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Date: Thu, 19 Sep 2002 08:12:31 -0700 (PDT)
From: Linus Torvalds <torvalds@transmeta.com>
To: William Lee Irwin III <wli@holomorphy.com>
cc: Ingo Molnar <mingo@elte.hu>, <linux-kernel@vger.kernel.org>
Subject: Re: [patch] generic-pidhash-2.5.36-D4, BK-curr
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On Thu, 19 Sep 2002, William Lee Irwin III wrote:
> 
> I did this intentionally. Basically, sys_setsid() does the right thing,
> but tty_ioctl() does not. There is already some inconsistency
> about how task->tty is locked, and I'd not yet come to a conclusion.

I agree about the locking issue (although I do _not_ believe that the
tasklock should have anything to do with the tsk->tty locking - it should
most likely use some per-task lock for the actual tty accesses, together
with the optimization that a write lock on the tasklock is sufficient to
protect it because it means that nobody else can look up the task).

However, what I worry about is that there may not (will not) be a 1:1
session<->tty thing. In particular, when somebody creates a new session 
with "setsid()", that does not remove the tty from processes that used to 
hold it, I think (this is all from memory, so I might be wrong).

Which means that if the tty is going away, it has to be removed from _all_ 
tasks, not just from the one session that happened to be the most recent 
one.

		Linus

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