Re: [PATCH v10] i2c: virtio: add a virtio i2c frontend driver

Jie Deng
2021-03-24T00:54:19Z

On 2021/3/23 17:38, Viresh Kumar wrote:
> On 23-03-21, 14:31, Viresh Kumar wrote:
>> On 23-03-21, 22:19, Jie Deng wrote:
>>> +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
>>> +{
>>> + struct virtio_i2c *vi = i2c_get_adapdata(adap);
>>> + struct virtqueue *vq = vi->vq;
>>> + struct virtio_i2c_req *reqs;
>>> + unsigned long time_left;
>>> + int ret, nr;
>>> +
>>> + reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL);
>>> + if (!reqs)
>>> + return -ENOMEM;
>>> +
>>> + mutex_lock(&vi->lock);
>>> +
>>> + ret = virtio_i2c_send_reqs(vq, reqs, msgs, num);
>>> + if (ret == 0)
>>> + goto err_unlock_free;
>>> +
>>> + nr = ret;
>>> + reinit_completion(&vi->completion);
>> I think I may have found a possible bug here. This reinit_completion() must
>> happen before we call virtio_i2c_send_reqs(). It is certainly possible (surely
>> in corner cases) that virtio_i2c_msg_done() may get called right after
>> virtio_i2c_send_reqs() and before we were able to call reinit_completion(). And
>> in that case we will never see the completion happen at all.
>>
>>> + virtqueue_kick(vq);
> I may have misread this. Can the actually start before virtqueue_kick() is
> called ?

No. It starts when wait_for_completion_timeout is called.

So it should be fine here.

> If not, then completion may be fine where it is.
>