sched_ext: Clean up scx_root usages

- Always cache scx_root into local variable sch before using.

- Don't use scx_root if cached sch is available.

- Wrap !sch test with unlikely().

- Pass @scx into scx_cgroup_init/exit().

No behavior changes intended.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 8ccb5c7ff55c974f911e667f88c656ca58f9c6f9..490506a844d669d210267aa71ddcbb1ab478bc60 100644 (file)
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -2220,20 +2220,20 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
                goto direct;
 
        /* see %SCX_OPS_ENQ_EXITING */
-       if (!(scx_root->ops.flags & SCX_OPS_ENQ_EXITING) &&
+       if (!(sch->ops.flags & SCX_OPS_ENQ_EXITING) &&
            unlikely(p->flags & PF_EXITING)) {
                __scx_add_event(sch, SCX_EV_ENQ_SKIP_EXITING, 1);
                goto local;
        }
 
        /* see %SCX_OPS_ENQ_MIGRATION_DISABLED */
-       if (!(scx_root->ops.flags & SCX_OPS_ENQ_MIGRATION_DISABLED) &&
+       if (!(sch->ops.flags & SCX_OPS_ENQ_MIGRATION_DISABLED) &&
            is_migration_disabled(p)) {
                __scx_add_event(sch, SCX_EV_ENQ_SKIP_MIGRATION_DISABLED, 1);
                goto local;
        }
 
-       if (unlikely(!SCX_HAS_OP(scx_root, enqueue)))
+       if (unlikely(!SCX_HAS_OP(sch, enqueue)))
                goto global;
 
        /* DSQ bypass didn't trigger, enqueue on the BPF scheduler */
@@ -2311,6 +2311,7 @@ static void clr_task_runnable(struct task_struct *p, bool reset_runnable_at)
 
 static void enqueue_task_scx(struct rq *rq, struct task_struct *p, int enq_flags)
 {
+       struct scx_sched *sch = scx_root;
        int sticky_cpu = p->scx.sticky_cpu;
 
        if (enq_flags & ENQUEUE_WAKEUP)
@@ -2340,7 +2341,7 @@ static void enqueue_task_scx(struct rq *rq, struct task_struct *p, int enq_flags
        rq->scx.nr_running++;
        add_nr_running(rq, 1);
 
-       if (SCX_HAS_OP(scx_root, runnable) && !task_on_rq_migrating(p))
+       if (SCX_HAS_OP(sch, runnable) && !task_on_rq_migrating(p))
                SCX_CALL_OP_TASK(SCX_KF_REST, runnable, rq, p, enq_flags);
 
        if (enq_flags & SCX_ENQ_WAKEUP)
@@ -2352,11 +2353,12 @@ out:
 
        if ((enq_flags & SCX_ENQ_CPU_SELECTED) &&
            unlikely(cpu_of(rq) != p->scx.selected_cpu))
-               __scx_add_event(scx_root, SCX_EV_SELECT_CPU_FALLBACK, 1);
+               __scx_add_event(sch, SCX_EV_SELECT_CPU_FALLBACK, 1);
 }
 
 static void ops_dequeue(struct rq *rq, struct task_struct *p, u64 deq_flags)
 {
+       struct scx_sched *sch = scx_root;
        unsigned long opss;
 
        /* dequeue is always temporary, don't reset runnable_at */
@@ -2375,7 +2377,7 @@ static void ops_dequeue(struct rq *rq, struct task_struct *p, u64 deq_flags)
                 */
                BUG();
        case SCX_OPSS_QUEUED:
-               if (SCX_HAS_OP(scx_root, dequeue))
+               if (SCX_HAS_OP(sch, dequeue))
                        SCX_CALL_OP_TASK(SCX_KF_REST, dequeue, rq, p, deq_flags);
 
                if (atomic_long_try_cmpxchg(&p->scx.ops_state, &opss,
@@ -2404,6 +2406,8 @@ static void ops_dequeue(struct rq *rq, struct task_struct *p, u64 deq_flags)
 
 static bool dequeue_task_scx(struct rq *rq, struct task_struct *p, int deq_flags)
 {
+       struct scx_sched *sch = scx_root;
+
        if (!(p->scx.flags & SCX_TASK_QUEUED)) {
                WARN_ON_ONCE(task_runnable(p));
                return true;
@@ -2423,12 +2427,12 @@ static bool dequeue_task_scx(struct rq *rq, struct task_struct *p, int deq_flags
         * information meaningful to the BPF scheduler and can be suppressed by
         * skipping the callbacks if the task is !QUEUED.
         */
-       if (SCX_HAS_OP(scx_root, stopping) && task_current(rq, p)) {
+       if (SCX_HAS_OP(sch, stopping) && task_current(rq, p)) {
                update_curr_scx(rq);
                SCX_CALL_OP_TASK(SCX_KF_REST, stopping, rq, p, false);
        }
 
