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Date: Mon, 25 Feb 2019 13:11:08 -0800
From: "Paul E. McKenney" <paulmck@...ux.ibm.com>
To: "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc: linux-kernel@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
Christian Brauner <christian@...uner.io>,
Daniel Borkmann <daniel@...earbox.net>,
David Ahern <dsahern@...il.com>,
"David S. Miller" <davem@...emloft.net>,
Ingo Molnar <mingo@...hat.com>,
Jakub Kicinski <jakub.kicinski@...ronome.com>,
Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
Jesper Dangaard Brouer <hawk@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
Josh Triplett <josh@...htriplett.org>, keescook@...omium.org,
kernel-hardening@...ts.openwall.com, kernel-team@...roid.com,
Kirill Tkhai <ktkhai@...tuozzo.com>,
Lai Jiangshan <jiangshanlai@...il.com>,
Martin KaFai Lau <kafai@...com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
netdev@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
Quentin Perret <quentin.perret@....com>, rcu@...r.kernel.org,
Song Liu <songliubraving@...com>, Steven Rostedt <rostedt@...dmis.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
xdp-newbies@...r.kernel.org, Yonghong Song <yhs@...com>
Subject: Re: [PATCH v2 4/6] sched_domain: Annotate RCU pointers properly
On Sat, Feb 23, 2019 at 01:34:32AM -0500, Joel Fernandes (Google) wrote:
> The scheduler uses RCU API in various places to access sched_domain
> pointers. These cause sparse errors as below.
>
> Many new errors show up because of an annotation check I added to
> rcu_assign_pointer(). Let us annotate the pointers correctly which also
> will help sparse catch any potential future bugs.
>
> This fixes the following sparse errors:
>
> rt.c:1681:9: error: incompatible types in comparison expression
> deadline.c:1904:9: error: incompatible types in comparison expression
> core.c:519:9: error: incompatible types in comparison expression
> core.c:1634:17: error: incompatible types in comparison expression
> fair.c:6193:14: error: incompatible types in comparison expression
> fair.c:9883:22: error: incompatible types in comparison expression
> fair.c:9897:9: error: incompatible types in comparison expression
> sched.h:1287:9: error: incompatible types in comparison expression
> topology.c:612:9: error: incompatible types in comparison expression
> topology.c:615:9: error: incompatible types in comparison expression
> sched.h:1300:9: error: incompatible types in comparison expression
> topology.c:618:9: error: incompatible types in comparison expression
> sched.h:1287:9: error: incompatible types in comparison expression
> topology.c:621:9: error: incompatible types in comparison expression
> sched.h:1300:9: error: incompatible types in comparison expression
> topology.c:624:9: error: incompatible types in comparison expression
> topology.c:671:9: error: incompatible types in comparison expression
> stats.c:45:17: error: incompatible types in comparison expression
> fair.c:5998:15: error: incompatible types in comparison expression
> fair.c:5989:15: error: incompatible types in comparison expression
> fair.c:5998:15: error: incompatible types in comparison expression
> fair.c:5989:15: error: incompatible types in comparison expression
> fair.c:6120:19: error: incompatible types in comparison expression
> fair.c:6506:14: error: incompatible types in comparison expression
> fair.c:6515:14: error: incompatible types in comparison expression
> fair.c:6623:9: error: incompatible types in comparison expression
> fair.c:5970:17: error: incompatible types in comparison expression
> fair.c:8642:21: error: incompatible types in comparison expression
> fair.c:9253:9: error: incompatible types in comparison expression
> fair.c:9331:9: error: incompatible types in comparison expression
> fair.c:9519:15: error: incompatible types in comparison expression
> fair.c:9533:14: error: incompatible types in comparison expression
