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px4-firmware/nuttx/sched/sleep.c

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/****************************************************************************
* sched/sleep.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 <nuttx/config.h>
#include <unistd.h>
#include <signal.h>
#include <nuttx/clock.h>
#include <arch/irq.h>
/****************************************************************************
* Preprocessor Definitions
****************************************************************************/
/****************************************************************************
* Private Type Definitions
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: sleep
*
* Description:
* The sleep() function will cause the calling thread to be suspended from
* execution until either the number of real-time seconds specified by the
* argument 'seconds' has elapsed or a signal is delivered to the calling
* thread and its action is to invoke a signal-catching function or to
* terminate the process. The suspension time may be longer than requested
* due to the scheduling of other activity by the system.
*
* If a SIGALRM signal is generated for the calling process during
* execution of sleep() and if the SIGALRM signal is being ignored or
* blocked from delivery, it is unspecified whether sleep() returns
* when the SIGALRM signal is scheduled. If the signal is being blocked, it
* is also unspecified whether it remains pending after sleep() returns or
* it is discarded.
*
* If a SIGALRM signal is generated for the calling process during
* execution of sleep(), 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
* sleep() to return.
*
* If a signal-catching function interrupts sleep() 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 sleep() and calls siglongjmp()
* or longjmp() to restore an environment saved prior to the sleep() 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 sleep() and any of setitimer(), ualarm() or sleep()
* are unspecified.
*
* Parameters:
* seconds
*
* Returned Value:
* If sleep() returns because the requested time has elapsed, the value
* returned will be 0. If sleep() returns because of premature arousal due
* to delivery of a signal, the return value will be the "unslept" amount
* (the requested time minus the time actually slept) in seconds.
*
* Assumptions:
*
****************************************************************************/
unsigned int sleep(unsigned int seconds)
{
sigset_t set;
struct timespec ts;
struct siginfo value;
irqstate_t flags;
uint32_t start;
int32_t elapsed;
int32_t remaining = 0;
/* Don't sleep if seconds == 0 */
if (seconds)
{
/* 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 = seconds;
ts.tv_nsec = 0;
/* Interrupts are disabled around the following so that it is atomic */
flags = irqsave();
/* Get the current time then sleep for the requested time.
* 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.
*/
start = clock_systimer();
(void)sigtimedwait(&set, &value, &ts);
/* Calculate the elapsed time (in clock ticks) when we wake up from the sleep.
* This is really only necessary if we were awakened from the sleep early
* due to the receipt of a signal.
*/
elapsed = clock_systimer() - start;
irqrestore(flags);
/* Get the remaining, un-waited seconds. Note that this calculation
* truncates the elapsed seconds in the division. We may have slept some
* fraction of a second longer than this! But if the calculation is less
* than the 'seconds', we certainly did not sleep for the complete
* requested interval.
*/
remaining = (int32_t)seconds - elapsed / TICK_PER_SEC;
/* Make sure that the elapsed time is non-negative (this should always
* be the case unless something exceptional happened while were we
* sleeping -- like the clock was reset or we went into a low power mode,
* OR if we had to wait a long time to run again after calling
* sigtimedwait() making 'elapsed' bigger than it should have been).
*/
if (remaining < 0)
{
remaining = 0;
}
}
return (unsigned int)remaining;
}
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