myvtm/Framework/libtoolkit/spinlock.h

#ifndef __SPINLOCK_H__
#define __SPINLOCK_H__

#pragma once

#include "config.h"
#include "dbgutil.h"
#if _WIN32
  #include <intrin.h>
#endif
#include <assert.h>
#include <winpr/interlocked.h>

#ifdef __cplusplus
extern "C" {
#endif

typedef volatile LONG lock_t[1];

#define FASTLOCK_INIT()	{0}

/* "REP NOP" is PAUSE, coded for tools that don't know it by that name. */
#if (defined(__GNUC__) || defined(__clang__)) && (defined(__i386__) || defined(__x86_64__))
    #define PAUSE_INSTRUCTION() __asm__ __volatile__("pause\n")  /* Some assemblers can't do REP NOP, so go with PAUSE. */
#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
    #define PAUSE_INSTRUCTION() _mm_pause()  /* this is actually "rep nop" and not a SIMD instruction. No inline asm in MSVC x86-64! */
#elif defined(__WATCOMC__) && defined(__386__)
    /* watcom assembler rejects PAUSE if CPU < i686, and it refuses REP NOP as an invalid combination. Hardcode the bytes.  */
    extern _inline void PAUSE_INSTRUCTION(void);
    #pragma aux PAUSE_INSTRUCTION = "db 0f3h,90h"
#else
    #define PAUSE_INSTRUCTION()
#endif

// non-reentrance

static __inline void fastlock_init(lock_t l)
{
	l[0] = 0;
}

TOOLKIT_API void fastlock_enter(lock_t l);

static __inline void fastlock_leave(lock_t l)
{
	_ReadWriteBarrier();
	InterlockedExchange(l, 0);
}

static __inline void fastlock_term(lock_t l)
{
	TOOLKIT_ASSERT(l[0] == 0);
}

/* spin lock, note: reentrance!!! 
 * 11 1111 1111
 */

#define DEFAULT_SPIN_COUNT	0x3ff

// because zero is invalid thread id, so when a thread retrieve the lock 
// _value is set to the thread's id. 
typedef struct spinlock_t {
	volatile DWORD _value; 
	volatile DWORD _reentrance;
}spinlock_t;



static __inline void spinlock_init(spinlock_t *plock) 
{
	plock->_value = 0;
	plock->_reentrance = 0;
}

/**
 * enter lock
 * @param spin_count -1 use default
 */
TOOLKIT_API void spinlock_enter(volatile spinlock_t *sl, int spin_count);

/**
 * leave lock
 */
TOOLKIT_API void spinlock_leave(volatile spinlock_t *sl);



union rw_spinlock_barrier {
	struct {
		unsigned int readerCount    : 32 / 2;
		unsigned int writerCount    : 32 / 2 - 1;
		unsigned int writerActive   : 1 ;
	};
	unsigned int         nAtomic			;
};

typedef volatile struct rw_spinlock_s {
	union rw_spinlock_barrier barrier;
}rw_spinlock_t;

static __inline void rw_spinlock_init(rw_spinlock_t *rwlock)
{
	rwlock->barrier.nAtomic = 0;
}

// John M. Mellor-Crummey, Michael L. Scott "Scalable Reader-Writer Synchronization for Shared-Memory Multiprocessors", 1991

TOOLKIT_API void rw_spinlock_read_lock(rw_spinlock_t *rwlock);
TOOLKIT_API void rw_spinlock_read_unlock(rw_spinlock_t *rwlock);
TOOLKIT_API void rw_spinlock_write_lock(rw_spinlock_t *rwlock);
TOOLKIT_API void rw_spinlock_write_unlock(rw_spinlock_t *rwlock);

static __inline int rw_spinlock_is_reading(rw_spinlock_t *rwlock)
{
	return rwlock->barrier.readerCount != 0;
}

static __inline int rw_spinlock_is_writing(rw_spinlock_t *rwlock)
{
	return rwlock->barrier.writerActive == 1 ;
}

#ifdef __cplusplus
} // extern "C" {
#endif

#endif //__SPINLOCK_H__