Re: [PATCH 05/15] sched_ext: Relocate reenq_local() and run_deferred()

["Emil Tsalapatis" <emil@etsalapatis.com>]

On Fri Mar 6, 2026 at 2:06 PM EST, Tejun Heo wrote:
> Previously, both process_ddsp_deferred_locals() and reenq_local() required
> forward declarations. Reorganize so that only run_deferred() needs to be
> declared. This reduces forward declaration clutter and will ease adding more
> to the run_deferred() path.
>
> No functional changes.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>

Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>

> ---
>  kernel/sched/ext.c | 132 ++++++++++++++++++++++-----------------------
>  1 file changed, 65 insertions(+), 67 deletions(-)
>
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index c44893878878..1b6cd1e4f8b9 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -193,9 +193,8 @@ MODULE_PARM_DESC(bypass_lb_intv_us, "bypass load balance interval in microsecond
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/sched_ext.h>
>  
> -static void process_ddsp_deferred_locals(struct rq *rq);
> +static void run_deferred(struct rq *rq);
>  static bool task_dead_and_done(struct task_struct *p);
> -static u32 reenq_local(struct scx_sched *sch, struct rq *rq);
>  static void scx_kick_cpu(struct scx_sched *sch, s32 cpu, u64 flags);
>  static void scx_disable(struct scx_sched *sch, enum scx_exit_kind kind);
>  static bool scx_vexit(struct scx_sched *sch, enum scx_exit_kind kind,
> @@ -1003,23 +1002,6 @@ static int ops_sanitize_err(struct scx_sched *sch, const char *ops_name, s32 err
>  	return -EPROTO;
>  }
>  
> -static void run_deferred(struct rq *rq)
> -{
> -	process_ddsp_deferred_locals(rq);
> -
> -	if (!llist_empty(&rq->scx.deferred_reenq_locals)) {
> -		struct llist_node *llist =
> -			llist_del_all(&rq->scx.deferred_reenq_locals);
> -		struct scx_sched_pcpu *pos, *next;
> -
> -		llist_for_each_entry_safe(pos, next, llist,
> -					  deferred_reenq_locals_node) {
> -			init_llist_node(&pos->deferred_reenq_locals_node);
> -			reenq_local(pos->sch, rq);
> -		}
> -	}
> -}
> -
>  static void deferred_bal_cb_workfn(struct rq *rq)
>  {
>  	run_deferred(rq);
> @@ -3072,7 +3054,6 @@ static void rq_offline_scx(struct rq *rq)
>  	rq->scx.flags &= ~SCX_RQ_ONLINE;
>  }
>  
> -
>  static bool check_rq_for_timeouts(struct rq *rq)
>  {
>  	struct scx_sched *sch;
> @@ -3612,6 +3593,70 @@ int scx_check_setscheduler(struct task_struct *p, int policy)
>  	return 0;
>  }
>  
> +static u32 reenq_local(struct scx_sched *sch, struct rq *rq)
> +{
> +	LIST_HEAD(tasks);
> +	u32 nr_enqueued = 0;
> +	struct task_struct *p, *n;
> +
> +	lockdep_assert_rq_held(rq);
> +
> +	/*
> +	 * The BPF scheduler may choose to dispatch tasks back to
> +	 * @rq->scx.local_dsq. Move all candidate tasks off to a private list
> +	 * first to avoid processing the same tasks repeatedly.
> +	 */
> +	list_for_each_entry_safe(p, n, &rq->scx.local_dsq.list,
> +				 scx.dsq_list.node) {
> +		struct scx_sched *task_sch = scx_task_sched(p);
> +
> +		/*
> +		 * If @p is being migrated, @p's current CPU may not agree with
