tty: Only wakeup the line discipline idle queue when queue is active
authorIvo Sieben <meltedpianoman@gmail.com>
Tue, 18 Dec 2012 14:48:50 +0000 (15:48 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 16 Jan 2013 07:02:22 +0000 (23:02 -0800)
commitbd5d7ce9afdd0cddc5ab65e20d1134ccad824418
tree2bfffe6ab96beedc8410c70a32334951cc14ecac
parentb342dd512f7af0e0e14e29c3e1f863150cfc46ff
tty: Only wakeup the line discipline idle queue when queue is active

Before waking up the tty line discipline idle queue first check if the queue is
active (non empty). This prevents unnecessary entering the critical section in
the wake_up() function and therefore avoid needless scheduling overhead on a
PREEMPT_RT system caused by two processes being in the same critical section.

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