114 lines
4.6 KiB
C
114 lines
4.6 KiB
C
/****************************************************************************
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* libs/libc/unistd/lib_usleep.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <sys/types.h>
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#include <unistd.h>
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#include <signal.h>
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#include <assert.h>
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#include <errno.h>
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#include <nuttx/clock.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: usleep
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*
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* Description:
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* The usleep() function will cause the calling thread to be suspended
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* from execution until either the number of real-time microseconds
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* specified by the argument 'usec' has elapsed or a signal is delivered
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* to the calling thread. The suspension time may be longer than requested
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* due to the scheduling of other activity by the system.
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*
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* The 'usec' argument must be less than 1,000,000. If the value of
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* 'usec' is 0, then the call has no effect.
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*
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* If a SIGALRM signal is generated for the calling process during
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* execution of usleep() and if the SIGALRM signal is being ignored or
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* blocked from delivery, it is unspecified whether usleep() returns
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* when the SIGALRM signal is scheduled. If the signal is being blocked, it
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* is also unspecified whether it remains pending after usleep() returns or
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* it is discarded.
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*
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* If a SIGALRM signal is generated for the calling process during
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* execution of usleep(), except as a result of a prior call to alarm(),
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* and if the SIGALRM signal is not being ignored or blocked from delivery,
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* it is unspecified whether that signal has any effect other than causing
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* usleep() to return.
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*
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* If a signal-catching function interrupts usleep() and examines or
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* changes either the time a SIGALRM is scheduled to be generated, the
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* action associated with the SIGALRM signal, or whether the SIGALRM signal
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* is blocked from delivery, the results are unspecified.
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*
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* If a signal-catching function interrupts usleep() and calls siglongjmp()
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* or longjmp() to restore an environment saved prior to the usleep() call,
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* the action associated with the SIGALRM signal and the time at which a
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* SIGALRM signal is scheduled to be generated are unspecified. It is also
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* unspecified whether the SIGALRM signal is blocked, unless the process'
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* signal mask is restored as part of the environment.
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*
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* Implementations may place limitations on the granularity of timer
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* values. For each interval timer, if the requested timer value requires a
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* finer granularity than the implementation supports, the actual timer
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* value will be rounded up to the next supported value.
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*
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* Interactions between usleep() and any of the following are unspecified:
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*
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* nanosleep(), setitimer(), timer_create(), timer_delete(),
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* timer_getoverrun(), timer_gettime(), timer_settime(), ualarm(), sleep()
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*
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* Input Parameters:
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* usec - the number of microseconds to wait.
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*
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* Returned Value:
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* On successful completion, usleep() returns 0. Otherwise, it returns -1
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* and sets errno to indicate the error.
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*
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* Assumptions:
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*
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****************************************************************************/
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int usleep(useconds_t usec)
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{
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struct timespec rqtp;
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time_t sec;
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int ret = 0;
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if (usec)
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{
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/* Let clock_nanosleep() do all of the work. */
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sec = USEC2SEC(usec);
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rqtp.tv_sec = sec;
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rqtp.tv_nsec = (usec - (sec * USEC_PER_SEC)) * NSEC_PER_USEC;
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ret = clock_nanosleep(CLOCK_REALTIME, 0, &rqtp, NULL);
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}
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return ret;
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}
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