| Message ID | 1593065595-17794-1-git-send-email-snimmala@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Revert "sched/deadline: Remove cpu_active_mask from cpudl_find()" | expand |
Hi, On 24/06/20 23:13, Sai Harshini Nimmala wrote: > The original commit 9659e1ee removes checking the cpu_active_mask > while finding the best cpu to place a deadline task, citing the reason that > this mask rarely changes and removing the check will give performance > gains. > However, on hotplugging, the cpu dying path has a brief duration between > the CPUHP_TEARDOWN_CPU and CPUHP_AP_SCHED_STARTING hotplug states where > the DL task can be scheduled on this cpu because the corresponding cpu > bit in cpu->free_cpus has not been cleared yet. Without the > cpu_active_mask check we could end up putting a DL task on such cpus > leading to a BUG. > The cpu_active_mask will be updated promptly before either of these > states and will provide a more accurate check for the use case above. > > Signed-off-by: Puja Gupta <pujag@codeaurora.org> > Signed-off-by: Sai Harshini Nimmala <snimmala@codeaurora.org> > --- > kernel/sched/cpudeadline.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c > index 5cc4012..0346837 100644 > --- a/kernel/sched/cpudeadline.c > +++ b/kernel/sched/cpudeadline.c > @@ -120,7 +120,8 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, > const struct sched_dl_entity *dl_se = &p->dl; > > if (later_mask && > - cpumask_and(later_mask, cp->free_cpus, p->cpus_ptr)) { > + cpumask_and(later_mask, cp->free_cpus, p->cpus_ptr) && > + cpumask_and(later_mask, later_mask, cpu_active_mask)) { > return 1; > } else { > int best_cpu = cpudl_maximum(cp); So, I believe the patch you want to revert only removed the condition above. > @@ -128,6 +129,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, > WARN_ON(best_cpu != -1 && !cpu_present(best_cpu)); > > if (cpumask_test_cpu(best_cpu, p->cpus_ptr) && > + cpumask_test_cpu(best_cpu, cpu_active_mask) && > dl_time_before(dl_se->deadline, cp->elements[0].dl)) { > if (later_mask) > cpumask_set_cpu(best_cpu, later_mask); Did you actually experience issues with this second part as well? I'm thinking the WARN_ON should have fired in that case, no? Thanks, Juri
diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c index 5cc4012..0346837 100644 --- a/kernel/sched/cpudeadline.c +++ b/kernel/sched/cpudeadline.c @@ -120,7 +120,8 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, const struct sched_dl_entity *dl_se = &p->dl; if (later_mask && - cpumask_and(later_mask, cp->free_cpus, p->cpus_ptr)) { + cpumask_and(later_mask, cp->free_cpus, p->cpus_ptr) && + cpumask_and(later_mask, later_mask, cpu_active_mask)) { return 1; } else { int best_cpu = cpudl_maximum(cp); @@ -128,6 +129,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, WARN_ON(best_cpu != -1 && !cpu_present(best_cpu)); if (cpumask_test_cpu(best_cpu, p->cpus_ptr) && + cpumask_test_cpu(best_cpu, cpu_active_mask) && dl_time_before(dl_se->deadline, cp->elements[0].dl)) { if (later_mask) cpumask_set_cpu(best_cpu, later_mask);