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/*
* Copyright (c) 2013-2014 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_I_H
#define _KERN_MUTEX_I_H
#include <kern/assert.h>
#include <kern/list.h>
#include <kern/spinlock.h>
#include <kern/thread.h>
#include <machine/atomic.h>
#define MUTEX_UNLOCKED 0
#define MUTEX_LOCKED 1
#define MUTEX_CONTENDED 2
struct mutex_waiter {
struct list node;
struct thread *thread;
};
struct mutex {
unsigned int state;
struct spinlock lock;
struct list waiters;
};
void mutex_lock_slow(struct mutex *mutex);
void mutex_unlock_slow(struct mutex *mutex);
static inline unsigned int
mutex_tryacquire(struct mutex *mutex)
{
return atomic_cas_uint(&mutex->state, MUTEX_UNLOCKED, MUTEX_LOCKED);
}
static inline unsigned int
mutex_tryacquire_slow(struct mutex *mutex)
{
return atomic_swap_uint(&mutex->state, MUTEX_CONTENDED);
}
static inline unsigned int
mutex_release(struct mutex *mutex)
{
unsigned int state;
state = atomic_swap_uint(&mutex->state, MUTEX_UNLOCKED);
assert((state == MUTEX_LOCKED) || (state == MUTEX_CONTENDED));
return state;
}
static inline void
mutex_queue(struct mutex *mutex, struct mutex_waiter *waiter)
{
list_insert_tail(&mutex->waiters, &waiter->node);
}
static inline void
mutex_queue_list(struct mutex *mutex, struct list *waiters)
{
list_concat(&mutex->waiters, waiters);
}
static inline void
mutex_wait(struct mutex *mutex, struct mutex_waiter *waiter)
{
unsigned int state;
do {
thread_sleep(&mutex->lock);
state = mutex_tryacquire_slow(mutex);
} while (state != MUTEX_UNLOCKED);
list_remove(&waiter->node);
}
static inline void
mutex_signal(struct mutex *mutex)
{
struct mutex_waiter *waiter;
if (!list_empty(&mutex->waiters)) {
waiter = list_first_entry(&mutex->waiters, struct mutex_waiter, node);
thread_wakeup(waiter->thread);
}
}
static inline void
mutex_trydowngrade(struct mutex *mutex)
{
if (list_empty(&mutex->waiters)) {
unsigned int state;
state = atomic_swap_uint(&mutex->state, MUTEX_LOCKED);
assert(state == MUTEX_CONTENDED);
}
}
#endif /* _KERN_MUTEX_I_H */
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