/*
* Copyright (c) 2001-2004 Jakub Jermar
* Copyright (c) 2023 Jiří Zárevúcky
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* - The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/** @addtogroup kernel_sync
* @{
*/
/**
* @file
* @brief Mutexes.
*/
#include <assert.h>
#include <errno.h>
#include <synch/mutex.h>
#include <synch/semaphore.h>
#include <arch.h>
#include <stacktrace.h>
#include <cpu.h>
#include <proc/thread.h>
/** Initialize mutex.
*
* @param mtx Mutex.
* @param type Type of the mutex.
*/
void mutex_initialize(mutex_t *mtx, mutex_type_t type)
{
mtx->type = type;
mtx->owner = NULL;
mtx->nesting = 0;
semaphore_initialize(&mtx->sem, 1);
}
/** Find out whether the mutex is currently locked.
*
* @param mtx Mutex.
*
* @return True if the mutex is locked, false otherwise.
*/
bool mutex_locked(mutex_t *mtx)
{
errno_t rc = semaphore_trydown(&mtx->sem);
if (rc == EOK) {
semaphore_up(&mtx->sem);
}
return rc != EOK;
}
static void mutex_lock_active(mutex_t *mtx)
{
assert((mtx->type == MUTEX_ACTIVE) || !THREAD);
const unsigned deadlock_treshold = 100000000;
unsigned int cnt = 0;
bool deadlock_reported = false;
while (semaphore_trydown(&mtx->sem) != EOK) {
if (cnt++ > deadlock_treshold) {
printf("cpu%u: looping on active mutex %p\n", CPU->id, mtx);
stack_trace();
cnt = 0;
deadlock_reported = true;
}
}
if (deadlock_reported)
printf("cpu%u: not deadlocked\n", CPU->id);
}
/** Acquire mutex.
*
* This operation is uninterruptible and cannot fail.
*/
void mutex_lock(mutex_t *mtx)
{
if (mtx->type == MUTEX_RECURSIVE && mtx->owner == THREAD) {
assert(THREAD);
mtx->nesting++;
return;
}
if (mtx->type == MUTEX_ACTIVE || !THREAD) {
mutex_lock_active(mtx);
return;
}
semaphore_down(&mtx->sem);
mtx->owner = THREAD;
mtx->nesting = 1;
}
/** Acquire mutex with timeout.
*
* @param mtx Mutex.
* @param usec Timeout in microseconds.
*
* @return EOK if lock was successfully acquired, something else otherwise.
*/
errno_t mutex_lock_timeout(mutex_t *mtx, uint32_t usec)
{
if (usec != 0) {
assert(mtx->type != MUTEX_ACTIVE);
assert(THREAD);
}
if (mtx->type == MUTEX_RECURSIVE && mtx->owner == THREAD) {
assert(THREAD);
mtx->nesting++;
return EOK;
}
errno_t rc = semaphore_down_timeout(&mtx->sem, usec);
if (rc == EOK) {
mtx->owner = THREAD;
mtx->nesting = 1;
}
return rc;
}
/** Attempt to acquire mutex without blocking.
*
* @return EOK if lock was successfully acquired, something else otherwise.
*/
errno_t mutex_trylock(mutex_t *mtx)
{
return mutex_lock_timeout(mtx, 0);
}
/** Release mutex.
*
* @param mtx Mutex.
*/
void mutex_unlock(mutex_t *mtx)
{
if (mtx->type == MUTEX_RECURSIVE) {
assert(mtx->owner == THREAD);
if (--mtx->nesting > 0)
return;
mtx->owner = NULL;
}
semaphore_up(&mtx->sem);
}
/** @}
*/