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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_MUTEX_PLAIN_I_H
#define _KERN_MUTEX_PLAIN_I_H
#ifndef _KERN_MUTEX_H
#error "don't include <kern/mutex/mutex_plain_i.h> directly," \
" use <kern/mutex.h> instead"
#endif
#include <assert.h>
#include <kern/atomic.h>
#include <kern/error.h>
#include <kern/mutex_types.h>
#define MUTEX_UNLOCKED 0
#define MUTEX_LOCKED 1
#define MUTEX_CONTENDED 2
static inline void
mutex_plain_init(struct mutex *mutex)
{
mutex->state = MUTEX_UNLOCKED;
}
#define mutex_plain_assert_locked(mutex) \
assert((mutex)->state != MUTEX_UNLOCKED)
static inline int
mutex_plain_lock_fast(struct mutex *mutex)
{
unsigned int state;
state = atomic_cas_acquire(&mutex->state, MUTEX_UNLOCKED, MUTEX_LOCKED);
if (unlikely(state != MUTEX_UNLOCKED)) {
return ERROR_BUSY;
}
return 0;
}
static inline int
mutex_plain_unlock_fast(struct mutex *mutex)
{
unsigned int state;
state = atomic_swap_release(&mutex->state, MUTEX_UNLOCKED);
if (unlikely(state == MUTEX_CONTENDED)) {
return ERROR_BUSY;
}
return 0;
}
void mutex_plain_lock_slow(struct mutex *mutex);
void mutex_plain_unlock_slow(struct mutex *mutex);
/*
* Interface exported to the public mutex header.
*/
#define mutex_impl_init mutex_plain_init
#define mutex_impl_assert_locked mutex_plain_assert_locked
static inline int
mutex_impl_trylock(struct mutex *mutex)
{
return mutex_plain_lock_fast(mutex);
}
static inline void
mutex_impl_lock(struct mutex *mutex)
{
int error;
error = mutex_plain_lock_fast(mutex);
if (unlikely(error)) {
mutex_plain_lock_slow(mutex);
}
}
static inline void
mutex_impl_unlock(struct mutex *mutex)
{
int error;
error = mutex_plain_unlock_fast(mutex);
if (unlikely(error)) {
mutex_plain_unlock_slow(mutex);
}
}
#endif /* _KERN_MUTEX_PLAIN_I_H */
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