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sched/fair: Avoid using decay_load_missed() with a negative value 

decay_load_missed() cannot handle nagative values, so we need to prevent
using the function with a negative value.

Reported-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: perterz@infradead.org
Fixes: 5954327548 ("sched/fair: Prepare __update_cpu_load() to handle active tickless")
Link: http://lkml.kernel.org/r/20160115070749.GA1914@X58A-UD3R
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Byungchul Park 2016-01-15 16:07:49 +09:00 committed by Ingo Molnar
parent 6aa447bcbb
commit 7400d3bbaa
1 changed files with 10 additions and 2 deletions
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12
kernel/sched/fair.c
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@ -4509,9 +4509,17 @@ static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
/* scale is effectively 1 << i now, and >> i divides by scale */
old_load = this_rq->cpu_load[i] - tickless_load;
old_load = this_rq->cpu_load[i];
old_load = decay_load_missed(old_load, pending_updates - 1, i);
old_load += tickless_load;
if (tickless_load) {
old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
/*
* old_load can never be a negative value because a
* decayed tickless_load cannot be greater than the
* original tickless_load.
*/
old_load += tickless_load;
}
new_load = this_load;
/*
* Round up the averaging division if load is increasing. This