[PATCH 0/2] sched_ext: Update demo schedulers and selftests for deprecated APIs

[PATCH 0/2] sched_ext: Update demo schedulers and selftests for deprecated APIs

[Cheng-Yang Chou]

Two sets of sched_ext APIs have been deprecated:

- Direct writes to p->scx.dsq_vtime in favor of 
  scx_bpf_task_set_dsq_vtime()
- ops.cpu_acquire/release() in favor of handling CPU preemption via the
  sched_switch tracepoint

This series updates the demo schedulers (scx_simple, scx_flatcg,
scx_qmap) and selftests (select_cpu_vtime, maximal) to use the new
APIs, keeping them in sync with current best practices.

Patch 1 uses bpf_ksym_exists() to fall back to direct assignment on
older kernels that don't have scx_bpf_task_set_dsq_vtime(), preserving
backwards compatibility.

Patch 2 removes the cpu_acquire/release stubs and the
__COMPAT_scx_bpf_reenqueue_local_from_anywhere() compat guard from
scx_qmap, unconditionally relying on the sched_switch TP.

Thanks,
Cheng-Yang

---

Cheng-Yang Chou (2):
  sched_ext: Update demo schedulers and selftests to use
    scx_bpf_task_set_dsq_vtime()
  sched_ext: Update demo schedulers and selftests to drop
    ops.cpu_acquire/release()

 tools/sched_ext/scx_flatcg.bpf.c              | 21 ++++++++++++++-----
 tools/sched_ext/scx_qmap.bpf.c                | 15 ++-----------
 tools/sched_ext/scx_simple.bpf.c              | 12 +++++++++--
 .../testing/selftests/sched_ext/maximal.bpf.c | 15 ++++++-------
 .../sched_ext/select_cpu_vtime.bpf.c          | 13 ++++++++++--
 5 files changed, 45 insertions(+), 31 deletions(-)

-- 
2.48.1

[PATCH 1/2] sched_ext: Update demo schedulers and selftests to use scx_bpf_task_set_dsq_vtime()

[Cheng-Yang Chou]

Direct writes to p->scx.dsq_vtime are deprecated in favor of
scx_bpf_task_set_dsq_vtime(). Update scx_simple, scx_flatcg, and
select_cpu_vtime selftest to use the new kfunc.

Use bpf_ksym_exists() to fall back to direct assignment on older kernels
that don't have the new kfunc, preserving backwards compatibility.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
---
 tools/sched_ext/scx_flatcg.bpf.c              | 21 ++++++++++++++-----
 tools/sched_ext/scx_simple.bpf.c              | 12 +++++++++--
 .../sched_ext/select_cpu_vtime.bpf.c          | 13 ++++++++++--
 3 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/tools/sched_ext/scx_flatcg.bpf.c b/tools/sched_ext/scx_flatcg.bpf.c
index a8a9234bb41e..27d99bb1e60f 100644
--- a/tools/sched_ext/scx_flatcg.bpf.c
+++ b/tools/sched_ext/scx_flatcg.bpf.c
@@ -551,9 +551,14 @@ void BPF_STRUCT_OPS(fcg_stopping, struct task_struct *p, bool runnable)
 	 * too much, determine the execution time by taking explicit timestamps
 	 * instead of depending on @p->scx.slice.
 	 */
-	if (!fifo_sched)
-		p->scx.dsq_vtime +=
-			(SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
+	u64 delta = (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
+
+	if (!fifo_sched) {
+		if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
+			scx_bpf_task_set_dsq_vtime___new(p, p->scx.dsq_vtime + delta);
+		else
+			p->scx.dsq_vtime += delta;
+	}
 
 	taskc = bpf_task_storage_get(&task_ctx, p, 0, 0);
 	if (!taskc) {
@@ -822,7 +827,10 @@ s32 BPF_STRUCT_OPS(fcg_init_task, struct task_struct *p,
 	if (!(cgc = find_cgrp_ctx(args->cgroup)))
 		return -ENOENT;
 