-       if (SCX_HAS_OP(scx_root, quiescent) && !task_on_rq_migrating(p))
+       if (SCX_HAS_OP(sch, quiescent) && !task_on_rq_migrating(p))
                SCX_CALL_OP_TASK(SCX_KF_REST, quiescent, rq, p, deq_flags);
 
        if (deq_flags & SCX_DEQ_SLEEP)
@@ -2446,9 +2450,10 @@ static bool dequeue_task_scx(struct rq *rq, struct task_struct *p, int deq_flags
 
 static void yield_task_scx(struct rq *rq)
 {
+       struct scx_sched *sch = scx_root;
        struct task_struct *p = rq->curr;
 
-       if (SCX_HAS_OP(scx_root, yield))
+       if (SCX_HAS_OP(sch, yield))
                SCX_CALL_OP_2TASKS_RET(SCX_KF_REST, yield, rq, p, NULL);
        else
                p->scx.slice = 0;
@@ -2456,9 +2461,10 @@ static void yield_task_scx(struct rq *rq)
 
 static bool yield_to_task_scx(struct rq *rq, struct task_struct *to)
 {
+       struct scx_sched *sch = scx_root;
        struct task_struct *from = rq->curr;
 
-       if (SCX_HAS_OP(scx_root, yield))
+       if (SCX_HAS_OP(sch, yield))
                return SCX_CALL_OP_2TASKS_RET(SCX_KF_REST, yield, rq, from, to);
        else
                return false;
@@ -3011,7 +3017,7 @@ static int balance_one(struct rq *rq, struct task_struct *prev)
        rq->scx.flags |= SCX_RQ_IN_BALANCE;
        rq->scx.flags &= ~(SCX_RQ_BAL_PENDING | SCX_RQ_BAL_KEEP);
 
-       if ((scx_root->ops.flags & SCX_OPS_HAS_CPU_PREEMPT) &&
+       if ((sch->ops.flags & SCX_OPS_HAS_CPU_PREEMPT) &&
            unlikely(rq->scx.cpu_released)) {
                /*
                 * If the previous sched_class for the current CPU was not SCX,
@@ -3019,7 +3025,7 @@ static int balance_one(struct rq *rq, struct task_struct *prev)
                 * core. This callback complements ->cpu_release(), which is
                 * emitted in switch_class().
                 */
-               if (SCX_HAS_OP(scx_root, cpu_acquire))
+               if (SCX_HAS_OP(sch, cpu_acquire))
                        SCX_CALL_OP(SCX_KF_REST, cpu_acquire, rq, cpu_of(rq), NULL);
                rq->scx.cpu_released = false;
        }
@@ -3050,7 +3056,7 @@ static int balance_one(struct rq *rq, struct task_struct *prev)
        if (consume_global_dsq(sch, rq))
                goto has_tasks;
 
-       if (unlikely(!SCX_HAS_OP(scx_root, dispatch)) ||
+       if (unlikely(!SCX_HAS_OP(sch, dispatch)) ||
            scx_rq_bypassing(rq) || !scx_rq_online(rq))
                goto no_tasks;
 
@@ -3101,7 +3107,7 @@ no_tasks:
         * %SCX_OPS_ENQ_LAST is in effect.
         */
        if (prev_on_rq &&
-           (!(scx_root->ops.flags & SCX_OPS_ENQ_LAST) || scx_rq_bypassing(rq))) {
+           (!(sch->ops.flags & SCX_OPS_ENQ_LAST) || scx_rq_bypassing(rq))) {
                rq->scx.flags |= SCX_RQ_BAL_KEEP;
                __scx_add_event(sch, SCX_EV_DISPATCH_KEEP_LAST, 1);
                goto has_tasks;
@@ -3176,6 +3182,8 @@ static void process_ddsp_deferred_locals(struct rq *rq)
 
 static void set_next_task_scx(struct rq *rq, struct task_struct *p, bool first)
 {
+       struct scx_sched *sch = scx_root;
+
        if (p->scx.flags & SCX_TASK_QUEUED) {
                /*
                 * Core-sched might decide to execute @p before it is
@@ -3188,7 +3196,7 @@ static void set_next_task_scx(struct rq *rq, struct task_struct *p, bool first)
        p->se.exec_start = rq_clock_task(rq);
 
