怎么做{} while(0)在宏中工作？

在Linux内核中,do {} while(0)如何工作？
例如,

#define preempt_disable()    do { } while (0)

如何禁用抢占？

#define might_resched()    do { } while (0)

它是如何重新安排的？

类似地,我已经看到了互斥锁和其他宏的宏.这有什么用？我理解以下问题,但不是上面的例子.

#define foo(x)    do { do something } while(0)

编辑：

rt_mutex_lock的以下代码怎么样？

/**
 * rt_mutex_lock - lock a rt_mutex
 *
 * @lock: the rt_mutex to be locked
 */
void __sched rt_mutex_lock(struct rt_mutex *lock)
{
        might_sleep();
        rt_mutex_fastlock(lock,TASK_UNINTERRUPTIBLE,rt_mutex_slowlock);
}
EXPORT_SYMBOL_GPL(rt_mutex_lock);


/*
 * debug aware fast / slowpath lock,trylock,unlock
 *
 * The atomic acquire/release ops are compiled away,when either the
 * architecture does not support cmpxchg or when debugging is enabled.
 */

static inline int rt_mutex_fastlock(struct rt_mutex *lock,int state,int detect_deadlock,int (*slowfn)(struct rt_mutex *lock,struct hrtimer_sleeper *timeout,int detect_deadlock))
{
        if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock,NULL,current))) {
                rt_mutex_deadlock_account_lock(lock,current);
                return 0;
        } else{
                return slowfn(lock,state,detect_deadlock);
        }
}

我很困惑,因为rt_mutex_deadlock_account_lock是在内核中的两个位置定义的：

在kernel / rtmutex-debug.c中：

void rt_mutex_deadlock_account_lock(struct rt_mutex *lock,struct task_struct *task)
{
    //....
}

在kernel / rtmutex.h中：

#define rt_mutex_deadlock_account_lock(m,t) do { } while (0)

在i2c驱动程序rt_mutex_lock(& adap-> bus_lock)中的新内核2.6.35.4中;已经取代了mutex_lock().这怎么锁定呢？