Hi,
On Sat, Jun 06, 2015 at 06:53:22PM +0800, Simon Guo wrote:
> Dear alias,
>
> I noticed there is a time_slice variable for SCHED_RR policy in
> task_struct.rt member (I am using 4.1.0 kernel):
> struct sched_rt_entity {
> ...
> unsigned int time_slice;
> ...
> };
>
> Per my understanding, the task_struct.rt.time_slice should be
> initialized to sched_rr_timeslice or RR_TIMESLICE . Like what process 0 has done:
> #define INIT_TASK(tsk) \
> {
> ...
> .rt = { \
> .run_list = LIST_HEAD_INIT(tsk.rt.run_list), \
> .time_slice = RR_TIMESLICE, \
> },
> ...
> }
>
> However I didn't see somewhere in copy_process() to set time_slice
> value for a new forked SCHED_RR process.
>
> If time_slice is not initialized, time_slice will be with value 0 and
> will be overflow to a big value in following "if (--p->rt.time_slice)" statement:
> static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
> {
> ...
> /*
> * RR tasks need a special form of timeslice management.
> * FIFO tasks have no timeslices.
> */
> if (p->policy != SCHED_RR)
> return;
>
> if (--p->rt.time_slice)
> return;
>
> p->rt.time_slice = sched_rr_timeslice;
> ...
> }
>
> Is it a bug? Please correct me if I am wrong.
Looks the initialization logic is in arch_dup_task_struct(). Please
ignore my previous question.
Thanks,
Simon
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