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/*
* Copyright (c) 2017-2019 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/>.
*/
#include <assert.h>
#include <errno.h>
#include <stdbool.h>
#include <stdint.h>
#include <kern/semaphore.h>
#include <kern/semaphore_i.h>
#include <kern/sleepq.h>
void
semaphore_init(struct semaphore *semaphore, uint16_t value, uint16_t max_value)
{
assert(value <= max_value);
semaphore->value = value;
semaphore->max_value = max_value;
}
int
semaphore_trywait(struct semaphore *semaphore)
{
struct sleepq *sleepq;
unsigned long flags;
int error;
sleepq = sleepq_lend_intr_save(semaphore, false, &flags);
if (semaphore->value == 0) {
error = EAGAIN;
} else {
semaphore->value--;
error = 0;
}
sleepq_return_intr_restore(sleepq, flags);
return error;
}
void
semaphore_wait(struct semaphore *semaphore)
{
struct sleepq *sleepq;
unsigned long flags;
sleepq = sleepq_lend_intr_save(semaphore, false, &flags);
for (;;) {
if (semaphore->value != 0) {
semaphore->value--;
break;
}
sleepq_wait(sleepq, "sem");
}
sleepq_return_intr_restore(sleepq, flags);
}
int
semaphore_timedwait(struct semaphore *semaphore, uint64_t ticks)
{
struct sleepq *sleepq;
unsigned long flags;
int error;
sleepq = sleepq_lend_intr_save(semaphore, false, &flags);
for (;;) {
if (semaphore->value != 0) {
semaphore->value--;
error = 0;
break;
}
error = sleepq_timedwait(sleepq, "sem", ticks);
if (error) {
break;
}
}
sleepq_return_intr_restore(sleepq, flags);
return error;
}
int
semaphore_post(struct semaphore *semaphore)
{
struct sleepq *sleepq;
unsigned long flags;
int error;
sleepq = sleepq_lend_intr_save(semaphore, false, &flags);
if (semaphore->value == semaphore->max_value) {
error = EOVERFLOW;
} else {
assert(semaphore->value < semaphore->max_value);
semaphore->value++;
sleepq_signal(sleepq);
error = 0;
}
sleepq_return_intr_restore(sleepq, flags);
return error;
}
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