From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Tue, 1 Jul 2014 18:26:57 +0000 (-0700)
Subject: rcu: Provide cond_resched_rcu_qs() to force quiescent states in long loops
X-Git-Tag: fixes-against-v3.18-rc2~103^2~1^2~15^2~16
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bde6c3aa993066acb0d6ce32ecabe03b9d5df92d;p=pandora-kernel.git

rcu: Provide cond_resched_rcu_qs() to force quiescent states in long loops

RCU-tasks requires the occasional voluntary context switch
from CPU-bound in-kernel tasks.  In some cases, this requires
instrumenting cond_resched().  However, there is some reluctance
to countenance unconditionally instrumenting cond_resched() (see
http://lwn.net/Articles/603252/), so this commit creates a separate
cond_resched_rcu_qs() that may be used in place of cond_resched() in
locations prone to long-duration in-kernel looping.

This commit currently instruments only RCU-tasks.  Future possibilities
include also instrumenting RCU, RCU-bh, and RCU-sched in order to reduce
IPI usage.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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