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SubjectRe: [PATCH linux-next v2 1/4] sched/psi: Change update_triggers() to a 'void' function

* yang.yang29@zte.com.cn <yang.yang29@zte.com.cn> wrote:

> From: Yang Yang <yang.yang29@zte.com.cn>
>
> Update_triggers() always returns now + group->rtpoll_min_period, and the
> return value is only used by psi_rtpoll_work(), so change update_triggers()
> to a void function, let group->rtpoll_next_update = now +
> group->rtpoll_min_period directly.
>
> This will avoid unnecessary function return value passing & simplifies
> the function.
>
> Suggested-by: Suren Baghdasaryan <surenb@google.com>
> Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
> ---
> kernel/sched/psi.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index 1d0f634725a6..fec8aab096a8 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -434,7 +434,7 @@ static u64 window_update(struct psi_window *win, u64 now, u64 value)
> return growth;
> }
>
> -static u64 update_triggers(struct psi_group *group, u64 now, bool *update_total,
> +static void update_triggers(struct psi_group *group, u64 now, bool *update_total,
> enum psi_aggregators aggregator)
> {
> struct psi_trigger *t;
> @@ -503,8 +503,6 @@ static u64 update_triggers(struct psi_group *group, u64 now, bool *update_total,
> /* Reset threshold breach flag once event got generated */
> t->pending_event = false;
> }
> -
> - return now + group->rtpoll_min_period;
> }
>
> static u64 update_averages(struct psi_group *group, u64 now)
> @@ -706,7 +704,8 @@ static void psi_rtpoll_work(struct psi_group *group)
> }
>
> if (now >= group->rtpoll_next_update) {
> - group->rtpoll_next_update = update_triggers(group, now, &update_total, PSI_POLL);
> + group->rtpoll_next_update = now + group->rtpoll_min_period;
> + update_triggers(group, now, &update_total, PSI_POLL);

This step is wrong. The equivalent transformation when removing a return value is:

x = fn(y); // fn(y) returns 'z'

to:

fn(y);
x = z;

not:

x = z;
fn(y);

...

Furthermore, I already applied the correct #1 patch to the scheduler tree, see:

e03dc9fa0663 ("sched/psi: Change update_triggers() to a 'void' function")

... which tree is at:

git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched/core

So please send the remaining patch on top of that.

Thanks,

Ingo

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