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Commit 6d76bd26 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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n_tty: Make N_TTY ldisc receive path lockless



n_tty has a single-producer/single-consumer input model;
use lockless publish instead.

Use termios_rwsem to exclude both consumer and producer while
changing or resetting buffer indices, eg., when flushing. Also,
claim exclusive termios_rwsem to safely retrieve the buffer
indices from a thread other than consumer or producer
(eg., TIOCINQ ioctl).

Note the read_tail is published _after_ clearing the newline
indicator in read_flags to avoid racing the producer.

Drop read_lock spinlock.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent a73d3d69
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