Messages in this thread | | | Date | Wed, 7 Oct 2020 18:55:33 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v5 1/2] sched/deadline: optimize sched_dl_global_validate() |
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On Wed, Oct 07, 2020 at 11:12:29PM +0800, Peng Liu wrote: > +/* Used for dl_bw check and update. */ > +static u32 dl_generation;
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index 28709f6b0975..53477e8b26b0 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -798,6 +798,13 @@ struct root_domain { > */ > cpumask_var_t dlo_mask; > atomic_t dlo_count; > + > + /* > + * Indicate whether a root_domain's dl_bw has been checked or > + * updated. It's monotonously increasing, then wrap around. > + */ > + u32 visit_gen; > + > struct dl_bw dl_bw; > struct cpudl cpudl; > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index dd7770226086..90f3e5558fa2 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -516,6 +516,7 @@ static int init_rootdomain(struct root_domain *rd) > init_irq_work(&rd->rto_push_work, rto_push_irq_work_func); > #endif > > + rd->visit_gen = 0; > init_dl_bw(&rd->dl_bw); > if (cpudl_init(&rd->cpudl) != 0) > goto free_rto_mask;
I'm fairly sure I made the generation a u64, the above is susceptible to a false positive due to wrap-around.
Increase the generation to -1, create a new root domain, then the next generation is 0 and we'll skip the new domain, even though it should be updated.
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