i2c_transfer是内核里的读写接口函数
在这个函数里
if (in_atomic() || irqs_disabled()) {
ret = rt_mutex_trylock(&adap->bus_lock);
if (!ret)
/* I2C activity is ongoing. */
return -EAGAIN;
} else {
rt_mutex_lock(&adap->bus_lock);
}
/* Retry automatically on arbitration loss */
orig_jiffies = jiffies;
for (ret = 0, try = 0; try <= adap->retries; try++) {
ret = adap->algo->master_xfer(adap, msgs, num);
if (ret != -EAGAIN)
break;
if (time_after(jiffies, orig_jiffies + adap->timeout))
break;
}
rt_mutex_unlock(&adap->bus_lock);
有锁保护,rt_mutex_lock,但是有几点不是很明白:
1、rt_mutex_trylock在什么情况下会用到
2、如果一个访问真正进行,此时应该是lock住了,然后另外一个访问又来了,它在rt_mutex_lock时应该是lock不住的,那这次访问是会被打回还是等待前一次操作结束了,它再继续操作?Linux的rt_mutex_lock有这个等待的机制吗?
恳请各位大大解答小弟的疑惑