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

[Viresh Kumar]

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);

-- 
viresh