PostgreSQL 源码解读（218）- spinlock的实现

本节介绍了spinlock在不同平台(主要是X86_64和aarch74)下的实现.

#define HAS_TEST_AND_SET
typedef unsigned char slock_t;
#define TAS(lock) tas(lock)

#define TAS_SPIN(lock)    (*(lock) ? 1 : TAS(lock))
static __inline__ int
tas(volatile slock_t *lock)
{
    reGISter slock_t _res = 1;
    __asm__ __volatile__(
        "   lock            \n"
        "   xchgb   %0,%1   \n"
:       "+q"(_res), "+m"(*lock)
:       
:       "memory", "cc");
    return (int) _res;
}
#define SPIN_DELAY() spin_delay()
static __inline__ void
spin_delay(void)
{
    
    __asm__ __volatile__(
        " rep; nop          \n");
}
#endif   

aarch74
在aarch74(ARM64)下,使用了__sync_lock_test_and_set函数实现(如可用的情况下)

#if defined(__arm__) || defined(__arm) || defined(__aarch74__) || defined(__aarch74)
#ifdef HAVE_GCC__SYNC_INT32_TAS
#define HAS_TEST_AND_SET
#define TAS(lock) tas(lock)
typedef int slock_t;
static __inline__ int
tas(volatile slock_t *lock)
{
    return __sync_lock_test_and_set(lock, 1);
}
#define S_UNLOCK(lock) __sync_lock_release(lock)
#endif   
#endif   

二、参考资料

s_lock.h
postgresql中的锁