-	p->scx.dsq_vtime = cgc->tvtime_now;
+	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
+		scx_bpf_task_set_dsq_vtime___new(p, cgc->tvtime_now);
+	else
+		p->scx.dsq_vtime = cgc->tvtime_now;
 
 	return 0;
 }
@@ -924,7 +932,10 @@ void BPF_STRUCT_OPS(fcg_cgroup_move, struct task_struct *p,
 		return;
 
 	delta = time_delta(p->scx.dsq_vtime, from_cgc->tvtime_now);
-	p->scx.dsq_vtime = to_cgc->tvtime_now + delta;
+	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
+		scx_bpf_task_set_dsq_vtime___new(p, to_cgc->tvtime_now + delta);
+	else
+		p->scx.dsq_vtime = to_cgc->tvtime_now + delta;
 }
 
 s32 BPF_STRUCT_OPS_SLEEPABLE(fcg_init)
diff --git a/tools/sched_ext/scx_simple.bpf.c b/tools/sched_ext/scx_simple.bpf.c
index b456bd7cae77..61d3bcf54ce7 100644
--- a/tools/sched_ext/scx_simple.bpf.c
+++ b/tools/sched_ext/scx_simple.bpf.c
@@ -121,12 +121,20 @@ void BPF_STRUCT_OPS(simple_stopping, struct task_struct *p, bool runnable)
 	 * too much, determine the execution time by taking explicit timestamps
 	 * instead of depending on @p->scx.slice.
 	 */
-	p->scx.dsq_vtime += (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
+	u64 delta = (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
+
+	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
+		scx_bpf_task_set_dsq_vtime___new(p, p->scx.dsq_vtime + delta);
+	else
+		p->scx.dsq_vtime += delta;
 }
 
 void BPF_STRUCT_OPS(simple_enable, struct task_struct *p)
 {
-	p->scx.dsq_vtime = vtime_now;
+	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
+		scx_bpf_task_set_dsq_vtime___new(p, vtime_now);
+	else
+		p->scx.dsq_vtime = vtime_now;
 }
 
 s32 BPF_STRUCT_OPS_SLEEPABLE(simple_init)
diff --git a/tools/testing/selftests/sched_ext/select_cpu_vtime.bpf.c b/tools/testing/selftests/sched_ext/select_cpu_vtime.bpf.c
index bfcb96cd4954..17ed515c3e25 100644
--- a/tools/testing/selftests/sched_ext/select_cpu_vtime.bpf.c
+++ b/tools/testing/selftests/sched_ext/select_cpu_vtime.bpf.c
@@ -66,12 +66,21 @@ void BPF_STRUCT_OPS(select_cpu_vtime_running, struct task_struct *p)
 void BPF_STRUCT_OPS(select_cpu_vtime_stopping, struct task_struct *p,
 		    bool runnable)
 {
-	p->scx.dsq_vtime += (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
+	u64 delta = (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
+
+	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
+		scx_bpf_task_set_dsq_vtime___new(p, p->scx.dsq_vtime + delta);
+	else
+		p->scx.dsq_vtime += delta;
+
 }
 
 void BPF_STRUCT_OPS(select_cpu_vtime_enable, struct task_struct *p)
 {
-	p->scx.dsq_vtime = vtime_now;
+	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
+		scx_bpf_task_set_dsq_vtime___new(p, vtime_now);
+	else
+		p->scx.dsq_vtime = vtime_now;
 }
 
 s32 BPF_STRUCT_OPS_SLEEPABLE(select_cpu_vtime_init)
-- 
2.48.1

Re: [PATCH 1/2] sched_ext: Update demo schedulers and selftests to use scx_bpf_task_set_dsq_vtime()

[Andrea Righi]

