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Date: Mon, 18 Sep 2017 11:15:34 -0400 From: Steven Rostedt <rostedt@...dmis.org> To: Byungchul Park <byungchul.park@....com> Cc: peterz@...radead.org, mingo@...nel.org, linux-kernel@...r.kernel.org, juri.lelli@...il.com, kernel-team@....com Subject: Re: [PATCH v2 2/2] sched/deadline: Initialize cp->elements[].cpu to an invalid value On Thu, 14 Sep 2017 10:05:19 +0900 Byungchul Park <byungchul.park@....com> wrote: > Currently, migrating tasks to cpu0 unconditionally happens when the > heap is empty, since cp->elements[].cpu was initialized to 0(=cpu0). > We have to distinguish between the empty case and cpu0 to avoid the > unnecessary migrantions. Therefore, it has to return an invalid value > e.i. -1 in that case. > Looks good to me. Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org> Peter, you back from LA? Can you review these and send them to Ingo? -- Steve > Signed-off-by: Byungchul Park <byungchul.park@....com> > --- > kernel/sched/cpudeadline.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c > index 9f02035..bcf903f 100644 > --- a/kernel/sched/cpudeadline.c > +++ b/kernel/sched/cpudeadline.c > @@ -138,6 +138,12 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, > int best_cpu = cpudl_maximum_cpu(cp); > WARN_ON(best_cpu != -1 && !cpu_present(best_cpu)); > > + /* > + * The heap tree is empry for now, just return. > + */ > + if (best_cpu == -1) > + return 0; > + > if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) && > dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) { > if (later_mask) > @@ -265,8 +271,10 @@ int cpudl_init(struct cpudl *cp) > return -ENOMEM; > } > > - for_each_possible_cpu(i) > + for_each_possible_cpu(i) { > + cp->elements[i].cpu = -1; > cp->elements[i].idx = IDX_INVALID; > + } > > return 0; > }
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