//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Authors:    spectral`                                                     //
//              NeoX                                                          //
//                                                                            //
//  Desc:       Spinlocks and mutexes                                         //
//----------------------------------------------------------------------------//

//------------------------------------------//
//              Dependencies                //
//------------------------------------------//

#ifdef _KALEID_KERNEL

#ifndef _KALKERN_BASE_H
#include "kernbase.h"
#endif

#else

#ifndef _KALEID_H
#include <kaleid.h>
#endif

#endif

//------------------------------------------//
//             Start of header              //
//------------------------------------------//

#ifndef _KALKERN_LOCKS_H
#define _KALKERN_LOCKS_H

//------------------------------------------//
//                  Types                   //
//------------------------------------------//

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

    //
    // Spinlock-type lock
    //
    KLOCK_SPINLOCK,

} LockType_t;

//
// "volatile" may not be actually needed
//
typedef struct sLock_t {
    unsigned int    initDone;       // initialized?
    int             locked;         // is locked?
    LockType_t      type;           // lock type?
#ifdef _KALEID_KERNEL
    Process_t      *ownerProc;      // unused
    Process_t      *waitingProc;    // unused
#endif
} volatile Lock_t;

//------------------------------------------//
//                Functions                 //
//------------------------------------------//

//
// Linux syscall...
//
#ifndef _KALEID_KERNEL
int sched_yield(void);
#endif

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

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

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

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

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

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

//
// Release an already aquired lock
// Panic if the lock was never aquired
//
static inline
void ReleaseLock(Lock_t *lock)
{
#ifdef _KALEID_KERNEL
    KalAssert(lock->ownerProc == GetCurProc());
#endif

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

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

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

    __sync_synchronize();

    return retval;
}

//------------------------------------------//
//              End of header               //
//------------------------------------------//

#endif