Hi Cheng-Yang,

On Thu, Mar 12, 2026 at 12:20:00PM +0800, Cheng-Yang Chou wrote:
> Direct writes to p->scx.dsq_vtime are deprecated in favor of
> scx_bpf_task_set_dsq_vtime(). Update scx_simple, scx_flatcg, and
> select_cpu_vtime selftest to use the new kfunc.
> 
> Use bpf_ksym_exists() to fall back to direct assignment on older kernels
> that don't have the new kfunc, preserving backwards compatibility.
> 
> Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
> ---
>  tools/sched_ext/scx_flatcg.bpf.c              | 21 ++++++++++++++-----
>  tools/sched_ext/scx_simple.bpf.c              | 12 +++++++++--
>  .../sched_ext/select_cpu_vtime.bpf.c          | 13 ++++++++++--
>  3 files changed, 37 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/sched_ext/scx_flatcg.bpf.c b/tools/sched_ext/scx_flatcg.bpf.c
> index a8a9234bb41e..27d99bb1e60f 100644
> --- a/tools/sched_ext/scx_flatcg.bpf.c
> +++ b/tools/sched_ext/scx_flatcg.bpf.c
> @@ -551,9 +551,14 @@ void BPF_STRUCT_OPS(fcg_stopping, struct task_struct *p, bool runnable)
>  	 * too much, determine the execution time by taking explicit timestamps
>  	 * instead of depending on @p->scx.slice.
>  	 */
> -	if (!fifo_sched)
> -		p->scx.dsq_vtime +=
> -			(SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
> +	u64 delta = (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;

While at it, can we use:

 u64 delta = scale_by_task_weight(p, SCX_SLICE_DFL - p->scx.slice);

> +
> +	if (!fifo_sched) {
> +		if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
> +			scx_bpf_task_set_dsq_vtime___new(p, p->scx.dsq_vtime + delta);
> +		else
> +			p->scx.dsq_vtime += delta;
> +	}

No, let's just use:

 scx_bpf_task_set_dsq_vtime(p, p->scx.dsq_vtime + delta);

It's already doing the bpf_ksym_exists() logic internally, see
tools/sched_ext/include/scx/compat.bpf.h.

>  
>  	taskc = bpf_task_storage_get(&task_ctx, p, 0, 0);
>  	if (!taskc) {
> @@ -822,7 +827,10 @@ s32 BPF_STRUCT_OPS(fcg_init_task, struct task_struct *p,
>  	if (!(cgc = find_cgrp_ctx(args->cgroup)))
>  		return -ENOENT;
>  
> -	p->scx.dsq_vtime = cgc->tvtime_now;
> +	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
> +		scx_bpf_task_set_dsq_vtime___new(p, cgc->tvtime_now);
> +	else
> +		p->scx.dsq_vtime = cgc->tvtime_now;

Ditto.

>  
>  	return 0;
>  }
> @@ -924,7 +932,10 @@ void BPF_STRUCT_OPS(fcg_cgroup_move, struct task_struct *p,
>  		return;
>  
>  	delta = time_delta(p->scx.dsq_vtime, from_cgc->tvtime_now);
> -	p->scx.dsq_vtime = to_cgc->tvtime_now + delta;
> +	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
> +		scx_bpf_task_set_dsq_vtime___new(p, to_cgc->tvtime_now + delta);
> +	else
> +		p->scx.dsq_vtime = to_cgc->tvtime_now + delta;

Ditto.

>  }
>  
>  s32 BPF_STRUCT_OPS_SLEEPABLE(fcg_init)
> diff --git a/tools/sched_ext/scx_simple.bpf.c b/tools/sched_ext/scx_simple.bpf.c
> index b456bd7cae77..61d3bcf54ce7 100644
> --- a/tools/sched_ext/scx_simple.bpf.c
> +++ b/tools/sched_ext/scx_simple.bpf.c
> @@ -121,12 +121,20 @@ void BPF_STRUCT_OPS(simple_stopping, struct task_struct *p, bool runnable)
>  	 * too much, determine the execution time by taking explicit timestamps
>  	 * instead of depending on @p->scx.slice.
>  	 */
> -	p->scx.dsq_vtime += (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
> +	u64 delta = (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
> +
> +	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
> +		scx_bpf_task_set_dsq_vtime___new(p, p->scx.dsq_vtime + delta);
> +	else
> +		p->scx.dsq_vtime += delta;

Ditto.