        /* see dequeue_task_scx() on why we skip when !QUEUED */
-       if (SCX_HAS_OP(scx_root, running) && (p->scx.flags & SCX_TASK_QUEUED))
+       if (SCX_HAS_OP(sch, running) && (p->scx.flags & SCX_TASK_QUEUED))
                SCX_CALL_OP_TASK(SCX_KF_REST, running, rq, p);
 
        clr_task_runnable(p, true);
@@ -3232,6 +3240,7 @@ preempt_reason_from_class(const struct sched_class *class)
 
 static void switch_class(struct rq *rq, struct task_struct *next)
 {
+       struct scx_sched *sch = scx_root;
        const struct sched_class *next_class = next->sched_class;
 
 #ifdef CONFIG_SMP
@@ -3242,7 +3251,7 @@ static void switch_class(struct rq *rq, struct task_struct *next)
         */
        smp_store_release(&rq->scx.pnt_seq, rq->scx.pnt_seq + 1);
 #endif
-       if (!(scx_root->ops.flags & SCX_OPS_HAS_CPU_PREEMPT))
+       if (!(sch->ops.flags & SCX_OPS_HAS_CPU_PREEMPT))
                return;
 
        /*
@@ -3264,7 +3273,7 @@ static void switch_class(struct rq *rq, struct task_struct *next)
         *  next time that balance_scx() is invoked.
         */
        if (!rq->scx.cpu_released) {
-               if (SCX_HAS_OP(scx_root, cpu_release)) {
+               if (SCX_HAS_OP(sch, cpu_release)) {
                        struct scx_cpu_release_args args = {
                                .reason = preempt_reason_from_class(next_class),
                                .task = next,
@@ -3279,10 +3288,11 @@ static void switch_class(struct rq *rq, struct task_struct *next)
 static void put_prev_task_scx(struct rq *rq, struct task_struct *p,
                              struct task_struct *next)
 {
+       struct scx_sched *sch = scx_root;
        update_curr_scx(rq);
 
        /* see dequeue_task_scx() on why we skip when !QUEUED */
-       if (SCX_HAS_OP(scx_root, stopping) && (p->scx.flags & SCX_TASK_QUEUED))
+       if (SCX_HAS_OP(sch, stopping) && (p->scx.flags & SCX_TASK_QUEUED))
                SCX_CALL_OP_TASK(SCX_KF_REST, stopping, rq, p, true);
 
        if (p->scx.flags & SCX_TASK_QUEUED) {
@@ -3306,7 +3316,7 @@ static void put_prev_task_scx(struct rq *rq, struct task_struct *p,
                 * which should trigger an explicit follow-up scheduling event.
                 */
                if (sched_class_above(&ext_sched_class, next->sched_class)) {
-                       WARN_ON_ONCE(!(scx_root->ops.flags & SCX_OPS_ENQ_LAST));
+                       WARN_ON_ONCE(!(sch->ops.flags & SCX_OPS_ENQ_LAST));
                        do_enqueue_task(rq, p, SCX_ENQ_LAST, -1);
                } else {
                        do_enqueue_task(rq, p, 0, -1);
@@ -3381,10 +3391,12 @@ static struct task_struct *pick_task_scx(struct rq *rq)
                }
 
                if (unlikely(!p->scx.slice)) {
-                       if (!scx_rq_bypassing(rq) && !scx_root->warned_zero_slice) {
+                       struct scx_sched *sch = scx_root;
+
+                       if (!scx_rq_bypassing(rq) && !sch->warned_zero_slice) {
                                printk_deferred(KERN_WARNING "sched_ext: %s[%d] has zero slice in %s()\n",
                                                p->comm, p->pid, __func__);
-                               scx_root->warned_zero_slice = true;
+                               sch->warned_zero_slice = true;
                        }
                        refill_task_slice_dfl(p);
                }
@@ -3415,12 +3427,14 @@ static struct task_struct *pick_task_scx(struct rq *rq)
 bool scx_prio_less(const struct task_struct *a, const struct task_struct *b,
                   bool in_fi)
 {
+       struct scx_sched *sch = scx_root;
+
        /*
         * The const qualifiers are dropped from task_struct pointers when
         * calling ops.core_sched_before(). Accesses are controlled by the
         * verifier.
         */
-       if (SCX_HAS_OP(scx_root, core_sched_before) &&
+       if (SCX_HAS_OP(sch, core_sched_before) &&
            !scx_rq_bypassing(task_rq(a)))
                return SCX_CALL_OP_2TASKS_RET(SCX_KF_REST, core_sched_before, NULL,
                                              (struct task_struct *)a,
@@ -3493,6 +3507,8 @@ static void task_woken_scx(struct rq *rq, struct task_struct *p)
 static void set_cpus_allowed_scx(struct task_struct *p,
                                 struct affinity_context *ac)
 {
+       struct scx_sched *sch = scx_root;
+
        set_cpus_allowed_common(p, ac);
 
