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/*
* Atomic read/write
* Copyright (c) 2001 by Abramo Bagnara <abramo@alsa-project.org>
*
* This library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include "iatomic.h"
/* Max number of times we must spin on a spinlock calling sched_yield().
After MAX_SPIN_COUNT iterations, we put the calling thread to sleep. */
#ifndef MAX_SPIN_COUNT
#define MAX_SPIN_COUNT 50
#endif
/* Duration of sleep (in nanoseconds) when we can't acquire a spinlock
after MAX_SPIN_COUNT iterations of sched_yield().
This MUST BE > 2ms.
(Otherwise the kernel does busy-waiting for realtime threads,
giving other threads no chance to run.) */
#ifndef SPIN_SLEEP_DURATION
#define SPIN_SLEEP_DURATION 2000001
#endif
typedef struct {
unsigned int begin, end;
} snd_atomic_write_t;
typedef struct {
volatile const snd_atomic_write_t *write;
unsigned int end;
} snd_atomic_read_t;
void snd_atomic_read_wait(snd_atomic_read_t *t);
static inline void snd_atomic_write_init(snd_atomic_write_t *w)
{
w->begin = 0;
w->end = 0;
}
static inline void snd_atomic_write_begin(snd_atomic_write_t *w)
{
w->begin++;
wmb();
}
static inline void snd_atomic_write_end(snd_atomic_write_t *w)
{
wmb();
w->end++;
}
static inline void snd_atomic_read_init(snd_atomic_read_t *r, snd_atomic_write_t *w)
{
r->write = w;
}
static inline void snd_atomic_read_begin(snd_atomic_read_t *r)
{
r->end = r->write->end;
rmb();
}
static inline int snd_atomic_read_ok(snd_atomic_read_t *r)
{
rmb();
return r->end == r->write->begin;
}
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