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    Subject[PATCH 10/30] sched: Add @reason to sched_class->rq_{on|off}line()
    Date
    ->rq_{on|off}line are called either during CPU hotplug or cpuset partition
    updates. A planned BPF extensible sched_class wants to tell the BPF
    scheduler progs about CPU hotplug events in a way that's synchronized with
    rq state changes.

    As the BPF scheduler progs aren't necessarily affected by cpuset partition
    updates, we need a way to distinguish the two types of events. Let's add an
    argument to tell them apart.

    v2: Patch description updated to detail the expected use.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    Reviewed-by: David Vernet <dvernet@meta.com>
    Acked-by: Josh Don <joshdon@google.com>
    Acked-by: Hao Luo <haoluo@google.com>
    Acked-by: Barret Rhoden <brho@google.com>
    ---
    kernel/sched/core.c | 12 ++++++------
    kernel/sched/deadline.c | 4 ++--
    kernel/sched/fair.c | 4 ++--
    kernel/sched/rt.c | 4 ++--
    kernel/sched/sched.h | 13 +++++++++----
    kernel/sched/topology.c | 4 ++--
    6 files changed, 23 insertions(+), 18 deletions(-)

    diff --git a/kernel/sched/core.c b/kernel/sched/core.c
    index 729de63ee6ec..6447f10ecd44 100644
    --- a/kernel/sched/core.c
    +++ b/kernel/sched/core.c
    @@ -9355,7 +9355,7 @@ static inline void balance_hotplug_wait(void)

    #endif /* CONFIG_HOTPLUG_CPU */

    -void set_rq_online(struct rq *rq)
    +void set_rq_online(struct rq *rq, enum rq_onoff_reason reason)
    {
    if (!rq->online) {
    const struct sched_class *class;
    @@ -9365,19 +9365,19 @@ void set_rq_online(struct rq *rq)

    for_each_class(class) {
    if (class->rq_online)
    - class->rq_online(rq);
    + class->rq_online(rq, reason);
    }
    }
    }

    -void set_rq_offline(struct rq *rq)
    +void set_rq_offline(struct rq *rq, enum rq_onoff_reason reason)
    {
    if (rq->online) {
    const struct sched_class *class;

    for_each_class(class) {
    if (class->rq_offline)
    - class->rq_offline(rq);
    + class->rq_offline(rq, reason);
    }

    cpumask_clear_cpu(rq->cpu, rq->rd->online);
    @@ -9473,7 +9473,7 @@ int sched_cpu_activate(unsigned int cpu)
    rq_lock_irqsave(rq, &rf);
    if (rq->rd) {
    BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
    - set_rq_online(rq);
    + set_rq_online(rq, RQ_ONOFF_HOTPLUG);
    }
    rq_unlock_irqrestore(rq, &rf);

    @@ -9518,7 +9518,7 @@ int sched_cpu_deactivate(unsigned int cpu)
    if (rq->rd) {
    update_rq_clock(rq);
    BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
    - set_rq_offline(rq);
    + set_rq_offline(rq, RQ_ONOFF_HOTPLUG);
    }
    rq_unlock_irqrestore(rq, &rf);

    diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
    index 0d97d54276cc..f264814e0513 100644
    --- a/kernel/sched/deadline.c
    +++ b/kernel/sched/deadline.c
    @@ -2518,7 +2518,7 @@ static void set_cpus_allowed_dl(struct task_struct *p,
    }

    /* Assumes rq->lock is held */
    -static void rq_online_dl(struct rq *rq)
    +static void rq_online_dl(struct rq *rq, enum rq_onoff_reason reason)
    {
    if (rq->dl.overloaded)
    dl_set_overload(rq);
    @@ -2529,7 +2529,7 @@ static void rq_online_dl(struct rq *rq)
    }

    /* Assumes rq->lock is held */
    -static void rq_offline_dl(struct rq *rq)
    +static void rq_offline_dl(struct rq *rq, enum rq_onoff_reason reason)
    {
    if (rq->dl.overloaded)
    dl_clear_overload(rq);
    diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
    index fbedf99ed953..b4db8943ed8b 100644
    --- a/kernel/sched/fair.c
    +++ b/kernel/sched/fair.c
    @@ -11673,14 +11673,14 @@ void trigger_load_balance(struct rq *rq)
    nohz_balancer_kick(rq);
    }