>  }
>  
>  void BPF_STRUCT_OPS(simple_enable, struct task_struct *p)
>  {
> -	p->scx.dsq_vtime = vtime_now;
> +	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
> +		scx_bpf_task_set_dsq_vtime___new(p, vtime_now);
> +	else
> +		p->scx.dsq_vtime = vtime_now;

Ditto.

>  }
>  
>  s32 BPF_STRUCT_OPS_SLEEPABLE(simple_init)
> diff --git a/tools/testing/selftests/sched_ext/select_cpu_vtime.bpf.c b/tools/testing/selftests/sched_ext/select_cpu_vtime.bpf.c
> index bfcb96cd4954..17ed515c3e25 100644
> --- a/tools/testing/selftests/sched_ext/select_cpu_vtime.bpf.c
> +++ b/tools/testing/selftests/sched_ext/select_cpu_vtime.bpf.c
> @@ -66,12 +66,21 @@ void BPF_STRUCT_OPS(select_cpu_vtime_running, struct task_struct *p)
>  void BPF_STRUCT_OPS(select_cpu_vtime_stopping, struct task_struct *p,
>  		    bool runnable)
>  {
> -	p->scx.dsq_vtime += (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;
> +	u64 delta = (SCX_SLICE_DFL - p->scx.slice) * 100 / p->scx.weight;

Ditto (scale_by_task_weight).

> +
> +	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
> +		scx_bpf_task_set_dsq_vtime___new(p, p->scx.dsq_vtime + delta);
> +	else
> +		p->scx.dsq_vtime += delta;
> +

Ditto.

>  }
>  
>  void BPF_STRUCT_OPS(select_cpu_vtime_enable, struct task_struct *p)
>  {
> -	p->scx.dsq_vtime = vtime_now;
> +	if (bpf_ksym_exists(scx_bpf_task_set_dsq_vtime___new))
> +		scx_bpf_task_set_dsq_vtime___new(p, vtime_now);
> +	else
> +		p->scx.dsq_vtime = vtime_now;

Ditto.

>  }
>  
>  s32 BPF_STRUCT_OPS_SLEEPABLE(select_cpu_vtime_init)
> -- 
> 2.48.1
> 

Thanks,
-Andrea

[PATCH 2/2] sched_ext: Update demo schedulers and selftests to drop ops.cpu_acquire/release()

[Cheng-Yang Chou]

ops.cpu_acquire() and ops.cpu_release() are deprecated in favor of
handling CPU preemption via the sched_switch tracepoint. Update scx_qmap
and the maximal selftest to use the new approach.

In scx_qmap, remove the cpu_release fallback and the
__COMPAT_scx_bpf_reenqueue_local_from_anywhere() compat guard from
qmap_sched_switch(), unconditionally handling preemption via the TP.

In the maximal selftest, replace the cpu_acquire and cpu_release stubs
with a minimal sched_switch TP program.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
---
 tools/sched_ext/scx_qmap.bpf.c                  | 15 ++-------------
 tools/testing/selftests/sched_ext/maximal.bpf.c | 15 ++++++---------
 2 files changed, 8 insertions(+), 22 deletions(-)

