Hierarchy could be already throttled at this point. Throttled next buddy could trigger null pointer dereference in pick_next_task_fair(). Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> Cc: Stable <stable@xxxxxxxxxxxxxxx> # v3.2+ --- kernel/sched/fair.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index fe809fe169d2..3c6b038cb734 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4519,15 +4519,14 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) /* Don't dequeue parent if it has other entities besides us */ if (cfs_rq->load.weight) { + /* avoid re-evaluating load for this entity */ + se = parent_entity(se); /* * Bias pick_next to pick a task from this cfs_rq, as * p is sleeping when it is within its sched_slice. */ - if (task_sleep && parent_entity(se)) - set_next_buddy(parent_entity(se)); - - /* avoid re-evaluating load for this entity */ - se = parent_entity(se); + if (task_sleep && se && !throttled_hierarchy(cfs_rq)) + set_next_buddy(se); break; } flags |= DEQUEUE_SLEEP; -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html