Re: [linux-usb-devel] [RFC] HID bus design overview.

Li Yu
2007-04-05T06:48:36Z

Dmitry Torokhov wrote:
>>> +int hid_open(struct hid_device *hid)
>>> +{
>>> + struct hid_transport *tl;
>>> + int ret;
>>> +
>>> + if (hid->driver->open)
>>> + return hid->driver->open(hid);
>>> + ret = 0;
>>> + spin_lock(&hid_lock);
>>> + tl = hid_transports[hid->bus];
>>> + if (tl->open)
>>> + ret = tl->open(hid);
>>> + spin_unlock(&hid_lock);
>>> + return ret;
>>> +}
>>>
>>>
>> Spinlock is not the best choise here, I'd expect most ->open()
>> implementation wait on some IO.
>>
>>
>>
> Yes, I agree! Also, there have another code access hid_transports[]
> without spin it!
>
>
I think I found out the resolve means for this: using the refcnt of
hid_transport->module,
so we can read access hid_transports[] safely without any lock protection.