/**************************************************************************** * sched/sem_timedwait.c * * Copyright (C) 2011, 2013 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 "os_internal.h" #include "clock_internal.h" #include "sem_internal.h" /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ /**************************************************************************** * Private Type Declarations ****************************************************************************/ /**************************************************************************** * Global Variables ****************************************************************************/ /**************************************************************************** * Private Variables ****************************************************************************/ /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Name: sem_timeout * * Description: * This function is called if the timeout elapses before the message queue * becomes non-empty. * * Parameters: * argc - the number of arguments (should be 1) * pid - the task ID of the task to wakeup * * Return Value: * None * * Assumptions: * ****************************************************************************/ static void sem_timeout(int argc, uint32_t pid) { FAR struct tcb_s *wtcb; irqstate_t flags; /* Disable interrupts to avoid race conditions */ flags = irqsave(); /* Get the TCB associated with this pid. It is possible that * task may no longer be active when this watchdog goes off. */ wtcb = sched_gettcb((pid_t)pid); /* It is also possible that an interrupt/context switch beat us to the * punch and already changed the task's state. */ if (wtcb && wtcb->task_state == TSTATE_WAIT_SEM) { /* Cancel the semaphore wait */ sem_waitirq(wtcb, ETIMEDOUT); } /* Interrupts may now be enabled. */ irqrestore(flags); } /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * 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. * * Parameters: * sem - Semaphore object * abstime - The absolute time to wait until a timeout is declared. * * Return Value: * One success, the length of the selected message in bytes.is * returned. 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) { FAR struct tcb_s *rtcb = (FAR struct tcb_s *)g_readytorun.head; irqstate_t flags; int ticks; int err; 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 if (!abstime || !sem) { err = EINVAL; goto errout; } #endif /* Create a watchdog. We will not actually need this watchdog * unless the 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) { err = ENOMEM; goto errout; } /* 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 asynchronoulsy * 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 = irqsave(); /* Try to take the semaphore without waiting. */ ret = sem_trywait(sem); if (ret == 0) { /* We got it! */ irqrestore(flags); wd_delete(rtcb->waitdog); rtcb->waitdog = NULL; return OK; } /* We will have to wait for the semphore. Make sure that we were provided * with a valid timeout. */ if (abstime->tv_sec < 0 || abstime->tv_nsec > 1000000000) { err = EINVAL; goto errout_disabled; } /* Convert the timespec to clock ticks. We must have interrupts * disabled here so that this time stays valid until the wait begins. */ err = clock_abstime2ticks(CLOCK_REALTIME, abstime, &ticks); /* If the time has already expired return immediately. */ if (err == OK && ticks <= 0) { err = ETIMEDOUT; goto errout_disabled; } /* Handle any time-related errors */ if (err != OK) { goto errout_disabled; } /* Start the watchdog */ err = OK; wd_start(rtcb->waitdog, ticks, (wdentry_t)sem_timeout, 1, getpid()); /* Now perform the blocking wait */ ret = sem_wait(sem); /* Stop the watchdog timer */ wd_cancel(rtcb->waitdog); /* We can now restore interrupts and delete the watchdog */ irqrestore(flags); wd_delete(rtcb->waitdog); rtcb->waitdog = NULL; /* We are either returning success or an error detected by sem_wait() * or the timeout detected by sem_timeout(). The 'errno' value has * been set appropriately by sem_wait() or sem_timeout() in those * cases. */ return ret; /* Error exits */ errout_disabled: irqrestore(flags); wd_delete(rtcb->waitdog); rtcb->waitdog = NULL; errout: set_errno(err); return ERROR; }