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Merge pull request #1002 from rousselk/fix-hwtimer-spin-wait

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Enhance implementation of hwtimer_spin()
This commit is contained in:
Oleg Hahm 2014-04-30 17:42:34 +02:00
commit d206345e0d
1 changed files with 12 additions and 18 deletions
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30
core/hwtimer.c
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@ -1,5 +1,5 @@
/*
* Copyright (C) 2013 Freie Universität Berlin
* Copyright (C) 2014 Freie Universität Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser General
* Public License. See the file LICENSE in the top level directory for more
@ -17,6 +17,7 @@
* @author Thomas Hillebrandt <hillebra@inf.fu-berlin.de>
* @author Kaspar Schleiser <kaspar@schleiser.de>
* @author Oliver Hahm <oliver.hahm@fu-berlin.de>
* @author Kévin Roussel <Kevin.Roussel@inria.fr>
*
* @}
*/
@ -63,28 +64,21 @@ static void hwtimer_releasemutex(void* mutex) {
void hwtimer_spin(unsigned long ticks)
{
DEBUG("hwtimer_spin ticks=%lu\n", ticks);
unsigned long t = hwtimer_arch_now();
/**
* If hwtimer_arch_now + ticks results in an overflow,
unsigned long start = hwtimer_arch_now();
/* compute destination time, possibly resulting in an overflow */
unsigned long stop = start + ticks;
/*
* If there is an overflow (that is: stop time is inferior to start),
* hwtimer_arch_now needs to spin until it has overflowed as well.
*
* If the destination time will result in an overflow, the result
* is smaller than ticks by at least one.
*/
if (t + ticks < ticks) {
while (hwtimer_arch_now() > t);
if (stop < start) {
while (hwtimer_arch_now() > start) /* do nothing */;
}
/**
* set t to destination time, possibly overflowing it
*/
t += ticks;
/**
* wait until the present has past destination time t
*/
while (hwtimer_arch_now() < t);
/* wait until we have passed destination (stop) time */
while (hwtimer_arch_now() < stop) /* do nothing again */;
}
/*---------------------------------------------------------------------------*/