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/*
* Copyright (C) 2013 Freie Universität Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup core_sync
* @{
*
* @file mutex.c
* @brief Kernel mutex implementation
*
* @author Kaspar Schleiser <kaspar@schleiser.de>
*
* @}
*/
#include <stdio.h>
#include <inttypes.h>
#include "mutex.h"
#include "tcb.h"
#include "atomic.h"
#include "kernel.h"
#include "sched.h"
#include "thread.h"
#include "irq.h"
#include "thread.h"
#define ENABLE_DEBUG (0)
#include "debug.h"
static void mutex_wait(struct mutex_t *mutex);
int mutex_trylock(struct mutex_t *mutex)
{
DEBUG("%s: trylocking to get mutex. val: %u\n", sched_active_thread->name, mutex->val);
return (atomic_set_return(&mutex->val, 1) == 0);
}
void mutex_lock(struct mutex_t *mutex)
{
DEBUG("%s: trying to get mutex. val: %u\n", sched_active_thread->name, mutex->val);
if (atomic_set_return(&mutex->val, 1) != 0) {
/* mutex was locked. */
mutex_wait(mutex);
}
}
static void mutex_wait(struct mutex_t *mutex)
{
int irqstate = disableIRQ();
DEBUG("%s: Mutex in use. %u\n", sched_active_thread->name, mutex->val);
if (mutex->val == 0) {
/* somebody released the mutex. return. */
mutex->val = 1;
DEBUG("%s: mutex_wait early out. %u\n", sched_active_thread->name, mutex->val);
restoreIRQ(irqstate);
return;
}
sched_set_status((tcb_t*) sched_active_thread, STATUS_MUTEX_BLOCKED);
queue_node_t n;
n.priority = (unsigned int) sched_active_thread->priority;
n.data = (unsigned int) sched_active_thread;
n.next = NULL;
DEBUG("%s: Adding node to mutex queue: prio: %" PRIu32 "\n", sched_active_thread->name, n.priority);
queue_priority_add(&(mutex->queue), &n);
restoreIRQ(irqstate);
thread_yield();
/* we were woken up by scheduler. waker removed us from queue. we have the mutex now. */
}
void mutex_unlock(struct mutex_t *mutex)
{
DEBUG("%s: unlocking mutex. val: %u pid: %u\n", sched_active_thread->name, mutex->val, sched_active_pid);
int irqstate = disableIRQ();
if (mutex->val != 0) {
queue_node_t *next = queue_remove_head(&(mutex->queue));
if (next) {
tcb_t *process = (tcb_t *) next->data;
DEBUG("%s: waking up waiter.\n", process->name);
sched_set_status(process, STATUS_PENDING);
sched_switch(process->priority);
}
else {
mutex->val = 0;
}
}
restoreIRQ(irqstate);
}
void mutex_unlock_and_sleep(struct mutex_t *mutex)
{
DEBUG("%s: unlocking mutex. val: %u pid: %u, and taking a nap\n", sched_active_thread->name, mutex->val, sched_active_pid);
int irqstate = disableIRQ();
if (mutex->val != 0) {
queue_node_t *next = queue_remove_head(&(mutex->queue));
if (next) {
tcb_t *process = (tcb_t *) next->data;
DEBUG("%s: waking up waiter.\n", process->name);
sched_set_status(process, STATUS_PENDING);
}
else {
mutex->val = 0;
}
}
DEBUG("%s: going to sleep.\n", sched_active_thread->name);
sched_set_status((tcb_t*) sched_active_thread, STATUS_SLEEPING);
restoreIRQ(irqstate);
thread_yield();
}