On Mon, Apr 4, 2011 at 4:13 PM, Laurențiu Dascălu <dascalu.laurentziu@gmail.com> wrote:
Hello,
I'm trying to implement a simple scheduling policy in the Linux kernel, but I'm not sure if I correctly understand the sched_class interface. Specifically, I would like to know more about the following functions:
There's some useful information about sched_class interface inside [1], check 'Scheduler Classes', page 89.
* put_prev_task(struct rq *rq, struct task_struct *prev) Q: It means the prev was preempted and I have to reschedule another task? Or I have just to add prev to the running queue?
put_prev_task first announces to the scheduler class that the currently running task is going to be replaced by another one. So I guess, that prev was preempted but it is still in the running queue. Now the scheduler has to dequeue it, and to schedule another task.
The code should look something like:
if (prev->se.on_rq) { enqueue_task(rq, prev); }
or I'm wrong?
Why do you want to enqueue prev? Isn't rq supposed to hold the current running tasks?
* task_tick(struct rq *rq, struct task_struct *p, int queued) Q: Should I preempt the task p, by calling resched_task? What does "queued" means?
thanks, Daniel. [1] Professional Linux Kernel Architecture, W. Mauerer