//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:       Locks and synchronization                                     //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2019 The OS/K Team                                       //
//                                                                            //
//  This file is part of OS/K.                                                //
//                                                                            //
//  OS/K 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         //
//  any later version.                                                        //
//                                                                            //
//  OS/K 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 OS/K.  If not, see <https://www.gnu.org/licenses/>.            //
//----------------------------------------------------------------------------//

#ifndef _KALBASE_H
#include <kalbase.h>
#endif

#ifdef _KALEID_KERNEL

#ifndef _KALKERN_PANIC_H
#include <kernel/panic.h>
#endif

#endif

#ifndef _KALEXTRAS_LOCKS_H
#define _KALEXTRAS_LOCKS_H

#ifdef __cplusplus
extern "C" {
#endif

typedef enum LockType_t         LockType_t;
typedef struct Lock_t           Lock_t;

//------------------------------------------//

enum LockType_t
{
    // Mutex-type lock
    //
    // WARNING
    //      AcquireLock() panics when used on a mutex while not running a process
    KLOCK_MUTEX,

    // Spinlock-type lock
    KLOCK_SPINLOCK,

};

struct Lock_t
{
    unsigned int    initDone;
    LockType_t      type;
    volatile int    locked;

/* #ifdef _KALEID_KERNEL
    Thread_t       *ownerThread;    // unused
    Thread_t       *waitingThread;  // unused
#endif */
};

//------------------------------------------//

#ifndef _KALEID_KERNEL
int KalYieldCPU(void),
#endif

//
// Initialize a lock
//
static inline
void ExInitLock(Lock_t *lock, LockType_t type)
{
    lock->type = type;
    lock->locked = FALSE;
    lock->initDone = INITOK;
/* #ifdef _KALEID_KERNEL
    lock->ownerThread = NULL;
    lock->waitingThread = NULL;
#endif */
}

//
// Alternative way to initalize a lock
//
#ifdef _KALEID_KERNEL
#   define ExINITLOCK(type)    { INITOK, FALSE, (type), /* NULL, NULL */ }
#else
#   define ExINITLOCK(type)    { INITOK, FALSE, (type) }
#endif

//
// Destroy a lock
//
static inline
void ExDestroyLock(Lock_t *lock)
{
    KalAssert(lock->initDone);

    __sync_synchronize();
    lock->initDone = 0;
}

//
// Acquire the lock
// Panic on double acquisition since that should never happen
// until we have at least a basic scheduler
//
static inline
void ExAcquireLock(Lock_t *lock)
{
    KalAssert(lock->initDone == INITOK);

    while (!__sync_bool_compare_and_swap(&lock->locked, 0, 1)) {
#ifdef _KALEID_KERNEL
        KeStartPanic("AcquireLock on an already locked object");
#else
        if likely (lock->type == KLOCK_SPINLOCK) continue;
        else (void)KalYieldCPU();
#endif
    }
    __sync_synchronize();
}

//
// Release an already acquired lock
// Panic if the lock was never acquired
//
static inline
void ExReleaseLock(Lock_t *lock)
{
/*#ifdef _KALEID_KERNEL
    KalAssert(lock->ownerThread == GetCurThread());
#endif*/

    __sync_synchronize();
    lock->locked = 0;
}

//
// Tries to acquire lock
//
static inline
bool ExAttemptLock(Lock_t *lock)
{
    KalAssert(lock->initDone == INITOK);

    bool retval = __sync_bool_compare_and_swap(&lock->locked, 0, 1);

    __sync_synchronize();

    return retval;
}

//------------------------------------------//

#ifdef __cplusplus
}
#endif

#endif