在 linux 内核代码中，当自旋锁被锁定时，spin_lock 函数将自旋。spin_lock 的代码如下：
static __always_inline void __ticket_spin_lock(raw_spinlock_t *lock)
{
int inc = 0x00010000;
int tmp;
asm volatile(LOCK_PREFIX "xaddl %0, %1\n"
"movzwl %w0, %2\n\t"
"shrl $16, %0\n\t"
"1:\t"
"cmpl %0, %2\n\t"
"je 2f\n\t"
"rep ; nop\n\t"
"movzwl %1, %2\n\t"
/* don't need lfence here, because loads are in-order */
"jmp 1b\n"
"2:"
: "+r" (inc), "+m" (lock->slock), "=&r" (tmp)
:
: "memory", "cc");
}
我的问题是：
如何添加计时器来监控锁的旋转时间？请给我一些建议。