linux-kernel - Re: [PATCH] Remove pty_ops_bsd and pty_bsd

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Date:	Tue, 29 Sep 2009 09:23:31 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	David Howells <dhowells@...hat.com>
cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, akpm@...ux-foundation.org,
	gregkh@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Remove pty_ops_bsd and pty_bsd_ioctl() as they're not
 used

On Tue, 29 Sep 2009, David Howells wrote:
> 
> Is it right to use pty_ops_bsd in _both_ places?  Looking at the code in
> linux-2.6.0, the BSD ioctl only applies to the master and doesn't apply to the
> slave.

Right you are, good catch.

That said, I have to say that this whole pty lock thing seems to have been 
broken since 2.6.26, and even now, nobody actually _complained_. You found 
the problem due to a compiler warning rather than due to somebody noticing 
that pty_bsd_ioctl() is no longer hooked up.

Because as far as I can tell, the bug was introduced by commit 
3e8e88ca053150efdbecb45d8f481cf560ec808d ("pty: prepare for tty->ops 
changes") back in April of 2008. That added the whole 'pty_ops_bsd' 
structure, but it has never actually been used.

So I do wonder whether the right thing to do would not be to simple remove 
the whole pty_ops_bsd code entirely. Or maybe mode the trivial TIOCSPTLCK 
into the generic tty ioctl handling, and just make it test for 
"driver->subtype == PTY_TYPE_MASTER" - and at least get rid of this subtle 
thing that was broken for over a year without anybody noticing..

		Linus
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