        /*
@@ -3503,13 +3519,14 @@ static void set_cpus_allowed_scx(struct task_struct *p,
         * Fine-grained memory write control is enforced by BPF making the const
         * designation pointless. Cast it away when calling the operation.
         */
-       if (SCX_HAS_OP(scx_root, set_cpumask))
+       if (SCX_HAS_OP(sch, set_cpumask))
                SCX_CALL_OP_TASK(SCX_KF_REST, set_cpumask, NULL,
                                 p, (struct cpumask *)p->cpus_ptr);
 }
 
 static void handle_hotplug(struct rq *rq, bool online)
 {
+       struct scx_sched *sch = scx_root;
        int cpu = cpu_of(rq);
 
        atomic_long_inc(&scx_hotplug_seq);
@@ -3519,15 +3536,15 @@ static void handle_hotplug(struct rq *rq, bool online)
         * stable here. Note that we can't depend on scx_enabled() test as the
         * hotplug ops need to be enabled before __scx_enabled is set.
         */
-       if (!scx_root)
+       if (unlikely(!sch))
                return;
 
        if (scx_enabled())
-               scx_idle_update_selcpu_topology(&scx_root->ops);
+               scx_idle_update_selcpu_topology(&sch->ops);
 
-       if (online && SCX_HAS_OP(scx_root, cpu_online))
+       if (online && SCX_HAS_OP(sch, cpu_online))
                SCX_CALL_OP(SCX_KF_UNLOCKED, cpu_online, NULL, cpu);
-       else if (!online && SCX_HAS_OP(scx_root, cpu_offline))
+       else if (!online && SCX_HAS_OP(sch, cpu_offline))
                SCX_CALL_OP(SCX_KF_UNLOCKED, cpu_offline, NULL, cpu);
        else
                scx_exit(SCX_ECODE_ACT_RESTART | SCX_ECODE_RSN_HOTPLUG,
@@ -3621,6 +3638,8 @@ void scx_tick(struct rq *rq)
 
 static void task_tick_scx(struct rq *rq, struct task_struct *curr, int queued)
 {
+       struct scx_sched *sch = scx_root;
+
        update_curr_scx(rq);
 
        /*
@@ -3630,7 +3649,7 @@ static void task_tick_scx(struct rq *rq, struct task_struct *curr, int queued)
        if (scx_rq_bypassing(rq)) {
                curr->scx.slice = 0;
                touch_core_sched(rq, curr);
-       } else if (SCX_HAS_OP(scx_root, tick)) {
+       } else if (SCX_HAS_OP(sch, tick)) {
                SCX_CALL_OP_TASK(SCX_KF_REST, tick, rq, curr);
        }
 
@@ -3698,11 +3717,12 @@ static void scx_set_task_state(struct task_struct *p, enum scx_task_state state)
 
 static int scx_init_task(struct task_struct *p, struct task_group *tg, bool fork)
 {
+       struct scx_sched *sch = scx_root;
        int ret;
 
        p->scx.disallow = false;
 
-       if (SCX_HAS_OP(scx_root, init_task)) {
+       if (SCX_HAS_OP(sch, init_task)) {
                struct scx_init_task_args args = {
                        SCX_INIT_TASK_ARGS_CGROUP(tg)
                        .fork = fork,
@@ -3749,6 +3769,7 @@ static int scx_init_task(struct task_struct *p, struct task_group *tg, bool fork
 
 static void scx_enable_task(struct task_struct *p)
 {
+       struct scx_sched *sch = scx_root;
        struct rq *rq = task_rq(p);
        u32 weight;
 
@@ -3765,28 +3786,30 @@ static void scx_enable_task(struct task_struct *p)
 
        p->scx.weight = sched_weight_to_cgroup(weight);
 
