Re: Ptyfs correction.

[Ilia Zykov <netbsd%izyk.ru@localhost>]

On 15.10.2014 16:55, Christos Zoulas wrote:
> On Oct 15,  1:14pm, netbsd%izyk.ru@localhost (Ilia Zykov) wrote:
> -- Subject: Re: Ptyfs correction.
>
> | Hello!
> |  - corrects some wrong comments
> |  - add XXX warning
> |  - increase security
> |  - make pty_vn_open() private to tty_ptm.c
> | 
> | Thank you.
> | Ilia.
>
> Can you please explain this:
>
> -       if (type == PTYFSptc)
> +       /* Activate node only after we have grabbed device. */
> +       if (type == PTYFSpts)
>
>
> Thanks.
> christos
>

On SMP systems(with ptyfs multiple mounts) in this point (type ==
PTYFSptc) can be multiple threads.
Afterwards "ptm" driver leave only one(all other will grab other
devices), but will be time before ptyfs_inactive(),
when its will be have active this node for other mount points.
After, when "ptm" has grabbed device for this thread, it calls this
function only for one winner thread
with type == PTYFSpts.  It's situation very difficult usage because we
do VOP_REVOKE(), but theoretically
possible. And more reliable activate device only at one mount point when
we have grabbed device.

Ilia.