Re: [Update][RFC/RFT][PATCH v3 2/5] driver core: Functional dependencies tracking support

[Rafael J. Wysocki]

On Tue, Sep 27, 2016 at 10:54 AM, Lukas Wunner <lukas@xxxxxxxxx> wrote:
> On Fri, Sep 16, 2016 at 02:33:55PM +0200, Rafael J. Wysocki wrote:
>> +void device_links_unbind_consumers(struct device *dev)
>> +{
>> +     struct device_link *link;
>> +     int idx;
>> +
>> + start:
>> +     idx = device_links_read_lock();
>> +
>> +     list_for_each_entry_rcu(link, &dev->links_to_consumers, s_node) {
>> +             enum device_link_status status;
>> +
>> +             if (link->flags & DEVICE_LINK_STATELESS)
>> +                     continue;
>> +
>> +             spin_lock(&link->lock);
>> +             status = link->status;
>> +             if (status == DEVICE_LINK_CONSUMER_PROBE) {
>> +                     spin_unlock(&link->lock);
>> +
>> +                     device_links_read_unlock(idx);
>> +
>> +                     wait_for_device_probe();
>> +                     goto start;
>> +             }
>
> While revisiting this function it just occurred to me that there's
> a theoretical infinite loop here if the consumer probes, is unbound
> by the supplier, then reprobes again before the supplier had a chance
> to update the link to DEVICE_LINK_SUPPLIER_UNBIND.  Perhaps this isn't
> a problem in practice, but noting anyway.

But the consumer is unbound only after setting the link status to
DEVICE_LINK_SUPPLIER_UNBIND and then it won't probe again.

Or am I overlooking something?

Thanks,
Rafael