-       if (SCX_HAS_OP(scx_root, enable))
+       if (SCX_HAS_OP(sch, enable))
                SCX_CALL_OP_TASK(SCX_KF_REST, enable, rq, p);
        scx_set_task_state(p, SCX_TASK_ENABLED);
 
-       if (SCX_HAS_OP(scx_root, set_weight))
+       if (SCX_HAS_OP(sch, set_weight))
                SCX_CALL_OP_TASK(SCX_KF_REST, set_weight, rq, p, p->scx.weight);
 }
 
 static void scx_disable_task(struct task_struct *p)
 {
+       struct scx_sched *sch = scx_root;
        struct rq *rq = task_rq(p);
 
        lockdep_assert_rq_held(rq);
        WARN_ON_ONCE(scx_get_task_state(p) != SCX_TASK_ENABLED);
 
-       if (SCX_HAS_OP(scx_root, disable))
+       if (SCX_HAS_OP(sch, disable))
                SCX_CALL_OP_TASK(SCX_KF_REST, disable, rq, p);
        scx_set_task_state(p, SCX_TASK_READY);
 }
 
 static void scx_exit_task(struct task_struct *p)
 {
+       struct scx_sched *sch = scx_root;
        struct scx_exit_task_args args = {
                .cancelled = false,
        };
@@ -3809,7 +3832,7 @@ static void scx_exit_task(struct task_struct *p)
                return;
        }
 
-       if (SCX_HAS_OP(scx_root, exit_task))
+       if (SCX_HAS_OP(sch, exit_task))
                SCX_CALL_OP_TASK(SCX_KF_REST, exit_task, task_rq(p), p, &args);
        scx_set_task_state(p, SCX_TASK_NONE);
 }
@@ -3915,10 +3938,12 @@ void sched_ext_free(struct task_struct *p)
 static void reweight_task_scx(struct rq *rq, struct task_struct *p,
                              const struct load_weight *lw)
 {
+       struct scx_sched *sch = scx_root;
+
        lockdep_assert_rq_held(task_rq(p));
 
        p->scx.weight = sched_weight_to_cgroup(scale_load_down(lw->weight));
-       if (SCX_HAS_OP(scx_root, set_weight))
+       if (SCX_HAS_OP(sch, set_weight))
                SCX_CALL_OP_TASK(SCX_KF_REST, set_weight, rq, p, p->scx.weight);
 }
 
@@ -3928,13 +3953,15 @@ static void prio_changed_scx(struct rq *rq, struct task_struct *p, int oldprio)
 
 static void switching_to_scx(struct rq *rq, struct task_struct *p)
 {
+       struct scx_sched *sch = scx_root;
+
        scx_enable_task(p);
 
        /*
         * set_cpus_allowed_scx() is not called while @p is associated with a
         * different scheduler class. Keep the BPF scheduler up-to-date.
         */
-       if (SCX_HAS_OP(scx_root, set_cpumask))
+       if (SCX_HAS_OP(sch, set_cpumask))
                SCX_CALL_OP_TASK(SCX_KF_REST, set_cpumask, rq,
                                 p, (struct cpumask *)p->cpus_ptr);
 }
@@ -3986,6 +4013,7 @@ static bool scx_cgroup_enabled;
 
 int scx_tg_online(struct task_group *tg)
 {
+       struct scx_sched *sch = scx_root;
        int ret = 0;
 
        WARN_ON_ONCE(tg->scx_flags & (SCX_TG_ONLINE | SCX_TG_INITED));
@@ -3993,7 +4021,7 @@ int scx_tg_online(struct task_group *tg)
        percpu_down_read(&scx_cgroup_rwsem);
 
        if (scx_cgroup_enabled) {
-               if (SCX_HAS_OP(scx_root, cgroup_init)) {
+               if (SCX_HAS_OP(sch, cgroup_init)) {
                        struct scx_cgroup_init_args args =
                                { .weight = tg->scx_weight };
 
@@ -4014,11 +4042,13 @@ int scx_tg_online(struct task_group *tg)
 
 void scx_tg_offline(struct task_group *tg)
 {
+       struct scx_sched *sch = scx_root;
+
        WARN_ON_ONCE(!(tg->scx_flags & SCX_TG_ONLINE));
 
        percpu_down_read(&scx_cgroup_rwsem);
 
