From 7ed735c33104f3c6194fbc67e3a8b6e64ae84ad1 Mon Sep 17 00:00:00 2001 From: Vincent Guittot Date: Wed, 4 Dec 2019 19:21:40 +0100 Subject: sched/fair: Fix find_idlest_group() to handle CPU affinity Because of CPU affinity, the local group can be skipped which breaks the assumption that statistics are always collected for local group. With uninitialized local_sgs, the comparison is meaningless and the behavior unpredictable. This can even end up to use local pointer which is to NULL in this case. If the local group has been skipped because of CPU affinity, we return the idlest group. Fixes: 57abff067a08 ("sched/fair: Rework find_idlest_group()") Reported-by: John Stultz Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Tested-by: John Stultz Cc: rostedt@goodmis.org Cc: valentin.schneider@arm.com Cc: mingo@redhat.com Cc: mgorman@suse.de Cc: juri.lelli@redhat.com Cc: dietmar.eggemann@arm.com Cc: bsegall@google.com Cc: qais.yousef@arm.com Link: https://lkml.kernel.org/r/1575483700-22153-1-git-send-email-vincent.guittot@linaro.org --- kernel/sched/fair.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'kernel') diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 08a233e97a01..146b6c83633f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8417,6 +8417,10 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, if (!idlest) return NULL; + /* The local group has been skipped because of CPU affinity */ + if (!local) + return idlest; + /* * If the local group is idler than the selected idlest group * don't try and push the task. -- cgit v1.2.3