On Tue, Oct 13, 2020 at 07:31:14 +0200, Juri Lelli <juri.le...@redhat.com>
wrote...
> Commit 765cc3a4b224e ("sched/core: Optimize sched_feat() for
> !CONFIG_SCHED_DEBUG builds") made sched features static for
> !CONFIG_SCHED_DEBUG configurations, but overlooked the CONFIG_
> SCHED_DEBUG enabled and !CONFIG_JUMP_LABEL cases. For the latter echoing
> changes to /sys/kernel/debug/sched_features has the nasty effect of
> effectively changing what sched_features reports, but without actually
> changing the scheduler behaviour (since different translation units get
> different sysctl_sched_features).
Hops, yes, I think I missed to properly check that config :/
Good spot!
> Fix CONFIG_SCHED_DEBUG and !CONFIG_JUMP_LABEL configurations by properly
> restructuring ifdefs.
>
> Fixes: 765cc3a4b224e ("sched/core: Optimize sched_feat() for
> !CONFIG_SCHED_DEBUG builds")
> Co-developed-by: Daniel Bristot de Oliveira <bris...@redhat.com>
> Signed-off-by: Daniel Bristot de Oliveira <bris...@redhat.com>
> Signed-off-by: Juri Lelli <juri.le...@redhat.com>
(did you get some wrong formatting for the changelog above?)
> ---
> v1->v2
> - use CONFIG_JUMP_LABEL (and not the old HAVE_JUMP_LABEL) [Valentin]
> ---
> kernel/sched/core.c | 2 +-
> kernel/sched/sched.h | 13 ++++++++++---
> 2 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 3dc415f58bd7..a7949e3ed7e7 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -44,7 +44,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
>
> DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
>
> -#if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_JUMP_LABEL)
> +#ifdef CONFIG_SCHED_DEBUG
> /*
> * Debugging: various feature bits
> *
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 28709f6b0975..8d1ca65db3b0 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1629,7 +1629,7 @@ enum {
>
> #undef SCHED_FEAT
>
> -#if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_JUMP_LABEL)
> +#ifdef CONFIG_SCHED_DEBUG
>
> /*
> * To support run-time toggling of sched features, all the translation units
> @@ -1637,6 +1637,7 @@ enum {
> */
> extern const_debug unsigned int sysctl_sched_features;
>
> +#ifdef CONFIG_JUMP_LABEL
> #define SCHED_FEAT(name, enabled) \
> static __always_inline bool static_branch_##name(struct static_key *key) \
> { \
> @@ -1649,7 +1650,13 @@ static __always_inline bool
> static_branch_##name(struct static_key *key) \
> extern struct static_key sched_feat_keys[__SCHED_FEAT_NR];
> #define sched_feat(x) (static_branch_##x(&sched_feat_keys[__SCHED_FEAT_##x]))
>
> -#else /* !(SCHED_DEBUG && CONFIG_JUMP_LABEL) */
> +#else /* !CONFIG_JUMP_LABEL */
> +
> +#define sched_feat(x) (sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
> +
> +#endif /* CONFIG_JUMP_LABEL */
> +
> +#else /* !SCHED_DEBUG */
>
> /*
> * Each translation unit has its own copy of sysctl_sched_features to allow
> @@ -1665,7 +1672,7 @@ static const_debug __maybe_unused unsigned int
> sysctl_sched_features =
>
> #define sched_feat(x) !!(sysctl_sched_features & (1UL << __SCHED_FEAT_##x))
>
> -#endif /* SCHED_DEBUG && CONFIG_JUMP_LABEL */
> +#endif /* SCHED_DEBUG */
>
> extern struct static_key_false sched_numa_balancing;
> extern struct static_key_false sched_schedstats;