diff --git a/tools/sched_ext/scx_qmap.bpf.c b/tools/sched_ext/scx_qmap.bpf.c
index a4a1b84fe359..a11e27c8de77 100644
--- a/tools/sched_ext/scx_qmap.bpf.c
+++ b/tools/sched_ext/scx_qmap.bpf.c
@@ -11,8 +11,8 @@
  *
  * - BPF-side queueing using PIDs.
  * - Sleepable per-task storage allocation using ops.prep_enable().
- * - Using ops.cpu_release() to handle a higher priority scheduling class taking
- *   the CPU away.
+ * - Using the sched_switch tracepoint to handle a higher priority scheduling
+ *   class taking the CPU away.
  * - Core-sched support.
  *
  * This scheduler is primarily for demonstration and testing of sched_ext
@@ -562,9 +562,6 @@ SEC("tp_btf/sched_switch")
 int BPF_PROG(qmap_sched_switch, bool preempt, struct task_struct *prev,
 	     struct task_struct *next, unsigned long prev_state)
 {
-	if (!__COMPAT_scx_bpf_reenqueue_local_from_anywhere())
-		return 0;
-
 	/*
 	 * If @cpu is taken by a higher priority scheduling class, it is no
 	 * longer available for executing sched_ext tasks. As we don't want the
@@ -586,13 +583,6 @@ int BPF_PROG(qmap_sched_switch, bool preempt, struct task_struct *prev,
 	return 0;
 }
 
-void BPF_STRUCT_OPS(qmap_cpu_release, s32 cpu, struct scx_cpu_release_args *args)
-{
-	/* see qmap_sched_switch() to learn how to do this on newer kernels */
-	if (!__COMPAT_scx_bpf_reenqueue_local_from_anywhere())
-		scx_bpf_reenqueue_local();
-}
-
 s32 BPF_STRUCT_OPS(qmap_init_task, struct task_struct *p,
 		   struct scx_init_task_args *args)
 {
@@ -999,7 +989,6 @@ SCX_OPS_DEFINE(qmap_ops,
 	       .dispatch		= (void *)qmap_dispatch,
 	       .tick			= (void *)qmap_tick,
 	       .core_sched_before	= (void *)qmap_core_sched_before,
-	       .cpu_release		= (void *)qmap_cpu_release,
 	       .init_task		= (void *)qmap_init_task,
 	       .dump			= (void *)qmap_dump,
 	       .dump_cpu		= (void *)qmap_dump_cpu,
diff --git a/tools/testing/selftests/sched_ext/maximal.bpf.c b/tools/testing/selftests/sched_ext/maximal.bpf.c
index 01cf4f3da4e0..5858f64313e9 100644
--- a/tools/testing/selftests/sched_ext/maximal.bpf.c
+++ b/tools/testing/selftests/sched_ext/maximal.bpf.c
@@ -67,13 +67,12 @@ void BPF_STRUCT_OPS(maximal_set_cpumask, struct task_struct *p,
 void BPF_STRUCT_OPS(maximal_update_idle, s32 cpu, bool idle)
 {}
 
-void BPF_STRUCT_OPS(maximal_cpu_acquire, s32 cpu,
-		    struct scx_cpu_acquire_args *args)
-{}
-
-void BPF_STRUCT_OPS(maximal_cpu_release, s32 cpu,
-		    struct scx_cpu_release_args *args)
-{}
+SEC("tp_btf/sched_switch")
+int BPF_PROG(maximal_sched_switch, bool preempt, struct task_struct *prev,
+	     struct task_struct *next, unsigned long prev_state)
+{
+	return 0;
+}
 
 void BPF_STRUCT_OPS(maximal_cpu_online, s32 cpu)
 {}
@@ -150,8 +149,6 @@ struct sched_ext_ops maximal_ops = {
 	.set_weight		= (void *) maximal_set_weight,
 	.set_cpumask		= (void *) maximal_set_cpumask,
 	.update_idle		= (void *) maximal_update_idle,
-	.cpu_acquire		= (void *) maximal_cpu_acquire,
-	.cpu_release		= (void *) maximal_cpu_release,
 	.cpu_online		= (void *) maximal_cpu_online,
 	.cpu_offline		= (void *) maximal_cpu_offline,
 	.init_task		= (void *) maximal_init_task,
-- 
2.48.1

