sched_ext: Documentation: Add ops.dequeue() to task lifecycle

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.

Signed-off-by: Andrea Righi <arighi@nvidia.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/Documentation/scheduler/sched-ext.rst b/Documentation/scheduler/sched-ext.rst
index 404b4e4c33f7e324fa0ebe328db8aaed48e1a724..9f03650abfeba11b05c584f9d11c8f02b22558d8 100644 (file)
--- 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) */