tree 958d6da99e73bf1834492b2ab17702087126abc0
parent ee0bab83ce65b6f6910cfc0c8278351a0583531b
author Peter Hurley <peter@hurleysoftware.com> 1374583650 -0400
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1374622983 -0700

n_tty: Special case pty flow control

The pty driver forces ldisc flow control on, regardless of available
receive buffer space, so the writer can be woken whenever unthrottle
is called. However, this 'forced throttle' has performance
consequences, as multiple atomic operations are necessary to
unthrottle and perform the write wakeup for every input line (in
canonical mode).

Instead, short-circuit the unthrottle if the tty is a pty and perform
the write wakeup directly.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>