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SubjectRe: [PATCH v2 3/6] sched/cpufreq: Annotate cpufreq_update_util_data pointer with __rcu
On Sat, Feb 23, 2019 at 01:34:31AM -0500, Joel Fernandes (Google) wrote:
> Recently I added an RCU annotation check to rcu_assign_pointer(). All
> pointers assigned to RCU protected data are to be annotated with __rcu
> inorder to be able to use rcu_assign_pointer() similar to checks in
> other RCU APIs.
>
> This resulted in a sparse error: kernel//sched/cpufreq.c:41:9: sparse:
> error: incompatible types in comparison expression (different address
> spaces)
>
> Fix this by annotating cpufreq_update_util_data pointer with __rcu. This
> will also help sparse catch any future RCU misuage bugs.
>
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>

From an RCU perspective:

Reviewed-by: Paul E. McKenney <paulmck@linux.ibm.com>

> ---
> kernel/sched/cpufreq.c | 2 +-
> kernel/sched/sched.h | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/cpufreq.c b/kernel/sched/cpufreq.c
> index 22bd8980f32f..e316ee7bb2e5 100644
> --- a/kernel/sched/cpufreq.c
> +++ b/kernel/sched/cpufreq.c
> @@ -7,7 +7,7 @@
> */
> #include "sched.h"
>
> -DEFINE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);
> +DEFINE_PER_CPU(struct update_util_data __rcu *, cpufreq_update_util_data);
>
> /**
> * cpufreq_add_update_util_hook - Populate the CPU's update_util_data pointer.
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index d04530bf251f..2ab545d40381 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2166,7 +2166,7 @@ static inline u64 irq_time_read(int cpu)
> #endif /* CONFIG_IRQ_TIME_ACCOUNTING */
>
> #ifdef CONFIG_CPU_FREQ
> -DECLARE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);
> +DECLARE_PER_CPU(struct update_util_data __rcu *, cpufreq_update_util_data);
>
> /**
> * cpufreq_update_util - Take a note about CPU utilization changes.
> --
> 2.21.0.rc0.258.g878e2cd30e-goog
>

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