[PATCH sched_ext/for-7.1] sched_ext: Documentation: Add ops.dequeue() to task lifecycle

Andrea Righi
2026-04-06T11:48:07Z

Document ops.dequeue() in the sched_ext task lifecycle now that its
semantics are well-defined.

Also update the pseudo-code to use task_is_runnable() consistently and
clarify the case where ops.dispatch() does not refill the time slice.

Fixes: ebf1ccff79c4 ("sched_ext: Fix ops.dequeue() semantics")
Signed-off-by: Andrea Righi <arighi@nvidia.com>
---
Documentation/scheduler/sched-ext.rst | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/Documentation/scheduler/sched-ext.rst b/Documentation/scheduler/sched-ext.rst
index 404b4e4c33f7e..9f03650abfeba 100644
--- a/Documentation/scheduler/sched-ext.rst
+++ b/Documentation/scheduler/sched-ext.rst
@@ -422,23 +422,29 @@ by a sched_ext scheduler:

ops.runnable(); /* Task becomes ready to run */

- while (task is runnable) {
+ while (task_is_runnable(task)) {
if (task is not in a DSQ && task->scx.slice == 0) {
ops.enqueue(); /* Task can be added to a DSQ */

- /* Any usable CPU becomes available */
+ /* Task property change (i.e., affinity, nice, etc.)? */
+ if (sched_change(task)) {
+ ops.dequeue(); /* Exiting BPF scheduler custody */
+ continue;
+ }
+ }

- ops.dispatch(); /* Task is moved to a local DSQ */
+ /* Any usable CPU becomes available */
+
+ ops.dispatch(); /* Task is moved to a local DSQ */
+ ops.dequeue(); /* Exiting BPF scheduler custody */

- ops.dequeue(); /* Exiting BPF scheduler */
- }
ops.running(); /* Task starts running on its assigned CPU */

- while task_is_runnable(p) {
- while (task->scx.slice > 0 && task_is_runnable(p))
- ops.tick(); /* Called every 1/HZ seconds */
+ while (task_is_runnable(task) && task->scx.slice > 0) {
+ ops.tick(); /* Called every 1/HZ seconds */

- ops.dispatch(); /* task->scx.slice can be refilled */
+ if (task->scx.slice == 0)
+ ops.dispatch(); /* task->scx.slice can be refilled */
}

ops.stopping(); /* Task stops running (time slice expires or wait) */
--
2.53.0