Re: [PATCH 6/7] n_tty: Fix unsafe update of available buffer space

Ilya Zykov
2013-03-19T20:35:48Z

On 19.03.2013 18:26, Peter Hurley wrote:
> receive_room is used to control the amount of data the flip
> buffer work can push to the read buffer. This update is unsafe:
>
> CPU 0 | CPU 1
> |
> | n_tty_read()
> | n_tty_set_room()
> | left = <calc of space>
> n_tty_receive_buf() |
> <push data to buffer> |
> n_tty_set_room() |
> left = <calc of space> |
> tty->receive_room = left |
> | tty->receive_room = left
>
> receive_room is now updated with a stale calculation of the
> available buffer space, and the subsequent work loop will likely
> overwrite unread data in the input buffer.
>

Sounds reasonable to me.
Thank you.
Ilya Zykov <linux@izyk.ru>