RE: [PATCH tty-next 14/22] tty: Remove tty_wait_until_sent_from_close()

[David Laight]

From: Peter Hurley
...
> > I don't understand the second half of the changelog, it doesn't seem
> > to fit here: there deadlock that we are trying to avoid here happens
> > when the *same* tty needs the lock to complete the function that
> > sends the pending data. I don't think we do still do that any more,
> > but it doesn't seem related to the tty lock being system-wide or not.
> 
> The tty lock is not used in the i/o path; it's purpose is to
> mutually exclude state changes in open(), close() and hangup().
> 
> The commit that added this [1] comments that _other_ ttys may wait
> for this tty to complete, and comments in the code note that this
> function should be removed when the system-wide tty mutex was removed
> (which happened with the commit noted in the changelog).

What happens if another process tries to do a non-blocking open
while you are sleeping in close waiting for output to drain?

Hopefully this returns before that data has drained.

	David

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