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    SubjectRe: [PATCH 4/4] TTY: call tty_driver_lookup_tty unconditionally
    On 10/12/2011 11:32 AM, Jiri Slaby wrote:
    > Commit 4a2b5fddd5 (Move tty lookup/reopen to caller) made the call to
    > tty_driver_lookup_tty conditional in tty_open. It doesn't look like it
    > was an intention. Or if it was, it was not documented in the changelog
    > and the code now looks weird. For example there would be no need to
    > remember the tty driver and tty index. Further the condition depends
    > on a tty which we drop a reference of already.
    >
    > If I'm looking correctly, this should not matter thanks to the locking
    > currently done there. Thus, tty_driver->ttys[idx] cannot change under
    > our hands. But anyway, it makes sense to change that to the old
    > behaviour.

    Well, this doesn't work for ptys. devpts lookup code expects an inode to
    be one of devpts filesystem (/dev/pts/*), not something on tmpfs like
    /dev/tty. So it looks like the change was intentional, but very
    undocumented and leaving there some unused code.

    Now, I don't know what to do with the tty being around with a dropped
    reference. Maybe nothing in the presence of the BTM which I *think*
    prevents tty to go now.

    Also I have just found that having ptm_unix98_lookup is pointless. For
    master, we have ptmx_open which doesn't call lookup. And if it did, it
    would trigger BUG_ON in devpts_get_tty called from ptm_unix98_lookup.

    thanks,
    --
    js


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