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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/>.
*/
#include <assert.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <kern/atomic.h>
#include <kern/init.h>
#include <kern/mutex.h>
#include <kern/mutex_types.h>
#include <kern/sleepq.h>
#include <kern/syscnt.h>
#ifdef CONFIG_MUTEX_DEBUG
enum {
MUTEX_PLAIN_SC_WAIT_SUCCESSES,
MUTEX_PLAIN_SC_WAIT_ERRORS,
MUTEX_PLAIN_SC_DOWNGRADES,
MUTEX_PLAIN_SC_ERROR_DOWNGRADES,
MUTEX_PLAIN_NR_SCS
};
static struct syscnt mutex_plain_sc_array[MUTEX_PLAIN_NR_SCS];
static void
mutex_plain_register_sc(unsigned int index, const char *name)
{
assert(index < ARRAY_SIZE(mutex_plain_sc_array));
syscnt_register(&mutex_plain_sc_array[index], name);
}
static void
mutex_plain_setup_debug(void)
{
mutex_plain_register_sc(MUTEX_PLAIN_SC_WAIT_SUCCESSES,
"mutex_plain_wait_successes");
mutex_plain_register_sc(MUTEX_PLAIN_SC_WAIT_ERRORS,
"mutex_plain_wait_errors");
mutex_plain_register_sc(MUTEX_PLAIN_SC_DOWNGRADES,
"mutex_plain_downgrades");
mutex_plain_register_sc(MUTEX_PLAIN_SC_ERROR_DOWNGRADES,
"mutex_plain_error_downgrades");
}
static void
mutex_plain_inc_sc(unsigned int index)
{
assert(index < ARRAY_SIZE(mutex_plain_sc_array));
syscnt_inc(&mutex_plain_sc_array[index]);
}
#else /* CONFIG_MUTEX_DEBUG */
#define mutex_plain_setup_debug()
#define mutex_plain_inc_sc(x)
#endif /* CONFIG_MUTEX_DEBUG */
static int
mutex_plain_lock_slow_common(struct mutex *mutex, bool timed, uint64_t ticks)
{
unsigned int state;
struct sleepq *sleepq;
unsigned long flags;
int error;
error = 0;
sleepq = sleepq_lend(mutex, false, &flags);
for (;;) {
state = atomic_swap(&mutex->state, MUTEX_CONTENDED, ATOMIC_RELEASE);
if (state == MUTEX_UNLOCKED) {
break;
}
if (!timed) {
sleepq_wait(sleepq, "mutex");
} else {
error = sleepq_timedwait(sleepq, "mutex", ticks);
if (error) {
break;
}
}
}
if (error) {
mutex_plain_inc_sc(MUTEX_PLAIN_SC_WAIT_ERRORS);
if (sleepq_empty(sleepq)) {
mutex_plain_inc_sc(MUTEX_PLAIN_SC_ERROR_DOWNGRADES);
atomic_cas(&mutex->state, MUTEX_CONTENDED,
MUTEX_LOCKED, ATOMIC_RELAXED);
}
goto out;
}
mutex_plain_inc_sc(MUTEX_PLAIN_SC_WAIT_SUCCESSES);
if (sleepq_empty(sleepq)) {
mutex_plain_inc_sc(MUTEX_PLAIN_SC_DOWNGRADES);
atomic_store(&mutex->state, MUTEX_LOCKED, ATOMIC_RELAXED);
}
out:
sleepq_return(sleepq, flags);
return error;
}
void
mutex_plain_lock_slow(struct mutex *mutex)
{
int error;
error = mutex_plain_lock_slow_common(mutex, false, 0);
assert(!error);
}
int
mutex_plain_timedlock_slow(struct mutex *mutex, uint64_t ticks)
{
return mutex_plain_lock_slow_common(mutex, true, ticks);
}
void
mutex_plain_unlock_slow(struct mutex *mutex)
{
struct sleepq *sleepq;
unsigned long flags;
sleepq = sleepq_acquire(mutex, false, &flags);
if (sleepq == NULL) {
return;
}
sleepq_signal(sleepq);
sleepq_release(sleepq, flags);
}
static int
mutex_plain_bootstrap(void)
{
return 0;
}
INIT_OP_DEFINE(mutex_plain_bootstrap);
static int
mutex_plain_setup(void)
{
mutex_plain_setup_debug();
return 0;
}
#ifdef CONFIG_MUTEX_DEBUG
#define MUTEX_PLAIN_DEBUG_INIT_OP_DEPS \
INIT_OP_DEP(syscnt_setup, true),
#else /* CONFIG_MUTEX_DEBUG */
#define MUTEX_PLAIN_DEBUG_INIT_OP_DEPS
#endif /* CONFIG_MUTEX_DEBUG */
INIT_OP_DEFINE(mutex_plain_setup,
INIT_OP_DEP(mutex_plain_bootstrap, true),
MUTEX_PLAIN_DEBUG_INIT_OP_DEPS
);
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