Commit a761ae85 authored Jun 08, 2017 by Pavankumar Kondeti

sched: Fix the bug in select_best_cpu() that returns -1 as target_cpu

select_best_cpu() has previous CPU's cluster bias which overrides
the best_cpu with best_sibling_cpu when the power cost is same.
When the power table is configured incorrectly or static_cpu_pwr_cost/
static_cluster_pwr_cost tunables are set to a large value, the
power_cost() for all candidate CPUs can return INT_MAX. So the
stats.min_cost is never changed from it's initial value i.e INT_MAX.

In the above scenario, we find stats.best_cpu >= 0 && stats.min_cost =
stats.best_sibling_cpu_cost = INT_MAX && stats.best_sibling_cpu_cost = -1
and replace best_cpu with best_sibling_cpu i.e -1.

Change-Id: I09829e278e41daaaff959428ff50927aba29104c
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>

parent 9725c4d9

kernel/sched/fair.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -3240,7 +3240,8 @@ retry:
		sbc_flag \|= SBC_FLAG_IDLE_LEAST_LOADED;
		}
		} else if (stats.best_cpu >= 0) {
		if (stats.best_cpu != task_cpu(p) &&
		if (stats.best_sibling_cpu >= 0 &&
		stats.best_cpu != task_cpu(p) &&
		stats.min_cost == stats.best_sibling_cpu_cost) {
		stats.best_cpu = stats.best_sibling_cpu;
		sbc_flag \|= SBC_FLAG_BEST_SIBLING;