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author | px4dev <px4@purgatory.org> | 2012-08-04 15:12:36 -0700 |
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committer | px4dev <px4@purgatory.org> | 2012-08-04 15:12:36 -0700 |
commit | 8a365179eafdf3aea98e60ab9f5882b200d4c759 (patch) | |
tree | 4f38d6d4cd80bd0b6e22e2bb534c3f117ce44e56 /nuttx/sched/sem_timedwait.c | |
download | px4-firmware-8a365179eafdf3aea98e60ab9f5882b200d4c759.tar.gz px4-firmware-8a365179eafdf3aea98e60ab9f5882b200d4c759.tar.bz2 px4-firmware-8a365179eafdf3aea98e60ab9f5882b200d4c759.zip |
Fresh import of the PX4 firmware sources.
Diffstat (limited to 'nuttx/sched/sem_timedwait.c')
-rw-r--r-- | nuttx/sched/sem_timedwait.c | 286 |
1 files changed, 286 insertions, 0 deletions
diff --git a/nuttx/sched/sem_timedwait.c b/nuttx/sched/sem_timedwait.c new file mode 100644 index 000000000..6a4724406 --- /dev/null +++ b/nuttx/sched/sem_timedwait.c @@ -0,0 +1,286 @@ +/**************************************************************************** + * sched/sem_timedwait.c + * + * Copyright (C) 2011 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <gnutt@nuttx.org> + * + * 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 <nuttx/config.h> + +#include <stdint.h> +#include <unistd.h> +#include <semaphore.h> +#include <time.h> +#include <errno.h> +#include <wdog.h> +#include <debug.h> + +#include <nuttx/arch.h> + +#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 _TCB *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) +{ + WDOG_ID wdog; + irqstate_t flags; + int ticks; + int err; + int ret = ERROR; + + DEBUGASSERT(up_interrupt_context() == false); + + /* 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. + */ + + wdog = wd_create(); + if (!wdog) + { + 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(wdog); + 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(wdog, ticks, (wdentry_t)sem_timeout, 1, getpid()); + + /* Now perform the blocking wait */ + + ret = sem_wait(sem); + + /* Stop the watchdog timer */ + + wd_cancel(wdog); + + /* We can now restore interrupts and delete the watchdog */ + + irqrestore(flags); + wd_delete(wdog); + + /* 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(wdog); +errout: + set_errno(err); + return ERROR; +} |