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/*
* Copyright (c) 2017 Agustina Arzille.
*
* 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_ADAPTIVE_I_H
#define KERN_MUTEX_ADAPTIVE_I_H
#ifndef KERN_MUTEX_H
#error "don't include <kern/mutex/mutex_adaptive_i.h> directly," \
" use <kern/mutex.h> instead"
#endif
#include <assert.h>
#include <errno.h>
#include <stdint.h>
#include <kern/atomic.h>
#include <kern/init.h>
#include <kern/macros.h>
#include <kern/mutex_types.h>
#include <kern/thread.h>
/*
* Mutex flags.
*
* The "contended" flag indicates that threads are waiting for the mutex
* to be unlocked, potentially spinning on the owner. It forces threads
* trying to lock the mutex as well as the owner to take the slow path.
*/
#define MUTEX_ADAPTIVE_CONTENDED 0x1
static inline void
mutex_adaptive_init(struct mutex *mutex)
{
mutex->owner = 0;
}
#define mutex_adaptive_assert_locked(mutex) assert((mutex)->owner != 0)
static inline int
mutex_adaptive_lock_fast(struct mutex *mutex)
{
uintptr_t owner;
owner = atomic_cas(&mutex->owner, 0,
(uintptr_t)thread_self(), ATOMIC_ACQUIRE);
if (unlikely(owner != 0)) {
return EBUSY;
}
return 0;
}
static inline int
mutex_adaptive_unlock_fast(struct mutex *mutex)
{
uintptr_t owner;
owner = atomic_cas(&mutex->owner, (uintptr_t)thread_self(),
0, ATOMIC_RELEASE);
if (unlikely(owner & MUTEX_ADAPTIVE_CONTENDED)) {
return EBUSY;
}
return 0;
}
void mutex_adaptive_lock_slow(struct mutex *mutex);
int mutex_adaptive_timedlock_slow(struct mutex *mutex, uint64_t ticks);
void mutex_adaptive_unlock_slow(struct mutex *mutex);
/*
* Interface exported to the public mutex header.
*/
#define mutex_impl_init mutex_adaptive_init
#define mutex_impl_assert_locked mutex_adaptive_assert_locked
static inline int
mutex_impl_trylock(struct mutex *mutex)
{
return mutex_adaptive_lock_fast(mutex);
}
static inline void
mutex_impl_lock(struct mutex *mutex)
{
int error;
error = mutex_adaptive_lock_fast(mutex);
if (unlikely(error)) {
mutex_adaptive_lock_slow(mutex);
}
}
static inline int
mutex_impl_timedlock(struct mutex *mutex, uint64_t ticks)
{
int error;
error = mutex_adaptive_lock_fast(mutex);
if (unlikely(error)) {
error = mutex_adaptive_timedlock_slow(mutex, ticks);
}
return error;
}
static inline void
mutex_impl_unlock(struct mutex *mutex)
{
int error;
error = mutex_adaptive_unlock_fast(mutex);
if (unlikely(error)) {
mutex_adaptive_unlock_slow(mutex);
}
}
/*
* Mutex init operations. See kern/mutex.h.
*/
#define mutex_impl_bootstrap mutex_adaptive_bootstrap
INIT_OP_DECLARE(mutex_adaptive_bootstrap);
#define mutex_impl_setup mutex_adaptive_setup
INIT_OP_DECLARE(mutex_adaptive_setup);
#endif /* KERN_MUTEX_ADAPTIVE_I_H */
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