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    Subject[PATCH 5.9 637/757] sched/features: Fix !CONFIG_JUMP_LABEL case
    Date
    From: Juri Lelli <juri.lelli@redhat.com>

    [ Upstream commit a73f863af4ce9730795eab7097fb2102e6854365 ]

    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=y 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).

    Fix CONFIG_SCHED_DEBUG=y 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 <bristot@redhat.com>
    Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
    Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Acked-by: Patrick Bellasi <patrick.bellasi@matbug.net>
    Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
    Link: https://lore.kernel.org/r/20201013053114.160628-1-juri.lelli@redhat.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 2d95dc3f46444..b1e0da56abcac 100644
    --- a/kernel/sched/core.c
    +++ b/kernel/sched/core.c
    @@ -43,7 +43,7 @@ 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 28709f6b0975c..8d1ca65db3b0d 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;
    --
    2.25.1


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