4.5-stable review patch. If anyone has any objections, please let me know.
------------------ From: Byungchul Park <[email protected]> commit 7400d3bbaa229eb8e7631d28fb34afd7cd2c96ff upstream. decay_load_missed() cannot handle nagative values, so we need to prevent using the function with a negative value. Reported-by: Dietmar Eggemann <[email protected]> Signed-off-by: Byungchul Park <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Chris Metcalf <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Luiz Capitulino <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Paul E . McKenney <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Fixes: 59543275488d ("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 <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- kernel/sched/fair.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4459,9 +4459,17 @@ static void __update_cpu_load(struct rq /* 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
