/*
 * Copyright 2009, Michael Lotz, mmlr@mlotz.ch.
 * Copyright 2008-2010, Ingo Weinhold, ingo_weinhold@gmx.de.
 * Copyright 2002-2009, Axel Dörfler, axeld@pinc-software.de. All rights reserved.
 * Distributed under the terms of the MIT License.
 *
 * Copyright 2001-2002, Travis Geiselbrecht. All rights reserved.
 * Distributed under the terms of the NewOS License.
 */


#include <locks.h>

#include <stdlib.h>
#include <string.h>

#include <syscalls.h>
#include <user_mutex_defs.h>


#define MAX_UNSUCCESSFUL_SPINS  100


extern int32 __gCPUCount;


// #pragma mark - mutex


void
__mutex_init(mutex *lock, const char *name)
{
        lock->name = name;
        lock->lock = 0;
        lock->flags = 0;
}


void
__mutex_init_etc(mutex *lock, const char *name, uint32 flags)
{
        lock->name = (flags & MUTEX_FLAG_CLONE_NAME) != 0 ? strdup(name) : name;
        lock->lock = 0;
        lock->flags = flags;

        if (__gCPUCount < 2)
                lock->flags &= ~uint32(MUTEX_FLAG_ADAPTIVE);
}


void
__mutex_destroy(mutex *lock)
{
        if ((lock->flags & MUTEX_FLAG_CLONE_NAME) != 0)
                free(const_cast<char*>(lock->name));
}


status_t
__mutex_lock(mutex *lock)
{
        uint32 count = 0;
        const uint32 kMaxCount
                = (lock->flags & MUTEX_FLAG_ADAPTIVE) != 0 ? MAX_UNSUCCESSFUL_SPINS : 1;

        int32 oldValue;
        do {
                oldValue = atomic_test_and_set(&lock->lock, B_USER_MUTEX_LOCKED, 0);
                if (oldValue == 0 || (oldValue & B_USER_MUTEX_DISABLED) != 0)
                        return B_OK;
        } while (count++ < kMaxCount && (oldValue & B_USER_MUTEX_WAITING) != 0);

        // we have to call the kernel
        status_t error;
        do {
                error = _kern_mutex_lock(&lock->lock, lock->name, 0, 0);
        } while (error == B_INTERRUPTED);

        return error;
}


void
__mutex_unlock(mutex *lock)
{
        // clear the locked flag
        int32 oldValue = atomic_and(&lock->lock, ~(int32)B_USER_MUTEX_LOCKED);
        if ((oldValue & B_USER_MUTEX_WAITING) != 0
                        && (oldValue & B_USER_MUTEX_DISABLED) == 0) {
                _kern_mutex_unblock(&lock->lock, 0);
        }

        if ((oldValue & B_USER_MUTEX_LOCKED) == 0)
                debugger("mutex was not actually locked!");
}