linux-kernel - Re: [PATCH v2] psi: Fix avg trigger being fired unexpectedly.

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Date: Thu, 18 Apr 2024 10:15:21 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: "levi.yun" <ppbuk5246@...il.com>, hannes@...xchg.org, peterz@...radead.org, 
	mingo@...hat.com, juri.lelli@...hat.com, vincent.guittot@...aro.org, 
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com, 
	mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] psi: Fix avg trigger being fired unexpectedly.

On Tue, Mar 26, 2024 at 10:49 AM Suren Baghdasaryan <surenb@...gle.com> wrote:
>
> On Tue, Mar 12, 2024 at 6:10 AM levi.yun <ppbuk5246@...il.com> wrote:
> >
> > Gentle ping..
> >
> > On Mon, Feb 26, 2024 at 09:12:37PM +0000, Levi Yun wrote:
> > > commit 915a087e4c473("psi: Fix trigger being fired unexpectedly at initial")
> > > fixes unexpected event fired when group->total accumulated for PSI_POLL.
> > > But, for PSI_AVGS, win->value should be initialized with group->total[PSI_AVGS].
> > > Moreover, to get exact initial value for win->value, it should be set
> > > under each trigger lock to avoid concurrent changes to group->total[].
> > >
> > > Signed-off-by: Levi Yun <ppbuk5246@...il.com>
> > > Acked-by: Suren Baghdasaryan <surenb@...gle.com>
>
> Hi Peter,
> Could you please pull this patch into your tree? I don't see it in any
> tree, so I think you missed it.

I heard Peter is currently unavailable. Ingo, would you please take
this patch into the scheduler tree?
Thanks,
Suren.

> Thanks,
> Suren.
>
> > > ---
> > > v2: Fix commit message.
> > > ---
> > >  kernel/sched/psi.c | 8 +++++---
> > >  1 file changed, 5 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> > > index 7b4aa5809c0f..e7f66ab2ad3e 100644
> > > --- a/kernel/sched/psi.c
> > > +++ b/kernel/sched/psi.c
> > > @@ -1323,9 +1323,6 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, char *buf,
> > >       t->state = state;
> > >       t->threshold = threshold_us * NSEC_PER_USEC;
> > >       t->win.size = window_us * NSEC_PER_USEC;
> > > -     window_reset(&t->win, sched_clock(),
> > > -                     group->total[PSI_POLL][t->state], 0);
> > > -
> > >       t->event = 0;
> > >       t->last_event_time = 0;
> > >       t->of = of;
> > > @@ -1336,6 +1333,8 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, char *buf,
> > >
> > >       if (privileged) {
> > >               mutex_lock(&group->rtpoll_trigger_lock);
> > > +             window_reset(&t->win, sched_clock(),
> > > +                             group->total[PSI_POLL][t->state], 0);
> > >
> > >               if (!rcu_access_pointer(group->rtpoll_task)) {
> > >                       struct task_struct *task;
> > > @@ -1361,6 +1360,9 @@ struct psi_trigger *psi_trigger_create(struct psi_group *group, char *buf,
> > >       } else {
> > >               mutex_lock(&group->avgs_lock);
> > >
> > > +             window_reset(&t->win, sched_clock(),
> > > +                             group->total[PSI_AVGS][t->state], 0);
> > > +
> > >               list_add(&t->node, &group->avg_triggers);
> > >               group->avg_nr_triggers[t->state]++;
> > >
> > > --
> > > 2.39.2