    -static void rq_online_fair(struct rq *rq)
    +static void rq_online_fair(struct rq *rq, enum rq_onoff_reason reason)
    {
    update_sysctl();

    update_runtime_enabled(rq);
    }

    -static void rq_offline_fair(struct rq *rq)
    +static void rq_offline_fair(struct rq *rq, enum rq_onoff_reason reason)
    {
    update_sysctl();

    diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
    index ed2a47e4ddae..0fb7ee087669 100644
    --- a/kernel/sched/rt.c
    +++ b/kernel/sched/rt.c
    @@ -2470,7 +2470,7 @@ static void task_woken_rt(struct rq *rq, struct task_struct *p)
    }

    /* Assumes rq->lock is held */
    -static void rq_online_rt(struct rq *rq)
    +static void rq_online_rt(struct rq *rq, enum rq_onoff_reason reason)
    {
    if (rq->rt.overloaded)
    rt_set_overload(rq);
    @@ -2481,7 +2481,7 @@ static void rq_online_rt(struct rq *rq)
    }

    /* Assumes rq->lock is held */
    -static void rq_offline_rt(struct rq *rq)
    +static void rq_offline_rt(struct rq *rq, enum rq_onoff_reason reason)
    {
    if (rq->rt.overloaded)
    rt_clear_overload(rq);
    diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
    index dd567eb7881a..cc1163b15aa0 100644
    --- a/kernel/sched/sched.h
    +++ b/kernel/sched/sched.h
    @@ -2180,6 +2180,11 @@ extern const u32 sched_prio_to_wmult[40];

    #define RETRY_TASK ((void *)-1UL)

    +enum rq_onoff_reason {
    + RQ_ONOFF_HOTPLUG, /* CPU is going on/offline */
    + RQ_ONOFF_TOPOLOGY, /* sched domain topology update */
    +};
    +
    struct affinity_context {
    const struct cpumask *new_mask;
    struct cpumask *user_mask;
    @@ -2216,8 +2221,8 @@ struct sched_class {

    void (*set_cpus_allowed)(struct task_struct *p, struct affinity_context *ctx);

    - void (*rq_online)(struct rq *rq);
    - void (*rq_offline)(struct rq *rq);
    + void (*rq_online)(struct rq *rq, enum rq_onoff_reason reason);
    + void (*rq_offline)(struct rq *rq, enum rq_onoff_reason reason);

    struct rq *(*find_lock_rq)(struct task_struct *p, struct rq *rq);
    #endif
    @@ -2782,8 +2787,8 @@ static inline void double_rq_unlock(struct rq *rq1, struct rq *rq2)
    raw_spin_rq_unlock(rq1);
    }

    -extern void set_rq_online (struct rq *rq);
    -extern void set_rq_offline(struct rq *rq);
    +extern void set_rq_online (struct rq *rq, enum rq_onoff_reason reason);
    +extern void set_rq_offline(struct rq *rq, enum rq_onoff_reason reason);
    extern bool sched_smp_initialized;

    #else /* CONFIG_SMP */
    diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
    index 8739c2a5a54e..0e859bea1cb6 100644
    --- a/kernel/sched/topology.c
    +++ b/kernel/sched/topology.c
    @@ -493,7 +493,7 @@ void rq_attach_root(struct rq *rq, struct root_domain *rd)
    old_rd = rq->rd;

    if (cpumask_test_cpu(rq->cpu, old_rd->online))
    - set_rq_offline(rq);
    + set_rq_offline(rq, RQ_ONOFF_TOPOLOGY);

    cpumask_clear_cpu(rq->cpu, old_rd->span);

    @@ -511,7 +511,7 @@ void rq_attach_root(struct rq *rq, struct root_domain *rd)

    cpumask_set_cpu(rq->cpu, rd->span);
    if (cpumask_test_cpu(rq->cpu, cpu_active_mask))
    - set_rq_online(rq);
    + set_rq_online(rq, RQ_ONOFF_TOPOLOGY);

    raw_spin_rq_unlock_irqrestore(rq, flags);

    --
    2.39.1
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