linux-kernel - Re: tty idle time and hooking inode

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Message-ID: <4EEBA0CB.1050006@cfl.rr.com>
Date:	Fri, 16 Dec 2011 14:49:31 -0500
From:	Phillip Susi <psusi@....rr.com>
To:	Greg KH <gregkh@...e.de>
CC:	linux-kernel@...r.kernel.org
Subject: Re: tty idle time and hooking inode_ops from a chardev

On 12/16/2011 1:36 PM, Greg KH wrote:
> As you are opening the tty node once, that's when atime is set, right?
> The fact that you keep it open still keeps the atime to the original
> open time, you aren't supposed to check for every single read/write of
> the node once it was opened.
>
> But to be sure, what does POSIX say about this?

Actually it looks like POSIX 4.8 "File Times Update" requires the 
timestamps to be updated on every read/write, which is probably why 
Linux does that.

So the problem is just the /dev/tty alias having a different inode than 
the actual controlling tty.  It also makes the output of lsof less 
useful, so maybe the real fix is to somehow make opening /dev/tty 
actually open the correct tty inode and dentry.

I have a feeling that will require changing /dev/tty from being a 
devnode to a symlink to something in /dev/pts.
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