RE: [PATCH] PCI: hv: Do not wait forever on a device that has disappeared

[Dexuan Cui <decui@microsoft.com>]

> From: Andy Shevchenko <andy.shevchenko@gmail.com>
> Sent: Tuesday, May 29, 2018 14:21
> On Thu, May 24, 2018 at 12:12 AM, Dexuan Cui <decui@microsoft.com>
> wrote:
> >
> > Before the guest finishes the device initialization, the device can be
> > removed anytime by the host, and after that the host won't respond to
> > the guest's request, so the guest should be prepared to handle this
> > case.
> 
> > +       while (true) {
> > +               if (hdev->channel->rescind) {
> > +                       dev_warn_once(&hdev->device, "The device is
> gone.\n");
> > +                       return -ENODEV;
> > +               }
> > +
> > +               if (wait_for_completion_timeout(comp, HZ / 10))
> > +                       break;
> > +       }
> 
> Infinite loops are usually a red flags.
> 
> What's wrong with simple:
> 
> do {
>   ...
> } while (wait_...(...) == 0);
> 
> ?
Thanks for the suggestion, Andy!
The coding style you suggested looks better to me. :-)

> > +       if (!ret)
> > +               ret = wait_for_response(hdev, &comp);
> 
> Better to use well established patterns, i.e.
> 
> if (ret)
>  return ret;
Agreed.

> 
> > +               if (!ret)
> > +                       ret = wait_for_response(hdev,
> &comp_pkt.host_event);
> 
> Here it looks okay on the first glance, but better to think about it
> again and refactor.

> With Best Regards,
> Andy Shevchenko

I'll try to send out a patch to improve the coding style, after I address
Michael Kelley's concern of a race.

Thanks,
-- Dexuan