path: root/src/common/spinlock.h

#pragma once
#ifndef _rA_SPINLOCK_H_
#define _rA_SPINLOCK_H_

//
// CAS based Spinlock Implementation
//
// CamelCase names are choosen to be consistent with microsofts winapi
// which implements CriticalSection by this naming...
//
// Author: Florian Wilkemeyer <fw@f-ws.de>
//
// Copyright (c) rAthena Project (www.rathena.org) - Licensed under GNU GPL
// For more information, see LICENCE in the main folder
//
//

#ifdef WIN32
#include "../common/winapi.h"
#endif

#include "../common/cbasetypes.h"
#include "../common/atomic.h"
#include "../common/thread.h"

#ifdef WIN32

typedef struct __declspec(align(64)) SPIN_LOCK {
    volatile LONG lock;
    volatile LONG nest;
    volatile LONG sync_lock;
}  SPIN_LOCK, *PSPIN_LOCK;
#else
typedef struct SPIN_LOCK {
    volatile int32 lock;
    volatile int32 nest; // nesting level.

    volatile int32 sync_lock;
} __attribute__((aligned(64))) SPIN_LOCK, *PSPIN_LOCK;
#endif



static forceinline void InitializeSpinLock(PSPIN_LOCK lck)
{
    lck->lock = 0;
    lck->nest = 0;
    lck->sync_lock = 0;
}

static forceinline void FinalizeSpinLock(PSPIN_LOCK lck)
{
    return;
}


#define getsynclock(l) { while(1){ if(InterlockedCompareExchange(l, 1, 0) == 0) break; rathread_yield(); } }
#define dropsynclock(l) { InterlockedExchange(l, 0); }

static forceinline void EnterSpinLock(PSPIN_LOCK lck)
{
    int tid = rathread_get_tid();

    // Get Sync Lock && Check if the requester thread already owns the lock.
    // if it owns, increase nesting level
    getsynclock(&lck->sync_lock);
    if (InterlockedCompareExchange(&lck->lock, tid, tid) == tid) {
        InterlockedIncrement(&lck->nest);
        dropsynclock(&lck->sync_lock);
        return; // Got Lock
    }
    // drop sync lock
    dropsynclock(&lck->sync_lock);


    // Spin until we've got it !
    while (1) {

        if (InterlockedCompareExchange(&lck->lock, tid, 0) == 0) {

            InterlockedIncrement(&lck->nest);
            return; // Got Lock
        }

        rathread_yield(); // Force ctxswitch to another thread.
    }

}


static forceinline void LeaveSpinLock(PSPIN_LOCK lck)
{
    int tid = rathread_get_tid();

    getsynclock(&lck->sync_lock);

    if (InterlockedCompareExchange(&lck->lock, tid, tid) == tid) { // this thread owns the lock.
        if (InterlockedDecrement(&lck->nest) == 0)
            InterlockedExchange(&lck->lock, 0); // Unlock!
    }

    dropsynclock(&lck->sync_lock);
}




#endif