-       if (scx_cgroup_enabled && SCX_HAS_OP(scx_root, cgroup_exit) &&
+       if (scx_cgroup_enabled && SCX_HAS_OP(sch, cgroup_exit) &&
            (tg->scx_flags & SCX_TG_INITED))
                SCX_CALL_OP(SCX_KF_UNLOCKED, cgroup_exit, NULL, tg->css.cgroup);
        tg->scx_flags &= ~(SCX_TG_ONLINE | SCX_TG_INITED);
@@ -4028,6 +4058,7 @@ void scx_tg_offline(struct task_group *tg)
 
 int scx_cgroup_can_attach(struct cgroup_taskset *tset)
 {
+       struct scx_sched *sch = scx_root;
        struct cgroup_subsys_state *css;
        struct task_struct *p;
        int ret;
@@ -4052,7 +4083,7 @@ int scx_cgroup_can_attach(struct cgroup_taskset *tset)
                if (from == to)
                        continue;
 
-               if (SCX_HAS_OP(scx_root, cgroup_prep_move)) {
+               if (SCX_HAS_OP(sch, cgroup_prep_move)) {
                        ret = SCX_CALL_OP_RET(SCX_KF_UNLOCKED, cgroup_prep_move, NULL,
                                              p, from, css->cgroup);
                        if (ret)
@@ -4066,7 +4097,7 @@ int scx_cgroup_can_attach(struct cgroup_taskset *tset)
 
 err:
        cgroup_taskset_for_each(p, css, tset) {
-               if (SCX_HAS_OP(scx_root, cgroup_cancel_move) &&
+               if (SCX_HAS_OP(sch, cgroup_cancel_move) &&
                    p->scx.cgrp_moving_from)
                        SCX_CALL_OP(SCX_KF_UNLOCKED, cgroup_cancel_move, NULL,
                                    p, p->scx.cgrp_moving_from, css->cgroup);
@@ -4079,6 +4110,8 @@ err:
 
 void scx_cgroup_move_task(struct task_struct *p)
 {
+       struct scx_sched *sch = scx_root;
+
        if (!scx_cgroup_enabled)
                return;
 
@@ -4086,7 +4119,7 @@ void scx_cgroup_move_task(struct task_struct *p)
         * @p must have ops.cgroup_prep_move() called on it and thus
         * cgrp_moving_from set.
         */
-       if (SCX_HAS_OP(scx_root, cgroup_move) &&
+       if (SCX_HAS_OP(sch, cgroup_move) &&
            !WARN_ON_ONCE(!p->scx.cgrp_moving_from))
                SCX_CALL_OP_TASK(SCX_KF_UNLOCKED, cgroup_move, NULL,
                                 p, p->scx.cgrp_moving_from, tg_cgrp(task_group(p)));
@@ -4100,6 +4133,7 @@ void scx_cgroup_finish_attach(void)
 
 void scx_cgroup_cancel_attach(struct cgroup_taskset *tset)
 {
+       struct scx_sched *sch = scx_root;
        struct cgroup_subsys_state *css;
        struct task_struct *p;
 
@@ -4107,7 +4141,7 @@ void scx_cgroup_cancel_attach(struct cgroup_taskset *tset)
                goto out_unlock;
 
        cgroup_taskset_for_each(p, css, tset) {
-               if (SCX_HAS_OP(scx_root, cgroup_cancel_move) &&
+               if (SCX_HAS_OP(sch, cgroup_cancel_move) &&
                    p->scx.cgrp_moving_from)
                        SCX_CALL_OP(SCX_KF_UNLOCKED, cgroup_cancel_move, NULL,
                                    p, p->scx.cgrp_moving_from, css->cgroup);
@@ -4119,10 +4153,12 @@ out_unlock:
 
 void scx_group_set_weight(struct task_group *tg, unsigned long weight)
 {
+       struct scx_sched *sch = scx_root;
+
        percpu_down_read(&scx_cgroup_rwsem);
 
        if (scx_cgroup_enabled && tg->scx_weight != weight) {
-               if (SCX_HAS_OP(scx_root, cgroup_set_weight))
+               if (SCX_HAS_OP(sch, cgroup_set_weight))
                        SCX_CALL_OP(SCX_KF_UNLOCKED, cgroup_set_weight, NULL,
                                    tg_cgrp(tg), weight);
                tg->scx_weight = weight;
@@ -4263,7 +4299,7 @@ out_unlock_rcu:
 }
 
 #ifdef CONFIG_EXT_GROUP_SCHED
-static void scx_cgroup_exit(void)
+static void scx_cgroup_exit(struct scx_sched *sch)
 {
        struct cgroup_subsys_state *css;
 
