mutex.c
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/*
* Copyright (C) 2015 Kaspar Schleiser <kaspar@schleiser.de>
* 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
* @brief Kernel mutex implementation
*
* @author Kaspar Schleiser <kaspar@schleiser.de>
* @author Joakim Nohlgård <joakim.nohlgard@eistec.se>
*
* @}
*/
#include <stdio.h>
#include <inttypes.h>
#include "mutex.h"
#include "thread.h"
#include "sched.h"
#include "irq.h"
#include "list.h"
#define ENABLE_DEBUG (0)
#include "debug.h"
int _mutex_lock(mutex_t *mutex, int blocking)
{
unsigned irqstate = irq_disable();
DEBUG("PID[%" PRIkernel_pid "]: Mutex in use.\n", sched_active_pid);
if (mutex->queue.next == NULL) {
/* mutex is unlocked. */
mutex->queue.next = MUTEX_LOCKED;
DEBUG("PID[%" PRIkernel_pid "]: mutex_wait early out.\n",
sched_active_pid);
irq_restore(irqstate);
return 1;
}
else if (blocking) {
thread_t *me = (thread_t*)sched_active_thread;
DEBUG("PID[%" PRIkernel_pid "]: Adding node to mutex queue: prio: %"
PRIu32 "\n", sched_active_pid, (uint32_t)me->priority);
sched_set_status(me, STATUS_MUTEX_BLOCKED);
if (mutex->queue.next == MUTEX_LOCKED) {
mutex->queue.next = (list_node_t*)&me->rq_entry;
mutex->queue.next->next = NULL;
}
else {
thread_add_to_list(&mutex->queue, me);
}
irq_restore(irqstate);
thread_yield_higher();
/* We were woken up by scheduler. Waker removed us from queue.
* We have the mutex now. */
return 1;
}
else {
irq_restore(irqstate);
return 0;
}
}
void mutex_unlock(mutex_t *mutex)
{
unsigned irqstate = irq_disable();
DEBUG("mutex_unlock(): queue.next: 0x%08x pid: %" PRIkernel_pid "\n",
(unsigned)mutex->queue.next, sched_active_pid);
if (mutex->queue.next == NULL) {
/* the mutex was not locked */
irq_restore(irqstate);
return;
}
if (mutex->queue.next == MUTEX_LOCKED) {
mutex->queue.next = NULL;
/* the mutex was locked and no thread was waiting for it */
irq_restore(irqstate);
return;
}
list_node_t *next = list_remove_head(&mutex->queue);
thread_t *process = container_of((clist_node_t*)next, thread_t, rq_entry);
DEBUG("mutex_unlock: waking up waiting thread %" PRIkernel_pid "\n",
process->pid);
sched_set_status(process, STATUS_PENDING);
if (!mutex->queue.next) {
mutex->queue.next = MUTEX_LOCKED;
}
uint16_t process_priority = process->priority;
irq_restore(irqstate);
sched_switch(process_priority);
}
void mutex_unlock_and_sleep(mutex_t *mutex)
{
DEBUG("PID[%" PRIkernel_pid "]: unlocking mutex. queue.next: 0x%08x, and "
"taking a nap\n", sched_active_pid, (unsigned)mutex->queue.next);
unsigned irqstate = irq_disable();
if (mutex->queue.next) {
if (mutex->queue.next == MUTEX_LOCKED) {
mutex->queue.next = NULL;
}
else {
list_node_t *next = list_remove_head(&mutex->queue);
thread_t *process = container_of((clist_node_t*)next, thread_t,
rq_entry);
DEBUG("PID[%" PRIkernel_pid "]: waking up waiter.\n", process->pid);
sched_set_status(process, STATUS_PENDING);
if (!mutex->queue.next) {
mutex->queue.next = MUTEX_LOCKED;
}
}
}
DEBUG("PID[%" PRIkernel_pid "]: going to sleep.\n", sched_active_pid);
sched_set_status((thread_t*)sched_active_thread, STATUS_SLEEPING);
irq_restore(irqstate);
thread_yield_higher();
}