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From 736d081ecb434beb9c4d738fb6ec2a185f52196a Mon Sep 17 00:00:00 2001
From: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Date: Fri, 3 Jul 2009 08:44:09 -0500
Subject: [PATCH] sched: Fix spurious load spikes
commit b97d674747b5499e4942d0297fb2a90757c4f519 in tip.
Fixes spurious system load spikes observed in /proc/loadavgrt, as described in:
Bug 253103: /proc/loadavgrt issues weird results
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=253103
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
kernel/sched.c | 7 +++++++
1 files changed, 7 insertions(+), 0 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index ff58409..17cef67 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3139,6 +3139,13 @@ unsigned long nr_iowait(void)
for_each_possible_cpu(i)
sum += atomic_read(&cpu_rq(i)->nr_iowait);
+ /*
+ * Since we read the counters lockless, it might be slightly
+ * inaccurate. Do not allow it to go below zero though:
+ */
+ if (unlikely((long)sum < 0))
+ sum = 0;
+
return sum;
}
--
1.7.0.4
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