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/****************************************************************************
* sched/usleep.c
*
* Copyright (C) 2007, 2009, 2012 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 <sys/types.h>
#include <unistd.h>
#include <signal.h>
#include <assert.h>
#include <errno.h>
/****************************************************************************
* Definitions
****************************************************************************/
/****************************************************************************
* Private Type Declarations
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: usleep
*
* Description:
* The usleep() function will cause the calling thread to be suspended
* from execution until either the number of real-time microseconds
* specified by the argument 'usec' has elapsed or a signal is delivered
* to the calling thread. The suspension time may be longer than requested
* due to the scheduling of other activity by the system.
*
* The 'usec' argument must be less than 1,000,000. If the value of
* 'usec' is 0, then the call has no effect.
*
* If a SIGALRM signal is generated for the calling process during
* execution of usleep() and if the SIGALRM signal is being ignored or
* blocked from delivery, it is unspecified whether usleep() returns
* when the SIGALRM signal is scheduled. If the signal is being blocked, it
* is also unspecified whether it remains pending after usleep() returns or
* it is discarded.
*
* If a SIGALRM signal is generated for the calling process during
* execution of usleep(), except as a result of a prior call to alarm(),
* and if the SIGALRM signal is not being ignored or blocked from delivery,
* it is unspecified whether that signal has any effect other than causing
* usleep() to return.
*
* If a signal-catching function interrupts usleep() and examines or changes
* either the time a SIGALRM is scheduled to be generated, the action
* associated with the SIGALRM signal, or whether the SIGALRM signal is
* blocked from delivery, the results are unspecified.
*
* If a signal-catching function interrupts usleep() and calls siglongjmp()
* or longjmp() to restore an environment saved prior to the usleep() call,
* the action associated with the SIGALRM signal and the time at which a
* SIGALRM signal is scheduled to be generated are unspecified. It is also
* unspecified whether the SIGALRM signal is blocked, unless the process'
* signal mask is restored as part of the environment.
*
* Implementations may place limitations on the granularity of timer values.
* For each interval timer, if the requested timer value requires a finer
* granularity than the implementation supports, the actual timer value will
* be rounded up to the next supported value.
*
* Interactions between usleep() and any of the following are unspecified:
*
* nanosleep(), setitimer(), timer_create(), timer_delete(), timer_getoverrun(),
* timer_gettime(), timer_settime(), ualarm(), sleep()
* Parameters:
* usec - the number of microseconds to wait.
*
* Returned Value:
* On successful completion, usleep() returns 0. Otherwise, it returns -1
* and sets errno to indicate the error.
*
* Assumptions:
*
****************************************************************************/
int usleep(useconds_t usec)
{
sigset_t set;
struct timespec ts;
struct siginfo value;
int errval;
int ret = 0;
if (usec)
{
/* Set up for the sleep. Using the empty set means that we are not
* waiting for any particular signal. However, any unmasked signal
* can still awaken sigtimedwait().
*/
(void)sigemptyset(&set);
ts.tv_sec = usec / 1000000;
ts.tv_nsec = (usec % 1000000) * 1000;
/* usleep is a simple application of sigtimedwait. */
ret = sigtimedwait(&set, &value, &ts);
/* sigtimedwait() cannot succeed. It should always return error with
* either (1) EAGAIN meaning that the timeout occurred, or (2) EINTR
* meaning that some other unblocked signal was caught.
*/
errval = errno;
DEBUGASSERT(ret < 0 && (errval == EAGAIN || errval == EINTR));
if (errval == EAGAIN)
{
/* The timeout "error" is the normal, successful result */
ret = 0;
}
}
return ret;
}
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