Re: [PATCH 2/2] sched_ext: Update demo schedulers and selftests to drop ops.cpu_acquire/release()

[Andrea Righi]

Hi Cheng-Yang,

On Thu, Mar 12, 2026 at 12:20:01PM +0800, Cheng-Yang Chou wrote:
> ops.cpu_acquire() and ops.cpu_release() are deprecated in favor of
> handling CPU preemption via the sched_switch tracepoint. Update scx_qmap
> and the maximal selftest to use the new approach.

We could mention that commit a3f5d4822253 ("sched_ext: Allow
scx_bpf_reenqueue_local() to be called from anywhere") is deprecating
ops.cpu_acquire/relese().

> 
> In scx_qmap, remove the cpu_release fallback and the
> __COMPAT_scx_bpf_reenqueue_local_from_anywhere() compat guard from
> qmap_sched_switch(), unconditionally handling preemption via the TP.
> 
> In the maximal selftest, replace the cpu_acquire and cpu_release stubs
> with a minimal sched_switch TP program.
> 
> Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
> ---
>  tools/sched_ext/scx_qmap.bpf.c                  | 15 ++-------------
>  tools/testing/selftests/sched_ext/maximal.bpf.c | 15 ++++++---------
>  2 files changed, 8 insertions(+), 22 deletions(-)
> 
> diff --git a/tools/sched_ext/scx_qmap.bpf.c b/tools/sched_ext/scx_qmap.bpf.c
> index a4a1b84fe359..a11e27c8de77 100644
> --- a/tools/sched_ext/scx_qmap.bpf.c
> +++ b/tools/sched_ext/scx_qmap.bpf.c
> @@ -11,8 +11,8 @@
>   *
>   * - BPF-side queueing using PIDs.
>   * - Sleepable per-task storage allocation using ops.prep_enable().
> - * - Using ops.cpu_release() to handle a higher priority scheduling class taking
> - *   the CPU away.
> + * - Using the sched_switch tracepoint to handle a higher priority scheduling
> + *   class taking the CPU away.
>   * - Core-sched support.
>   *
>   * This scheduler is primarily for demonstration and testing of sched_ext
> @@ -562,9 +562,6 @@ SEC("tp_btf/sched_switch")
>  int BPF_PROG(qmap_sched_switch, bool preempt, struct task_struct *prev,
>  	     struct task_struct *next, unsigned long prev_state)
>  {
> -	if (!__COMPAT_scx_bpf_reenqueue_local_from_anywhere())
> -		return 0;
> -
>  	/*
>  	 * If @cpu is taken by a higher priority scheduling class, it is no
>  	 * longer available for executing sched_ext tasks. As we don't want the
> @@ -586,13 +583,6 @@ int BPF_PROG(qmap_sched_switch, bool preempt, struct task_struct *prev,
>  	return 0;
>  }
>  
> -void BPF_STRUCT_OPS(qmap_cpu_release, s32 cpu, struct scx_cpu_release_args *args)
> -{
> -	/* see qmap_sched_switch() to learn how to do this on newer kernels */
> -	if (!__COMPAT_scx_bpf_reenqueue_local_from_anywhere())
> -		scx_bpf_reenqueue_local();
> -}
> -
>  s32 BPF_STRUCT_OPS(qmap_init_task, struct task_struct *p,
>  		   struct scx_init_task_args *args)
>  {
> @@ -999,7 +989,6 @@ SCX_OPS_DEFINE(qmap_ops,
>  	       .dispatch		= (void *)qmap_dispatch,
>  	       .tick			= (void *)qmap_tick,
>  	       .core_sched_before	= (void *)qmap_core_sched_before,
> -	       .cpu_release		= (void *)qmap_cpu_release,
>  	       .init_task		= (void *)qmap_init_task,
>  	       .dump			= (void *)qmap_dump,
>  	       .dump_cpu		= (void *)qmap_dump_cpu,
> diff --git a/tools/testing/selftests/sched_ext/maximal.bpf.c b/tools/testing/selftests/sched_ext/maximal.bpf.c
> index 01cf4f3da4e0..5858f64313e9 100644
> --- a/tools/testing/selftests/sched_ext/maximal.bpf.c
> +++ b/tools/testing/selftests/sched_ext/maximal.bpf.c
> @@ -67,13 +67,12 @@ void BPF_STRUCT_OPS(maximal_set_cpumask, struct task_struct *p,
>  void BPF_STRUCT_OPS(maximal_update_idle, s32 cpu, bool idle)
>  {}
>  
> -void BPF_STRUCT_OPS(maximal_cpu_acquire, s32 cpu,
> -		    struct scx_cpu_acquire_args *args)
> -{}
> -
> -void BPF_STRUCT_OPS(maximal_cpu_release, s32 cpu,
> -		    struct scx_cpu_release_args *args)
> -{}
> +SEC("tp_btf/sched_switch")
> +int BPF_PROG(maximal_sched_switch, bool preempt, struct task_struct *prev,
> +	     struct task_struct *next, unsigned long prev_state)
> +{
> +	return 0;
> +}

