From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Wed, 20 Jun 2012 00:18:20 +0000 (-0700)
Subject: rcu: Allow RCU grace-period initialization to be preempted
X-Git-Tag: omap-for-v3.7-rc1/fixes-cpufreq-signed~101^2~1^2~23
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=755609a9087fa983f567dc5452b2fa7b089b591f;p=pandora-kernel.git

rcu: Allow RCU grace-period initialization to be preempted

RCU grace-period initialization is currently carried out with interrupts
disabled, which can result in 200-microsecond latency spikes on systems
on which RCU has been configured for 4096 CPUs.  This patch therefore
makes the RCU grace-period initialization be preemptible, which should
eliminate those latency spikes.  Similar spikes from grace-period cleanup
and the forcing of quiescent states will be dealt with similarly by later
patches.

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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