linux-kernel - Re: [PATCH v10 6/7] sched: Split out __schedule() deactivate task logic into a helper

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Message-ID: <CANDhNCqrPCnNP75_MVA-+B22hrEnc=rwNb+SGdvg61NqedcU2w@mail.gmail.com>
Date: Tue, 4 Jun 2024 12:34:42 -0700
From: John Stultz <jstultz@...gle.com>
To: Qais Yousef <qyousef@...alina.io>
Cc: LKML <linux-kernel@...r.kernel.org>, Joel Fernandes <joelaf@...gle.com>, 
	Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, Valentin Schneider <vschneid@...hat.com>, 
	Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, 
	Zimuzo Ezeozue <zezeozue@...gle.com>, Youssef Esmat <youssefesmat@...gle.com>, 
	Mel Gorman <mgorman@...e.de>, Daniel Bristot de Oliveira <bristot@...hat.com>, Will Deacon <will@...nel.org>, 
	Waiman Long <longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Metin Kaya <Metin.Kaya@....com>, 
	Xuewen Yan <xuewen.yan94@...il.com>, K Prateek Nayak <kprateek.nayak@....com>, 
	Thomas Gleixner <tglx@...utronix.de>, kernel-team@...roid.com
Subject: Re: [PATCH v10 6/7] sched: Split out __schedule() deactivate task
 logic into a helper

On Tue, Jun 4, 2024 at 6:29 AM Qais Yousef <qyousef@...alina.io> wrote:
>
> On 05/06/24 21:54, John Stultz wrote:
> > As we're going to re-use the deactivation logic,
> > split it into a helper.
> >
> > Cc: Joel Fernandes <joelaf@...gle.com>
> > Cc: Qais Yousef <qyousef@...alina.io>
> > Cc: Ingo Molnar <mingo@...hat.com>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Juri Lelli <juri.lelli@...hat.com>
> > Cc: Vincent Guittot <vincent.guittot@...aro.org>
> > Cc: Dietmar Eggemann <dietmar.eggemann@....com>
> > Cc: Valentin Schneider <vschneid@...hat.com>
> > Cc: Steven Rostedt <rostedt@...dmis.org>
> > Cc: Ben Segall <bsegall@...gle.com>
> > Cc: Zimuzo Ezeozue <zezeozue@...gle.com>
> > Cc: Youssef Esmat <youssefesmat@...gle.com>
> > Cc: Mel Gorman <mgorman@...e.de>
> > Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
> > Cc: Will Deacon <will@...nel.org>
> > Cc: Waiman Long <longman@...hat.com>
> > Cc: Boqun Feng <boqun.feng@...il.com>
> > Cc: "Paul E. McKenney" <paulmck@...nel.org>
> > Cc: Metin Kaya <Metin.Kaya@....com>
> > Cc: Xuewen Yan <xuewen.yan94@...il.com>
> > Cc: K Prateek Nayak <kprateek.nayak@....com>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: kernel-team@...roid.com
> > Tested-by: K Prateek Nayak <kprateek.nayak@....com>
> > Tested-by: Metin Kaya <metin.kaya@....com>
> > Reviewed-by: Metin Kaya <metin.kaya@....com>
> > Signed-off-by: John Stultz <jstultz@...gle.com>
> > ---
> > v6:
> > * Define function as static to avoid "no previous prototype"
> >   warnings as Reported-by: kernel test robot <lkp@...el.com>
> > v7:
> > * Rename state task_state to be more clear, as suggested by
> >   Metin Kaya
> > ---
> >  kernel/sched/core.c | 72 +++++++++++++++++++++++++++------------------
> >  1 file changed, 43 insertions(+), 29 deletions(-)
> >
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index 48f0d4b381d5..8bc5844ebab9 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -6572,6 +6572,48 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
> >  # define SM_MASK_PREEMPT     SM_PREEMPT
> >  #endif
> >
> > +/*
> > + * Helper function for __schedule()
> > + *
> > + * If a task does not have signals pending, deactivate it and return true
> > + * Otherwise marks the task's __state as RUNNING and returns false
> > + */
> > +static bool try_to_deactivate_task(struct rq *rq, struct task_struct *p,
> > +                                unsigned long task_state)
> > +{
> > +     if (signal_pending_state(task_state, p)) {
> > +             WRITE_ONCE(p->__state, TASK_RUNNING);
>
> We can avoid extra indention for the other (lengthy) leg if we return here?
>
> The return value is ignored for now, I don't mind keeping it but better call it
> out in the commit message or when you add the new user later you can update the
> signature more easily.

Ah. Good point on both counts here. I've reworked it to use your
suggestions here.

> Generally I think patches 4, 5 and 6 could be sent as their own series with
> minor commit messages tweaks to make them more independent and I hope Ingo and
> Peter are okay to pick them up as they look a nice clean up in general.
>
> Anyway:
>
> Reviewed-by: Qais Yousef <qyousef@...alina.io>

Thanks so much for the review!
-john