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Message-ID: <xhsmhfsgc4vhg.mognet@vschneid.remote.csb> Date: Tue, 27 Sep 2022 17:45:15 +0100 From: Valentin Schneider <vschneid@...hat.com> To: Yury Norov <yury.norov@...il.com> Cc: netdev@...r.kernel.org, linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org, Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Rasmus Villemoes <linux@...musvillemoes.dk>, Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, Mel Gorman <mgorman@...e.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Heiko Carstens <hca@...ux.ibm.com>, Tony Luck <tony.luck@...el.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>, Gal Pressman <gal@...dia.com>, Tariq Toukan <tariqt@...dia.com>, Jesse Brandeburg <jesse.brandeburg@...el.com> Subject: Re: [PATCH v4 5/7] sched/topology: Introduce sched_numa_hop_mask() On 25/09/22 11:05, Yury Norov wrote: > On Fri, Sep 23, 2022 at 04:55:40PM +0100, Valentin Schneider wrote: >> +const struct cpumask *sched_numa_hop_mask(int node, int hops) >> +{ >> + struct cpumask ***masks = rcu_dereference(sched_domains_numa_masks); >> + >> + if (node == NUMA_NO_NODE && !hops) >> + return cpu_online_mask; >> + >> + if (node >= nr_node_ids || hops >= sched_domains_numa_levels) >> + return ERR_PTR(-EINVAL); > > This looks like a sanity check. If so, it should go before the snippet > above, so that client code would behave consistently. > nr_node_ids is unsigned, so -1 >= nr_node_ids is true. >> + >> + if (!masks) >> + return NULL; > > In (node == NUMA_NO_NODE && !hops) case you return online cpus. Here > you return NULL just to convert it to cpu_online_mask in the caller. > This looks inconsistent. So, together with the above comment, this > makes me feel that you'd do it like this: > > const struct cpumask *sched_numa_hop_mask(int node, int hops) > { > struct cpumask ***masks; > > if (node >= nr_node_ids || hops >= sched_domains_numa_levels) > { > #ifdef CONFIG_SCHED_DEBUG > pr_err(...); > #endif > return ERR_PTR(-EINVAL); > } > > if (node == NUMA_NO_NODE && !hops) > return cpu_online_mask; /* or NULL */ > > masks = rcu_dereference(sched_domains_numa_masks); > if (!masks) > return cpu_online_mask; /* or NULL */ > > return masks[hops][node]; > } If we're being pedantic, sched_numa_hop_mask() shouldn't return cpu_online_mask in those cases, but that was the least horrible option I found to get something sensible for the NUMA_NO_NODE / !CONFIG_NUMA case. I might be able to better handle this with your suggestion of having a mask iterator.
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