From: Andrea Righi Date: Mon, 9 Jun 2025 16:23:42 +0000 (+0200) Subject: sched_ext: Documentation: Clarify time slice handling in task lifecycle X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9465f44d2df21b43f062de303e59e2b391eeab16;p=thirdparty%2Flinux.git sched_ext: Documentation: Clarify time slice handling in task lifecycle It is not always obvious how a task's time slice can be refilled, either explicitly from ops.dispatch() or automatically by the sched_ext core, to skip subsequent ops.enqueue() and ops.dispatch() calls. This typically happens when the task is the only one running on a CPU. To make this behavior easier to understand, update the task lifecycle diagram to explicitly document how time slice handling works in such cases. Signed-off-by: Andrea Righi Signed-off-by: Tejun Heo --- diff --git a/Documentation/scheduler/sched-ext.rst b/Documentation/scheduler/sched-ext.rst index a1869c38046ed..404fe6126a769 100644 --- a/Documentation/scheduler/sched-ext.rst +++ b/Documentation/scheduler/sched-ext.rst @@ -313,16 +313,21 @@ by a sched_ext scheduler: ops.runnable(); /* Task becomes ready to run */ while (task is runnable) { - if (task is not in a DSQ) { + if (task is not in a DSQ && task->scx.slice == 0) { ops.enqueue(); /* Task can be added to a DSQ */ - /* A CPU becomes available */ + /* Any usable CPU becomes available */ ops.dispatch(); /* Task is moved to a local DSQ */ } ops.running(); /* Task starts running on its assigned CPU */ - ops.tick(); /* Called every 1/HZ seconds */ + while (task->scx.slice > 0 && task is runnable) + ops.tick(); /* Called every 1/HZ seconds */ ops.stopping(); /* Task stops running (time slice expires or wait) */ + + /* Task's CPU becomes available */ + + ops.dispatch(); /* task->scx.slice can be refilled */ } ops.quiescent(); /* Task releases its assigned CPU (wait) */