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/*
* Copyright (c) 2017 Richard Braun.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef _KERN_SEMAPHORE_I_H
#define _KERN_SEMAPHORE_I_H
#include <kern/assert.h>
#include <machine/atomic.h>
struct semaphore {
unsigned int value;
};
static inline unsigned int
semaphore_dec(struct semaphore *semaphore)
{
unsigned int prev, value;
do {
value = semaphore->value;
if (value == 0) {
break;
}
prev = atomic_cas_uint(&semaphore->value, value, value - 1);
} while (prev != value);
return value;
}
static inline unsigned int
semaphore_inc(struct semaphore *semaphore)
{
unsigned int prev;
prev = atomic_fetchadd_uint(&semaphore->value, 1);
assert(prev != SEMAPHORE_VALUE_MAX);
return prev;
}
void semaphore_wait_slow(struct semaphore *semaphore);
void semaphore_post_slow(struct semaphore *semaphore);
#endif /* _KERN_SEMAPHORE_I_H */
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