[patch 1/6] tty_port: allow a port to be opened with a tty that has no file handle

[Okash Khawaja]

Hi,

On Mon, May 22, 2017 at 11:07 PM, Samuel Thibault
<samuel.thibault at ens-lyon.org> wrote:
> Hello,
>
> Okash Khawaja, on mer. 17 mai 2017 14:38:32 +0100, wrote:
>> On Wed, May 17, 2017 at 09:45:46AM +0200, Samuel Thibault wrote:
>> > > This issue with opening tty from userspace while it's in use from kernel. Wonder
>> > > if this will rear its ugly head with rescpect to the recent patches?
>> >
>> > Ah, yes, we will have to think about that issue.
>>
>> Would you suggest me raising this with Alan Cox as he mentioned some
>> locking to prevent this scenario?
>
> Mmm, I don't see which locking you refer to, I don't remember Alan Cox
> talking about it?
It's in the same RFC patch that from Alan:
http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1215095.html

Here's quote:

    "It doesn't deal with the case of a user opening a port that's also kernel
    opened and that would need some locking out (so it returned EBUSY if bound
    to a kernel device of some kind)."

> AFAICS, tty_open() will just always manage to open
> the tty, and reach the check_tty_count() call.
Yes. Wonder if that is okay then or do we need to do something about it?

Thanks,
Okash