I think this tracepoint is never attached. You can verify it by adding a
bpf_printk("hello") here and check if you see any message in
/sys/kernel/tracing/trace_pipe.

To attach this TP you need to do something like this:

diff --git a/tools/testing/selftests/sched_ext/maximal.c b/tools/testing/selftests/sched_ext/maximal.c
index c6be50a9941d5..1dc3692246705 100644
--- a/tools/testing/selftests/sched_ext/maximal.c
+++ b/tools/testing/selftests/sched_ext/maximal.c
@@ -19,6 +19,9 @@ static enum scx_test_status setup(void **ctx)
 	SCX_ENUM_INIT(skel);
 	SCX_FAIL_IF(maximal__load(skel), "Failed to load skel");
 
+	bpf_map__set_autoattach(skel->maps.maximal_ops, false);
+	SCX_FAIL_IF(maximal__attach(skel), "Failed to attach skel");
+
 	*ctx = skel;
 
 	return SCX_TEST_PASS;
diff --git a/tools/testing/selftests/sched_ext/reload_loop.c b/tools/testing/selftests/sched_ext/reload_loop.c
index 308211d804364..49297b83d748d 100644
--- a/tools/testing/selftests/sched_ext/reload_loop.c
+++ b/tools/testing/selftests/sched_ext/reload_loop.c
@@ -23,6 +23,9 @@ static enum scx_test_status setup(void **ctx)
 	SCX_ENUM_INIT(skel);
 	SCX_FAIL_IF(maximal__load(skel), "Failed to load skel");
 
+	bpf_map__set_autoattach(skel->maps.maximal_ops, false);
+	SCX_FAIL_IF(maximal__attach(skel), "Failed to attach skel");
+
 	return SCX_TEST_PASS;
 }
 
>  
>  void BPF_STRUCT_OPS(maximal_cpu_online, s32 cpu)
>  {}
> @@ -150,8 +149,6 @@ struct sched_ext_ops maximal_ops = {
>  	.set_weight		= (void *) maximal_set_weight,
>  	.set_cpumask		= (void *) maximal_set_cpumask,
>  	.update_idle		= (void *) maximal_update_idle,
> -	.cpu_acquire		= (void *) maximal_cpu_acquire,
> -	.cpu_release		= (void *) maximal_cpu_release,
>  	.cpu_online		= (void *) maximal_cpu_online,
>  	.cpu_offline		= (void *) maximal_cpu_offline,
>  	.init_task		= (void *) maximal_init_task,
> -- 
> 2.48.1
> 

Thanks,
-Andrea