On 24/07/2020 17:31, Daniel Bristot de Oliveira wrote:
> On 7/24/20 9:14 AM, Juri Lelli wrote:
>> 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".
>
> Looks good to me!
>
> Acked-by: Daniel Bristot de Oliveira <bris...@redhat.com>
Yes, makes sense to me!
Reviewed-by: Dietmar Eggemann <dietmar.eggem...@arm.com>
