From: Ivo Sieben <meltedpianoman@gmail.com>
Date: Wed, 17 Oct 2012 12:03:14 +0000 (+0200)
Subject: tty: Use raw spin lock to protect TTY ldisc administration
X-Git-Tag: omap-for-v3.8/fixes-for-merge-window-v4-signed~83^2~114
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c97399418a25b18943c9910fb28e0ee5ecc3c316;p=pandora-kernel.git

tty: Use raw spin lock to protect TTY ldisc administration

The global "normal" spin lock that guards the line discipline
administration is replaced by a raw spin lock. On a PREEMPT_RT system this
prevents unwanted scheduling overhead around the line discipline administration.

On a 200 MHz AT91SAM9261 processor setup this fixes about 100us of scheduling
overhead on a TTY read or write call.

Signed-off-by: Ivo Sieben <meltedpianoman@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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