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214 lines
4.0 KiB
C
214 lines
4.0 KiB
C
/* See the end of this file for copyright and license terms. */
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#include <arch/atom.h>
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#include <arch/cpufunc.h>
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#include <gay/clist.h>
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#include <gay/mutex.h>
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#include <gay/sched.h>
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#include <gay/systm.h>
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#include <gay/util.h>
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#if CFG_DEBUG_MTX
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#define MTX_ASSERT(x) KASSERT(x)
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#else
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#define MTX_ASSERT(x) ({})
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#endif
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void spin_init(spin_t *spin)
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{
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atom_init(&spin->lock, 0);
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}
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void spin_lock(spin_t *spin)
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{
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MTX_ASSERT(in_critical());
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spin_loop {
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if (atom_xchg(&spin->lock, 1) == 0)
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break;
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}
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}
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bool spin_trylock(spin_t *spin)
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{
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MTX_ASSERT(in_critical());
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return atom_xchg(&spin->lock, 1) == 0;
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}
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void spin_unlock(spin_t *spin)
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{
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MTX_ASSERT(in_critical());
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atom_init(&spin->lock, 0);
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}
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void mtx_init(struct mtx *mtx)
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{
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atom_init(&mtx->lock, 1);
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spin_init(&mtx->wait_queue_lock);
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clist_init(&mtx->wait_queue);
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}
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void mtx_lock(struct mtx *mtx)
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{
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MTX_ASSERT(!in_critical());
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critical_enter();
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/*
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* When the mutex is locked, its lock value goes to 0.
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* atom_dec() returns true if the value *after* the decrement is
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* nonzero, meaning the lock value has become negative.
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*/
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if (atom_dec(&mtx->lock)) {
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struct task *this_task = current;
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struct lock_waiter waiter = {
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.task = this_task,
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};
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spin_lock(&mtx->wait_queue_lock);
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if (atom_cmp_xchg(&mtx->lock, 1, 0) == 1) {
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/* mutex was unlocked after we failed to claim it, but
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* before the other thread claimed wait_queue_lock */
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spin_unlock(&mtx->wait_queue_lock);
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critical_leave();
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} else {
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this_task->state = TASK_BLOCKED;
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clist_add(&mtx->wait_queue, &waiter.clink);
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spin_unlock(&mtx->wait_queue_lock);
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critical_leave();
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schedule();
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}
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} else {
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critical_leave();
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}
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}
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bool mtx_trylock(struct mtx *mtx)
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{
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MTX_ASSERT(!in_critical());
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return atom_cmp_xchg(&mtx->lock, 1, 0) == 1;
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}
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void mtx_unlock(struct mtx *mtx)
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{
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MTX_ASSERT(!in_critical());
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critical_enter();
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if (atom_add(&mtx->lock, 1) < 0) {
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spin_lock(&mtx->wait_queue_lock);
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if (!clist_is_empty(&mtx->wait_queue)) {
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struct lock_waiter *waiter = clist_del_first_entry(
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&mtx->wait_queue,
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typeof(*waiter),
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clink
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);
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waiter->task->state = TASK_READY;
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}
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spin_unlock(&mtx->wait_queue_lock);
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}
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critical_leave();
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}
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void sem_init(struct sem *sem, int initial_count)
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{
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atom_init(&sem->count, initial_count);
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spin_init(&sem->wait_queue_lock);
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clist_init(&sem->wait_queue);
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}
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int sem_down(struct sem *sem)
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{
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MTX_ASSERT(!in_critical());
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critical_enter();
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int ret = atom_sub(&sem->count, 1);
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if (ret < 0) {
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struct task *this_task = current;
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struct lock_waiter waiter = {
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.task = this_task,
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};
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this_task->state = TASK_BLOCKED;
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spin_lock(&sem->wait_queue_lock);
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clist_add(&sem->wait_queue, &waiter.clink);
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spin_unlock(&sem->wait_queue_lock);
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critical_leave();
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schedule();
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ret = 0;
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} else {
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critical_leave();
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}
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return ret;
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}
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int sem_up(struct sem *sem)
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{
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MTX_ASSERT(!in_critical());
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critical_enter();
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int ret = atom_add(&sem->count, 1);
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if (ret <= 0) {
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spin_lock(&sem->wait_queue_lock);
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if (!clist_is_empty(&sem->wait_queue)) {
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struct lock_waiter *waiter = clist_del_first_entry(
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&sem->wait_queue,
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typeof(*waiter),
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clink
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);
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waiter->task->state = TASK_READY;
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}
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spin_unlock(&sem->wait_queue_lock);
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ret = 0;
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}
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critical_leave();
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return ret;
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}
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int sem_trydown(struct sem *sem)
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{
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MTX_ASSERT(!in_critical());
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critical_enter();
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int ret = atom_sub(&sem->count, 1);
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if (ret < 0) {
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atom_inc(&sem->count);
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ret = -1;
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}
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critical_leave();
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return ret;
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}
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/*
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* This file is part of GayBSD.
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* Copyright (c) 2021 fef <owo@fef.moe>.
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*
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* GayBSD is nonviolent software: you may only use, redistribute, and/or
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* modify it under the terms of the Cooperative Nonviolent Public License
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* (CNPL) as found in the LICENSE file in the source code root directory
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* or at <https://git.pixie.town/thufie/npl-builder>; either version 7
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* of the license, or (at your option) any later version.
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*
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* GayBSD comes with ABSOLUTELY NO WARRANTY, to the extent
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* permitted by applicable law. See the CNPL for details.
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*/
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