From a10bf26b2f53242836e9362c6c9c857b627b82a9 Mon Sep 17 00:00:00 2001
From: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Date: Wed, 8 Feb 2012 14:15:42 -0500
Subject: [PATCH] ima: replace iint spinblock with rwlock/read_lock

For performance, replace the iint spinlock with rwlock/read_lock.

Eric Paris questioned this change, from spinlocks to rwlocks, saying
"rwlocks have been shown to actually be slower on multi processor
systems in a number of cases due to the cache line bouncing required."

Based on performance measurements compiling the kernel on a cold
boot with multiple jobs with/without this patch, Dmitry Kasatkin
and I found that rwlocks performed better than spinlocks, but very
insignificantly.  For example with total compilation time around 6
minutes, with rwlocks time was 1 - 3 seconds shorter... but always
like that.

Changelog v2:
- new patch taken from the 'allocating iint improvements' patch

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
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