From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Mon, 25 Jun 2012 15:41:11 +0000 (-0700)
Subject: rcu: Allow RCU quiescent-state forcing to be preempted
X-Git-Tag: omap-for-v3.7-rc1/fixes-cpufreq-signed~101^2~1^2~15
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b4be093fee0200789df59b6c90e2d099a20f55b3;p=pandora-kernel.git

rcu: Allow RCU quiescent-state forcing to be preempted

RCU quiescent-state forcing is currently carried out without preemption
points, which can result in excessive latency spikes on large systems
(many hundreds or thousands of CPUs).  This patch therefore inserts
a voluntary preemption point into force_qs_rnp(), which should greatly
reduce the magnitude of these spikes.

Reported-by: Mike Galbraith <mgalbraith@suse.de>
Reported-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
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