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nuttx/sched/clock_gettime.c
patacongo 81ca27c9b0 Fix some timer race conditions 
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3949 42af7a65-404d-4744-a932-0658087f49c3
2011-09-11 17:48:52 +00:00

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/************************************************************************
* sched/clock_gettime.c
*
* Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* 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 <nuttx/rtc.h>
#include <stdint.h>
#include <time.h>
#include <errno.h>
#include <debug.h>
#include <arch/irq.h>
#include "clock_internal.h"
/************************************************************************
* Definitions
************************************************************************/
/************************************************************************
* Private Type Declarations
************************************************************************/
/************************************************************************
* Private Function Prototypes
************************************************************************/
/**********************************************************************
* Public Constant Data
**********************************************************************/
/************************************************************************
* Public Variables
************************************************************************/
/**********************************************************************
* Private Variables
**********************************************************************/
/************************************************************************
* Private Functions
************************************************************************/
/************************************************************************
* Public Functions
************************************************************************/
/************************************************************************
* Function: clock_gettime
*
* Description:
* Clock Functions based on POSIX APIs
*
************************************************************************/
int clock_gettime(clockid_t clock_id, struct timespec *tp)
{
#ifndef CONFIG_SYSTEM_UTC
uint32_t msecs;
uint32_t secs;
uint32_t nsecs;
#else
uint32_t system_utc;
uint32_t tickcount;
#endif
#if defined(CONFIG_RTC) || defined(CONFIG_SYSTEM_UTC)
irqstate_t flags;
#endif
int ret = OK;
sdbg("clock_id=%d\n", clock_id);
/* CLOCK_REALTIME - POSIX demands this to be present. This is the wall
* time clock.
*/
if (clock_id == CLOCK_REALTIME && tp)
{
#ifndef CONFIG_SYSTEM_UTC
/* Get the elapsed time since power up (in milliseconds) biased
* as appropriate.
*/
msecs = MSEC_PER_TICK * (clock_systimer() - g_tickbias);
sdbg("msecs = %d g_tickbias=%d\n",
(int)msecs, (int)g_tickbias);
/* Get the elapsed time in seconds and nanoseconds. */
secs = msecs / MSEC_PER_SEC;
nsecs = (msecs - (secs * MSEC_PER_SEC)) * NSEC_PER_MSEC;
sdbg("secs = %d + %d nsecs = %d + %d\n",
(int)msecs, (int)g_basetime.tv_sec,
(int)nsecs, (int)g_basetime.tv_nsec);
/* Add the base time to this. */
secs += (uint32_t)g_basetime.tv_sec;
nsecs += (uint32_t)g_basetime.tv_nsec;
/* Handle carry to seconds. */
if (nsecs > NSEC_PER_SEC)
{
uint32_t dwCarrySecs = nsecs / NSEC_PER_SEC;
secs += dwCarrySecs;
nsecs -= (dwCarrySecs * NSEC_PER_SEC);
}
/* And return the result to the caller. */
tp->tv_sec = (time_t)secs;
tp->tv_nsec = (long)nsecs;
#else /* if CONFIG_SYSTEM_UTC=y */
#ifdef CONFIG_RTC
if (g_rtc_enabled)
{
/* up_rtc_gettime() returns the time in seconds and up_rtc_getclock()
* will return the time int RTC clock ticks. Under the hood, these
* are probably based on the same running time. However, since we
* sample this time twice, we have to add the following strange logic
* to assure that the fractional second value does not rollover to
* a full second between sampling times.
*/
clock_t rtc_frac; /* Current fractional seconds in RTC ticks */
clock_t rtc_last; /* Previous fractional seconds in RTC ticks */
time_t rtc_sec; /* Current seconds */
/* Interrupts are disabled here only to prevent interrupts and context
* switches from interfering with the consecutive time samples. I
* expect to go through this loop 1 time 99.9% of the time and then
* only twice on the remaining cornercases.
*/
flags = irqsave();
rtc_frac = up_rtc_getclock() & (RTC_CLOCKS_PER_SEC-1);
do
{
rtc_last = rtc_frac;
rtc_sec = up_rtc_gettime();
rtc_frac = up_rtc_getclock() & (RTC_CLOCKS_PER_SEC-1);
}
while (rtc_frac < rtc_last);
irqrestore(flags);
/* Okay.. the samples should be as close together in time as possible
* and we can be assured that no fractional second rollover occurred
* between the samples.
*/
tp->tv_sec = rtc_sec;
tp->tv_nsec = rtc_frac * (1000000000/RTC_CLOCKS_PER_SEC);
}
else
#endif
{
/* Disable interrupts while g_system_utc and g_tickcount are sampled
* so that we can be assured that g_system_utc and g_tickcount are based
* at the same point in time.
*/
flags = irqsave();
system_utc = g_system_utc;
tickcount = g_tickcount;
irqrestore(flags);
tp->tv_sec = system_utc;
tp->tv_nsec = tickcount * (1000000000/TICK_PER_SEC);
}
#endif
sdbg("Returning tp=(%d,%d)\n",
(int)tp->tv_sec, (int)tp->tv_nsec);
}
/* CLOCK_ACTIVETIME is non-standard. Returns active UTC time, which is
* disabled during power down modes. Unit is 1 second.
*/
#ifdef CONFIG_RTC
else if (clock_id == CLOCK_ACTIVETIME && g_rtc_enabled && tp)
{
/* Disable interrupts while g_system_utc and g_tickcount are sampled
* so that we can be assured that g_system_utc and g_tickcount are based
* at the same point in time.
*/
flags = irqsave();
system_utc = g_system_utc;
tickcount = g_tickcount;
irqrestore(flags);
tp->tv_sec = system_utc;
tp->tv_nsec = tickcount * (1000000000/TICK_PER_SEC);
}
#endif
else
{
sdbg("Returning ERROR\n");
errno = EINVAL;
ret = ERROR;
}
return ret;
}
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