To: linux-kernel@vger.kernel.org
From: hpa@zytor.com (H. Peter Anvin)
Subject: Re: something funny about tty's on 2.6.4-rc1-mm1
Date: Tue, 2 Mar 2004 05:47:27 +0000 (UTC)
Organization: Transmeta Corporation, Santa Clara CA
Message-ID: <c2175f$6hn$1@terminus.zytor.com>
References: <20040301184512.GA21285@hobbes.itsari.int>
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Followup to:  <20040301184512.GA21285@hobbes.itsari.int>
By author:    Nuno Monteiro <nuno@itsari.org>
In newsgroup: linux.dev.kernel
> 
> I know for a fact that I don't have 157 logged in users (well, there's  
> only 45 processes running right now), and shouldn't pts' be recycled, and  
> a lower number be assigned? The last kernel I ran was 2.6.3, and none of  
> this happened.
> 
> My config is:
> 
> CONFIG_UNIX98_PTYS=y
> CONFIG_LEGACY_PTYS=y
> CONFIG_LEGACY_PTY_COUNT=512
> 
> and this is a plain jane static /dev -- not devfs nor udev. Despite the  
> supposedly 157 users logged in, /dev/pts only contains '358', which is  
> the one allocated to this instance of aterm right now.
> 
> nuno@hobbes:~$ ls -l /dev/pts
> total 0
> crw--w----    1 nuno     users    136, 102 Mar  1 18:41 358
> 
> In the mean time I'll fall back to 2.6.3.
> 

No need to, as there is no error (except that you need a newer libc or
ls to properly show the device number.)

As RBJ said, ptys are now recycled in pid-like fashion, which means
numbers won't be reused until wraparound happens.  This is good for
security/fault tolerance, at least to some minor degree.

	-hpa

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