[patch 0/3] Re: tty contention resulting from tty_open_by_device export

From: Okash Khawaja
Date: Sun Jul 09 2017 - 07:44:39 EST

On Sat, Jul 08, 2017 at 10:38:03AM +0200, Greg Kroah-Hartman wrote:
> Overall, the idea looks sane to me. Keeping userspace from opening a
> tty that the kernel has opened internally makes sense, hopefully
> userspace doesn't get too confused when that happens. I don't think we
> normally return -EBUSY from an open call, have you seen what happens
> with apps when you do this (like minicom?)
I tested this wil minincom, picocom and commands like "echo foo >
/dev/ttyS0". They all correctly report "Device or resource busy".

I have addressed all the comments you made. I have also split the patch
into three. Following is summary of each.

Patch 1: introduces the tty_kopen function and checks for TTY_KOPENED
Patch 2: updates speakup code to use tty_kopen instead of
Patch 3: reverses the export of tty_open_by_driver