* Matthias Kaehlcke <m...@chromium.org> wrote:
> The definition of sysctl_sched_migration_cost, sysctl_sched_nr_migrate
> and sysctl_sched_time_avg includes the attribute const_debug. This
> attribute is not part of the extern declaration of these variables in
> include/linux/sched/sysctl.h, as a result clang generates warnings like
> this:
>
> kernel/sched/sched.h:1618:33: warning: section attribute is specified on
> redeclared variable [-Wsection]
> extern const_debug unsigned int sysctl_sched_time_avg;
> ^
> ./include/linux/sched/sysctl.h:42:21: note: previous declaration is here
> extern unsigned int sysctl_sched_time_avg;
>
> The header only declares the variables when CONFIG_SCHED_DEBUG is defined,
> therefore it is not necessary to duplicate the definition of const_debug.
> Instead we can use the attribute __read_mostly, which is the expansion of
> const_debug when CONFIG_SCHED_DEBUG is set.
>
> Signed-off-by: Matthias Kaehlcke <m...@chromium.org>
> Reviewed-by: Nick Desaulniers <nick.desaulni...@gmail.com>
> ---
> Changes in v2:
> - removed pointless include of linux/static_key.h
> - added Reviewed-by tag
>
> include/linux/sched/sysctl.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
> index 0f5ecd4d298e..d34c823f3d36 100644
> --- a/include/linux/sched/sysctl.h
> +++ b/include/linux/sched/sysctl.h
> @@ -37,9 +37,9 @@ extern unsigned int sysctl_numa_balancing_scan_period_max;
> extern unsigned int sysctl_numa_balancing_scan_size;
>
> #ifdef CONFIG_SCHED_DEBUG
> -extern unsigned int sysctl_sched_migration_cost;
> -extern unsigned int sysctl_sched_nr_migrate;
> -extern unsigned int sysctl_sched_time_avg;
> +extern __read_mostly unsigned int sysctl_sched_migration_cost;
> +extern __read_mostly unsigned int sysctl_sched_nr_migrate;
> +extern __read_mostly unsigned int sysctl_sched_time_avg;
So I hate this change, because it pointlessly duplicates an attribute that
should
only matter at the definition site. The Clang warning:
> kernel/sched/sched.h:1618:33: warning: section attribute is specified on
> redeclared variable [-Wsection]
suggests that the -Wsection warning can be turned off. The Clang build should
probably do that.
Thanks,
Ingo
