sched_ext: Rename scx_bpf_dispatch[_vtime]_from_dsq*() -> scx_bpf_dsq_move[_vtime]*()

In sched_ext API, a repeatedly reported pain point is the overuse of the
verb "dispatch" and confusion around "consume":

- ops.dispatch()
- scx_bpf_dispatch[_vtime]()
- scx_bpf_consume()
- scx_bpf_dispatch[_vtime]_from_dsq*()

This overloading of the term is historical. Originally, there were only
built-in DSQs and moving a task into a DSQ always dispatched it for
execution. Using the verb "dispatch" for the kfuncs to move tasks into these
DSQs made sense.

Later, user DSQs were added and scx_bpf_dispatch[_vtime]() updated to be
able to insert tasks into any DSQ. The only allowed DSQ to DSQ transfer was
from a non-local DSQ to a local DSQ and this operation was named "consume".
This was already confusing as a task could be dispatched to a user DSQ from
ops.enqueue() and then the DSQ would have to be consumed in ops.dispatch().
Later addition of scx_bpf_dispatch_from_dsq*() made the confusion even worse
as "dispatch" in this context meant moving a task to an arbitrary DSQ from a
user DSQ.

Clean up the API with the following renames:

1. scx_bpf_dispatch[_vtime]()		-> scx_bpf_dsq_insert[_vtime]()
2. scx_bpf_consume()			-> scx_bpf_dsq_move_to_local()
3. scx_bpf_dispatch[_vtime]_from_dsq*()	-> scx_bpf_dsq_move[_vtime]*()

This patch performs the third set of renames. Compatibility is maintained
by:

- The previous kfunc names are still provided by the kernel so that old
  binaries can run. Kernel generates a warning when the old names are used.

- compat.bpf.h provides wrappers for the new names which automatically fall
  back to the old names when running on older kernels. They also trigger
  build error if old names are used for new builds.

- scx_bpf_dispatch[_vtime]_from_dsq*() were already wrapped in __COMPAT
  macros as they were introduced during v6.12 cycle. Wrap new API in
  __COMPAT macros too and trigger build errors on both __COMPAT prefixed and
  naked usages of the old names.

The compat features will be dropped after v6.15.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Andrea Righi <arighi@nvidia.com>
Acked-by: Changwoo Min <changwoo@igalia.com>
Acked-by: Johannes Bechberger <me@mostlynerdless.de>
Acked-by: Giovanni Gherdovich <ggherdovich@suse.com>
Cc: Dan Schatzberg <dschatzberg@meta.com>
Cc: Ming Yang <yougmark94@gmail.com>

1 files changed, 10 insertions, 10 deletions

diff --git a/tools/sched_ext/scx_qmap.bpf.c b/tools/sched_ext/scx_qmap.bpf.c
index 08f121252c56..ee264947e0c3 100644
--- a/tools/sched_ext/scx_qmap.bpf.c
+++ b/tools/sched_ext/scx_qmap.bpf.c
@@ -294,10 +294,10 @@ static void update_core_sched_head_seq(struct task_struct *p)
 }
 
 /*
- * To demonstrate the use of scx_bpf_dispatch_from_dsq(), implement silly
- * selective priority boosting mechanism by scanning SHARED_DSQ looking for
- * highpri tasks, moving them to HIGHPRI_DSQ and then consuming them first. This
- * makes minor difference only when dsp_batch is larger than 1.
+ * To demonstrate the use of scx_bpf_dsq_move(), implement silly selective
+ * priority boosting mechanism by scanning SHARED_DSQ looking for highpri tasks,
+ * moving them to HIGHPRI_DSQ and then consuming them first. This makes minor
+ * difference only when dsp_batch is larger than 1.
  *
  * scx_bpf_dispatch[_vtime]_from_dsq() are allowed both from ops.dispatch() and
  * non-rq-lock holding BPF programs. As demonstration, this function is called
@@ -318,11 +318,11 @@ static bool dispatch_highpri(bool from_timer)
 
 		if (tctx->highpri) {
 			/* exercise the set_*() and vtime interface too */
-			__COMPAT_scx_bpf_dispatch_from_dsq_set_slice(
+			__COMPAT_scx_bpf_dsq_move_set_slice(
 				BPF_FOR_EACH_ITER, slice_ns * 2);
-			__COMPAT_scx_bpf_dispatch_from_dsq_set_vtime(
+			__COMPAT_scx_bpf_dsq_move_set_vtime(
 				BPF_FOR_EACH_ITER, highpri_seq++);
-			__COMPAT_scx_bpf_dispatch_vtime_from_dsq(
+			__COMPAT_scx_bpf_dsq_move_vtime(
 				BPF_FOR_EACH_ITER, p, HIGHPRI_DSQ, 0);
 		}
 	}
@@ -340,9 +340,9 @@ static bool dispatch_highpri(bool from_timer)
 		else
 			cpu = scx_bpf_pick_any_cpu(p->cpus_ptr, 0);
 
-		if (__COMPAT_scx_bpf_dispatch_from_dsq(BPF_FOR_EACH_ITER, p,
-						       SCX_DSQ_LOCAL_ON | cpu,
-						       SCX_ENQ_PREEMPT)) {
+		if (__COMPAT_scx_bpf_dsq_move(BPF_FOR_EACH_ITER, p,
+					      SCX_DSQ_LOCAL_ON | cpu,
+					      SCX_ENQ_PREEMPT)) {
 			if (cpu == this_cpu) {
 				dispatched = true;
 				__sync_fetch_and_add(&nr_expedited_local, 1);