Hi,
On 07/07/20 00:04, Peng Liu wrote:
> 'commit 840d719604b0 ("sched/deadline: Update rq_clock of later_rq when
> pushing a task")'
> introduced the update_rq_clock() to fix the "used-before-update" bug.
>
> 'commit f4904815f97a ("sched/deadline: Fix double accounting of rq/running bw
> in push & pull")'
> took away the bug source(add_running_bw()).
>
> We no longer need to update rq_clock in advance, let activate_task()
> worry about that.
>
> Signed-off-by: Peng Liu <iwtba...@gmail.com>
> ---
> kernel/sched/deadline.c | 8 +-------
> 1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 504d2f51b0d6..c3fa11f84d93 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -2104,13 +2104,7 @@ static int push_dl_task(struct rq *rq)
>
> deactivate_task(rq, next_task, 0);
> set_task_cpu(next_task, later_rq->cpu);
> -
> - /*
> - * Update the later_rq clock here, because the clock is used
> - * by the cpufreq_update_util() inside __add_running_bw().
> - */
> - update_rq_clock(later_rq);
> - activate_task(later_rq, next_task, ENQUEUE_NOCLOCK);
> + activate_task(later_rq, next_task, 0);
> ret = 1;
The change looks good to me, since now add_running_bw() is called later
by enqueue_task_dl(), but rq_clock has already been updated by core's
enqueue_task().
Daniel, Dietmar, a second pair of eyes (since you authored the commits
above)?
I'd chage subject to something like "sched/deadline: Stop updating
rq_clock before pushing a task".
Thanks,
Juri