> fair.c:9542:14: error: incompatible types in comparison expression
> fair.c:9567:14: error: incompatible types in comparison expression
> fair.c:9597:14: error: incompatible types in comparison expression
> fair.c:9421:16: error: incompatible types in comparison expression
> fair.c:9421:16: error: incompatible types in comparison expression
>
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
>From an RCU perspective:
Reviewed-by: Paul E. McKenney <paulmck@...ux.ibm.com>
> ---
> include/linux/sched/topology.h | 4 ++--
> kernel/sched/sched.h | 14 +++++++-------
> kernel/sched/topology.c | 10 +++++-----
> 3 files changed, 14 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
> index c31d3a47a47c..4819c9e01e42 100644
> --- a/include/linux/sched/topology.h
> +++ b/include/linux/sched/topology.h
> @@ -76,8 +76,8 @@ struct sched_domain_shared {
>
> struct sched_domain {
> /* These fields must be setup */
> - struct sched_domain *parent; /* top domain must be null terminated */
> - struct sched_domain *child; /* bottom domain must be null terminated */
> + struct sched_domain __rcu *parent; /* top domain must be null terminated */
> + struct sched_domain __rcu *child; /* bottom domain must be null terminated */
> struct sched_group *groups; /* the balancing groups of the domain */
> unsigned long min_interval; /* Minimum balance interval ms */
> unsigned long max_interval; /* Maximum balance interval ms */
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 2ab545d40381..ca6a79f57e7a 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -866,8 +866,8 @@ struct rq {
> atomic_t nr_iowait;
>
> #ifdef CONFIG_SMP
> - struct root_domain *rd;
> - struct sched_domain *sd;
> + struct root_domain *rd;
> + struct sched_domain __rcu *sd;
>
> unsigned long cpu_capacity;
> unsigned long cpu_capacity_orig;
> @@ -1305,13 +1305,13 @@ static inline struct sched_domain *lowest_flag_domain(int cpu, int flag)
> return sd;
> }
>
> -DECLARE_PER_CPU(struct sched_domain *, sd_llc);
> +DECLARE_PER_CPU(struct sched_domain __rcu *, sd_llc);
> DECLARE_PER_CPU(int, sd_llc_size);
> DECLARE_PER_CPU(int, sd_llc_id);
> -DECLARE_PER_CPU(struct sched_domain_shared *, sd_llc_shared);
> -DECLARE_PER_CPU(struct sched_domain *, sd_numa);
> -DECLARE_PER_CPU(struct sched_domain *, sd_asym_packing);
> -DECLARE_PER_CPU(struct sched_domain *, sd_asym_cpucapacity);
> +DECLARE_PER_CPU(struct sched_domain_shared __rcu *, sd_llc_shared);
> +DECLARE_PER_CPU(struct sched_domain __rcu *, sd_numa);
> +DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing);
> +DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity);
> extern struct static_key_false sched_asym_cpucapacity;
>
> struct sched_group_capacity {
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index 3f35ba1d8fde..0844ee757dad 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -586,13 +586,13 @@ static void destroy_sched_domains(struct sched_domain *sd)
> * the cpumask of the domain), this allows us to quickly tell if
> * two CPUs are in the same cache domain, see cpus_share_cache().
> */
> -DEFINE_PER_CPU(struct sched_domain *, sd_llc);
> +DEFINE_PER_CPU(struct sched_domain __rcu *, sd_llc);
> DEFINE_PER_CPU(int, sd_llc_size);
> DEFINE_PER_CPU(int, sd_llc_id);
> -DEFINE_PER_CPU(struct sched_domain_shared *, sd_llc_shared);
> -DEFINE_PER_CPU(struct sched_domain *, sd_numa);
> -DEFINE_PER_CPU(struct sched_domain *, sd_asym_packing);
> -DEFINE_PER_CPU(struct sched_domain *, sd_asym_cpucapacity);
> +DEFINE_PER_CPU(struct sched_domain_shared __rcu *, sd_llc_shared);
> +DEFINE_PER_CPU(struct sched_domain __rcu *, sd_numa);
> +DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing);
> +DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity);
> DEFINE_STATIC_KEY_FALSE(sched_asym_cpucapacity);
>
> static void update_top_cache_domain(int cpu)
> --
> 2.21.0.rc0.258.g878e2cd30e-goog
>
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