait(sem, abstime); if (ret < 0) { set_errno(-ret); ret = ERROR; } leave_cancellation_point(); return ret; }