@@ -4283,7 +4319,7 @@ static void scx_cgroup_exit(void)
                        continue;
                tg->scx_flags &= ~SCX_TG_INITED;
 
-               if (!scx_root->ops.cgroup_exit)
+               if (!sch->ops.cgroup_exit)
                        continue;
 
                if (WARN_ON_ONCE(!css_tryget(css)))
@@ -4298,7 +4334,7 @@ static void scx_cgroup_exit(void)
        rcu_read_unlock();
 }
 
-static int scx_cgroup_init(void)
+static int scx_cgroup_init(struct scx_sched *sch)
 {
        struct cgroup_subsys_state *css;
        int ret;
@@ -4318,7 +4354,7 @@ static int scx_cgroup_init(void)
                     (SCX_TG_ONLINE | SCX_TG_INITED)) != SCX_TG_ONLINE)
                        continue;
 
-               if (!scx_root->ops.cgroup_init) {
+               if (!sch->ops.cgroup_init) {
                        tg->scx_flags |= SCX_TG_INITED;
                        continue;
                }
@@ -4348,8 +4384,8 @@ static int scx_cgroup_init(void)
 }
 
 #else
-static void scx_cgroup_exit(void) {}
-static int scx_cgroup_init(void) { return 0; }
+static void scx_cgroup_exit(struct scx_sched *sch) {}
+static int scx_cgroup_init(struct scx_sched *sch) { return 0; }
 #endif
 
 
@@ -4792,7 +4828,7 @@ static void scx_disable_workfn(struct kthread_work *work)
         * doesn't race against scx_exit_task().
         */
        scx_cgroup_lock();
-       scx_cgroup_exit();
+       scx_cgroup_exit(sch);
        scx_cgroup_unlock();
 
        /*
@@ -5018,6 +5054,7 @@ static void scx_dump_task(struct seq_buf *s, struct scx_dump_ctx *dctx,
                          struct task_struct *p, char marker)
 {
        static unsigned long bt[SCX_EXIT_BT_LEN];
+       struct scx_sched *sch = scx_root;
        char dsq_id_buf[19] = "(n/a)";
        unsigned long ops_state = atomic_long_read(&p->scx.ops_state);
        unsigned int bt_len = 0;
@@ -5040,7 +5077,7 @@ static void scx_dump_task(struct seq_buf *s, struct scx_dump_ctx *dctx,
                  p->scx.dsq_vtime, p->scx.slice, p->scx.weight);
        dump_line(s, "      cpus=%*pb", cpumask_pr_args(p->cpus_ptr));
 
-       if (SCX_HAS_OP(scx_root, dump_task)) {
+       if (SCX_HAS_OP(sch, dump_task)) {
                ops_dump_init(s, "    ");
                SCX_CALL_OP(SCX_KF_REST, dump_task, NULL, dctx, p);
                ops_dump_exit();
@@ -5059,6 +5096,7 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
 {
        static DEFINE_SPINLOCK(dump_lock);
        static const char trunc_marker[] = "\n\n~~~~ TRUNCATED ~~~~\n";
+       struct scx_sched *sch = scx_root;
        struct scx_dump_ctx dctx = {
                .kind = ei->kind,
                .exit_code = ei->exit_code,
@@ -5087,7 +5125,7 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
                dump_stack_trace(&s, "  ", ei->bt, ei->bt_len);
        }
 
-       if (SCX_HAS_OP(scx_root, dump)) {
+       if (SCX_HAS_OP(sch, dump)) {
                ops_dump_init(&s, "");
                SCX_CALL_OP(SCX_KF_UNLOCKED, dump, NULL, &dctx);
                ops_dump_exit();
@@ -5110,7 +5148,7 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
                idle = list_empty(&rq->scx.runnable_list) &&
                        rq->curr->sched_class == &idle_sched_class;
 
-               if (idle && !SCX_HAS_OP(scx_root, dump_cpu))
+               if (idle && !SCX_HAS_OP(sch, dump_cpu))
                        goto next;
 
                /*
@@ -5144,7 +5182,7 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
                                  cpumask_pr_args(rq->scx.cpus_to_wait));
 
                used = seq_buf_used(&ns);
-               if (SCX_HAS_OP(scx_root, dump_cpu)) {
+               if (SCX_HAS_OP(sch, dump_cpu)) {
                        ops_dump_init(&ns, "  ");
                        SCX_CALL_OP(SCX_KF_REST, dump_cpu, NULL, &dctx, cpu, idle);
                        ops_dump_exit();
@@ -5180,7 +5218,7 @@ static void scx_dump_state(struct scx_exit_info *ei, size_t dump_len)
        dump_line(&s, "Event counters");
        dump_line(&s, "--------------");
 
