[PATCH 05/17] sched_ext: Relocate cpu_acquire/cpu_release to end of struct sched_ext_ops

Tejun Heo
2026-04-28T20:35:52Z

cpu_acquire and cpu_release are deprecated and slated for removal. Move
their declarations to the end of struct sched_ext_ops so an upcoming
cid-form struct (sched_ext_ops_cid) can omit them entirely without
disturbing the offsets of the shared fields.

Switch the two SCX_HAS_OP() callers for these ops to direct field checks
since the relocated ops sit outside the SCX_OPI_END range covered by the
has_op bitmap.

scx_kf_allow_flags[] auto-sizes to the highest used SCX_OP_IDX, so
SCX_OP_IDX(cpu_release) moving to a higher index just enlarges the
sparse array; the lookup logic is unchanged.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
---
kernel/sched/ext.c | 4 +--
kernel/sched/ext_internal.h | 54 ++++++++++++++++++++++---------------
2 files changed, 34 insertions(+), 24 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index e9cf9d8f4626..b197da2b960d 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -2823,7 +2823,7 @@ 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(sch, cpu_acquire))
+ if (sch->ops.cpu_acquire)
SCX_CALL_OP(sch, cpu_acquire, rq, cpu, NULL);
rq->scx.cpu_released = false;
}
@@ -2969,7 +2969,7 @@ static void switch_class(struct rq *rq, struct task_struct *next)
* next time that balance_one() is invoked.
*/
if (!rq->scx.cpu_released) {
- if (SCX_HAS_OP(sch, cpu_release)) {
+ if (sch->ops.cpu_release) {
struct scx_cpu_release_args args = {
.reason = preempt_reason_from_class(next_class),
.task = next,
diff --git a/kernel/sched/ext_internal.h b/kernel/sched/ext_internal.h
index d4960df23da4..919d4aa08656 100644
--- a/kernel/sched/ext_internal.h
+++ b/kernel/sched/ext_internal.h
@@ -523,28 +523,6 @@ struct sched_ext_ops {
*/
void (*update_idle)(s32 cpu, bool idle);

- /**
- * @cpu_acquire: A CPU is becoming available to the BPF scheduler
- * @cpu: The CPU being acquired by the BPF scheduler.
- * @args: Acquire arguments, see the struct definition.
- *
- * A CPU that was previously released from the BPF scheduler is now once
- * again under its control.
- */
- void (*cpu_acquire)(s32 cpu, struct scx_cpu_acquire_args *args);
-
- /**
- * @cpu_release: A CPU is taken away from the BPF scheduler
- * @cpu: The CPU being released by the BPF scheduler.
- * @args: Release arguments, see the struct definition.
- *
- * The specified CPU is no longer under the control of the BPF
- * scheduler. This could be because it was preempted by a higher
- * priority sched_class, though there may be other reasons as well. The
- * caller should consult @args->reason to determine the cause.
- */
- void (*cpu_release)(s32 cpu, struct scx_cpu_release_args *args);
-
/**
* @init_task: Initialize a task to run in a BPF scheduler
* @p: task to initialize for BPF scheduling
@@ -835,6 +813,38 @@ struct sched_ext_ops {

/* internal use only, must be NULL */
void __rcu *priv;
+
+ /*
+ * Deprecated callbacks. Kept at the end of the struct so the cid-form
+ * struct (sched_ext_ops_cid) can omit them without affecting the
+ * shared field offsets. Use SCX_ENQ_IMMED instead. Sitting past
+ * SCX_OPI_END means has_op doesn't cover them, so SCX_HAS_OP() cannot
+ * be used; callers must test sch->ops.cpu_acquire / cpu_release
+ * directly.
+ */
+
+ /**
+ * @cpu_acquire: A CPU is becoming available to the BPF scheduler
+ * @cpu: The CPU being acquired by the BPF scheduler.
+ * @args: Acquire arguments, see the struct definition.
+ *
+ * A CPU that was previously released from the BPF scheduler is now once
+ * again under its control. Deprecated; use SCX_ENQ_IMMED instead.
+ */
+ void (*cpu_acquire)(s32 cpu, struct scx_cpu_acquire_args *args);
+
+ /**
+ * @cpu_release: A CPU is taken away from the BPF scheduler
+ * @cpu: The CPU being released by the BPF scheduler.
+ * @args: Release arguments, see the struct definition.
+ *
+ * The specified CPU is no longer under the control of the BPF
+ * scheduler. This could be because it was preempted by a higher
+ * priority sched_class, though there may be other reasons as well. The
+ * caller should consult @args->reason to determine the cause.
+ * Deprecated; use SCX_ENQ_IMMED instead.
+ */
+ void (*cpu_release)(s32 cpu, struct scx_cpu_release_args *args);
};

enum scx_opi {
--
2.54.0