> +		 * its allowed CPUs and the migration_cpu_stop is about to
> +		 * deactivate and re-activate @p anyway. Skip re-enqueueing.
> +		 *
> +		 * While racing sched property changes may also dequeue and
> +		 * re-enqueue a migrating task while its current CPU and allowed
> +		 * CPUs disagree, they use %ENQUEUE_RESTORE which is bypassed to
> +		 * the current local DSQ for running tasks and thus are not
> +		 * visible to the BPF scheduler.
> +		 */
> +		if (p->migration_pending)
> +			continue;
> +
> +		if (!scx_is_descendant(task_sch, sch))
> +			continue;
> +
> +		dispatch_dequeue(rq, p);
> +		list_add_tail(&p->scx.dsq_list.node, &tasks);
> +	}
> +
> +	list_for_each_entry_safe(p, n, &tasks, scx.dsq_list.node) {
> +		list_del_init(&p->scx.dsq_list.node);
> +		do_enqueue_task(rq, p, SCX_ENQ_REENQ, -1);
> +		nr_enqueued++;
> +	}
> +
> +	return nr_enqueued;
> +}
> +
> +static void run_deferred(struct rq *rq)
> +{
> +	process_ddsp_deferred_locals(rq);
> +
> +	if (!llist_empty(&rq->scx.deferred_reenq_locals)) {
> +		struct llist_node *llist =
> +			llist_del_all(&rq->scx.deferred_reenq_locals);
> +		struct scx_sched_pcpu *pos, *next;
> +
> +		llist_for_each_entry_safe(pos, next, llist,
> +					  deferred_reenq_locals_node) {
> +			init_llist_node(&pos->deferred_reenq_locals_node);
> +			reenq_local(pos->sch, rq);
> +		}
> +	}
> +}
> +
>  #ifdef CONFIG_NO_HZ_FULL
>  bool scx_can_stop_tick(struct rq *rq)
>  {
> @@ -7702,53 +7747,6 @@ static const struct btf_kfunc_id_set scx_kfunc_set_dispatch = {
>  	.set			= &scx_kfunc_ids_dispatch,
>  };
>  
> -static u32 reenq_local(struct scx_sched *sch, struct rq *rq)
> -{
> -	LIST_HEAD(tasks);
> -	u32 nr_enqueued = 0;
> -	struct task_struct *p, *n;
> -
> -	lockdep_assert_rq_held(rq);
> -
> -	/*
> -	 * The BPF scheduler may choose to dispatch tasks back to
> -	 * @rq->scx.local_dsq. Move all candidate tasks off to a private list
> -	 * first to avoid processing the same tasks repeatedly.
> -	 */
> -	list_for_each_entry_safe(p, n, &rq->scx.local_dsq.list,
> -				 scx.dsq_list.node) {
> -		struct scx_sched *task_sch = scx_task_sched(p);
> -
> -		/*
> -		 * If @p is being migrated, @p's current CPU may not agree with
> -		 * its allowed CPUs and the migration_cpu_stop is about to
> -		 * deactivate and re-activate @p anyway. Skip re-enqueueing.
> -		 *
> -		 * While racing sched property changes may also dequeue and
> -		 * re-enqueue a migrating task while its current CPU and allowed
> -		 * CPUs disagree, they use %ENQUEUE_RESTORE which is bypassed to
> -		 * the current local DSQ for running tasks and thus are not
> -		 * visible to the BPF scheduler.
> -		 */
> -		if (p->migration_pending)
> -			continue;
> -
> -		if (!scx_is_descendant(task_sch, sch))
> -			continue;
> -
> -		dispatch_dequeue(rq, p);
> -		list_add_tail(&p->scx.dsq_list.node, &tasks);
> -	}
> -
> -	list_for_each_entry_safe(p, n, &tasks, scx.dsq_list.node) {
> -		list_del_init(&p->scx.dsq_list.node);
> -		do_enqueue_task(rq, p, SCX_ENQ_REENQ, -1);
> -		nr_enqueued++;
> -	}
> -
> -	return nr_enqueued;
> -}
> -
>  __bpf_kfunc_start_defs();
>  
>  /**