From a183561567b5446d3362b4839bd4f744f4b2af1e Mon Sep 17 00:00:00 2001
From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Date: Fri, 25 Jan 2008 21:08:00 +0100
Subject: [PATCH] sched: introduce a mutex and corresponding API to serialize
 access to doms_curarray

doms_cur[] array represents various scheduling domains which are
mutually exclusive. Currently cpusets code can modify this array (by
calling partition_sched_domains()) as a result of user modifying
sched_load_balance flag for various cpusets.

This patch introduces a mutex and corresponding API (only when
CONFIG_FAIR_GROUP_SCHED is defined) which allows a reader to safely read
the doms_cur[] array w/o worrying abt concurrent modifications to the
array.

The fair group scheduler code (introduced in next patch of this series)
makes use of this mutex to walk thr' doms_cur[] array while rebalancing
shares of task groups across cpus.

Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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