Re: [PATCH 3/5] sched/deadline: Fix wrong cpudl_find() in check_preempt_equal_dl()

Peter Zijlstra
2015-01-27T12:48:23Z

On Mon, Jan 19, 2015 at 04:49:38AM +0000, Xunlei Pang wrote:
> +++ b/kernel/sched/deadline.c
> @@ -943,14 +943,23 @@ out:
> return cpu;
> }
>
> +static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
> +
> static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
> {
> + struct cpumask *later_mask =
> + this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
> +
> + /* Make sure the mask is initialized first */
> + if (unlikely(!later_mask))
> + return;
> +
> /*
> * Current can't be migrated, useless to reschedule,
> * let's hope p can move out.
> */
> if (rq->curr->nr_cpus_allowed == 1 ||
> - cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)
> + cpudl_find(&rq->rd->cpudl, rq->curr, later_mask) == -1)
> return;
>
> /*

But but, should you not put something in that mask before you use it?