-       scx_read_events(scx_root, &events);
+       scx_read_events(sch, &events);
        scx_dump_event(s, &events, SCX_EV_SELECT_CPU_FALLBACK);
        scx_dump_event(s, &events, SCX_EV_DISPATCH_LOCAL_DSQ_OFFLINE);
        scx_dump_event(s, &events, SCX_EV_DISPATCH_KEEP_LAST);
@@ -5505,7 +5543,7 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
         * never sees uninitialized tasks.
         */
        scx_cgroup_lock();
-       ret = scx_cgroup_init();
+       ret = scx_cgroup_init(sch);
        if (ret)
                goto err_disable_unlock_all;
 
@@ -6039,6 +6077,7 @@ static void kick_cpus_irq_workfn(struct irq_work *irq_work)
  */
 void print_scx_info(const char *log_lvl, struct task_struct *p)
 {
+       struct scx_sched *sch = scx_root;
        enum scx_enable_state state = scx_enable_state();
        const char *all = READ_ONCE(scx_switching_all) ? "+all" : "";
        char runnable_at_buf[22] = "?";
@@ -6054,7 +6093,7 @@ void print_scx_info(const char *log_lvl, struct task_struct *p)
         */
        if (copy_from_kernel_nofault(&class, &p->sched_class, sizeof(class)) ||
            class != &ext_sched_class) {
-               printk("%sSched_ext: %s (%s%s)", log_lvl, scx_root->ops.name,
+               printk("%sSched_ext: %s (%s%s)", log_lvl, sch->ops.name,
                       scx_enable_state_str[state], all);
                return;
        }
@@ -6066,7 +6105,7 @@ void print_scx_info(const char *log_lvl, struct task_struct *p)
 
        /* print everything onto one line to conserve console space */
        printk("%sSched_ext: %s (%s%s), task: runnable_at=%s",
-              log_lvl, scx_root->ops.name, scx_enable_state_str[state], all,
+              log_lvl, sch->ops.name, scx_enable_state_str[state], all,
               runnable_at_buf);
 }
 
@@ -6844,7 +6883,7 @@ __bpf_kfunc s32 scx_bpf_dsq_nr_queued(u64 dsq_id)
        preempt_disable();
 
        sch = rcu_dereference_sched(scx_root);
-       if (!sch) {
+       if (unlikely(!sch)) {
                ret = -ENODEV;
                goto out;
        }
@@ -6920,7 +6959,7 @@ __bpf_kfunc int bpf_iter_scx_dsq_new(struct bpf_iter_scx_dsq *it, u64 dsq_id,
        kit->dsq = NULL;
 
        sch = rcu_dereference_check(scx_root, rcu_read_lock_bh_held());
-       if (!sch)
+       if (unlikely(!sch))
                return -ENODEV;
 
        if (flags & ~__SCX_DSQ_ITER_USER_FLAGS)

diff --git a/kernel/sched/ext_idle.c b/kernel/sched/ext_idle.c
index 6915685cd3d6b9cc8a3df53a8af23f845883c996..0a116bcd681bbc576b4fea41be23c07abf42f8aa 100644 (file)
--- a/kernel/sched/ext_idle.c
+++ b/kernel/sched/ext_idle.c
@@ -733,6 +733,7 @@ static void update_builtin_idle(int cpu, bool idle)
  */
 void __scx_update_idle(struct rq *rq, bool idle, bool do_notify)
 {
+       struct scx_sched *sch = scx_root;
        int cpu = cpu_of(rq);
 
        lockdep_assert_rq_held(rq);
@@ -744,8 +745,7 @@ void __scx_update_idle(struct rq *rq, bool idle, bool do_notify)
         * Idle transitions are indicated by do_notify being set to true,
         * managed by put_prev_task_idle()/set_next_task_idle().
         */
-       if (SCX_HAS_OP(scx_root, update_idle) &&
-           do_notify && !scx_rq_bypassing(rq))
+       if (SCX_HAS_OP(sch, update_idle) && do_notify && !scx_rq_bypassing(rq))
                SCX_CALL_OP(SCX_KF_REST, update_idle, rq, cpu_of(rq), idle);
 
        /*