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168 lines
6.9 KiB
168 lines
6.9 KiB
/**************************************************************************** |
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* sched/usleep.c |
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* |
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* Copyright (C) 2007, 2009, 2012 Gregory Nutt. All rights reserved. |
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* Author: Gregory Nutt <gnutt@nuttx.org> |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in |
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* the documentation and/or other materials provided with the |
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* distribution. |
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* 3. Neither the name NuttX nor the names of its contributors may be |
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* used to endorse or promote products derived from this software |
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* without specific prior written permission. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS |
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED |
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
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* POSSIBILITY OF SUCH DAMAGE. |
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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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/**************************************************************************** |
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* Definitions |
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****************************************************************************/ |
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/**************************************************************************** |
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* Private Type Declarations |
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****************************************************************************/ |
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/**************************************************************************** |
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* Global Variables |
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****************************************************************************/ |
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/**************************************************************************** |
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* Private Variables |
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****************************************************************************/ |
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/**************************************************************************** |
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* Private Function Prototypes |
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****************************************************************************/ |
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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 changes |
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* either the time a SIGALRM is scheduled to be generated, the action |
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* associated with the SIGALRM signal, or whether the SIGALRM signal is |
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* 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 values. |
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* For each interval timer, if the requested timer value requires a finer |
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* granularity than the implementation supports, the actual timer value will |
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* 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(), timer_getoverrun(), |
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* timer_gettime(), timer_settime(), ualarm(), sleep() |
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* 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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sigset_t set; |
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struct timespec ts; |
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struct siginfo value; |
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int errval; |
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int ret = 0; |
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if (usec) |
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{ |
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/* Set up for the sleep. Using the empty set means that we are not |
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* waiting for any particular signal. However, any unmasked signal |
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* can still awaken sigtimedwait(). |
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*/ |
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(void)sigemptyset(&set); |
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ts.tv_sec = usec / 1000000; |
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ts.tv_nsec = (usec % 1000000) * 1000; |
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/* usleep is a simple application of sigtimedwait. */ |
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ret = sigtimedwait(&set, &value, &ts); |
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/* sigtimedwait() cannot succeed. It should always return error with |
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* either (1) EAGAIN meaning that the timeout occurred, or (2) EINTR |
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* meaning that some other unblocked signal was caught. |
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*/ |
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errval = errno; |
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DEBUGASSERT(ret < 0 && (errval == EAGAIN || errval == EINTR)); |
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if (errval == EAGAIN) |
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{ |
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/* The timeout "error" is the normal, successful result */ |
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ret = 0; |
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} |
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} |
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return ret; |
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}
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