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From: John Stultz <jstultz@google.com>
Date: Mon, 1 Apr 2024 16:34:21 -0700
Message-ID: <CANDhNCrW6LrXecRa0gXRhxhthzNeLkfx+UaYq-NgtQtqdsHw0w@mail.gmail.com>
Subject: Re: [PATCH v9 7/7] sched: Split scheduler and execution contexts
To: Metin Kaya <metin.kaya@arm.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Peter Zijlstra <peterz@infradead.org>, 
	Joel Fernandes <joelaf@google.com>, Qais Yousef <qyousef@google.com>, Ingo Molnar <mingo@redhat.com>, 
	Juri Lelli <juri.lelli@redhat.com>, Vincent Guittot <vincent.guittot@linaro.org>, 
	Dietmar Eggemann <dietmar.eggemann@arm.com>, Valentin Schneider <vschneid@redhat.com>, 
	Steven Rostedt <rostedt@goodmis.org>, Ben Segall <bsegall@google.com>, 
	Zimuzo Ezeozue <zezeozue@google.com>, Youssef Esmat <youssefesmat@google.com>, 
	Mel Gorman <mgorman@suse.de>, Daniel Bristot de Oliveira <bristot@redhat.com>, Will Deacon <will@kernel.org>, 
	Waiman Long <longman@redhat.com>, Boqun Feng <boqun.feng@gmail.com>, 
	"Paul E. McKenney" <paulmck@kernel.org>, Xuewen Yan <xuewen.yan94@gmail.com>, 
	K Prateek Nayak <kprateek.nayak@amd.com>, Thomas Gleixner <tglx@linutronix.de>, kernel-team@android.com, 
	"Connor O'Brien" <connoro@google.com>
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On Mon, Mar 18, 2024 at 8:06=E2=80=AFAM Metin Kaya <metin.kaya@arm.com> wro=
te:
> On 15/03/2024 4:39 am, John Stultz wrote:
> > From: Peter Zijlstra <peterz@infradead.org>
> >
> > Let's define the scheduling context as all the scheduler state
> > in task_struct for the task selected to run, and the execution
> > context as all state required to actually run the task.
> >
> > Currently both are intertwined in task_struct. We want to
> > logically split these such that we can use the scheduling
> > context of the task selected to be scheduled, but use the
> > execution context of a different task to actually be run.
> >
> > To this purpose, introduce rq_selected() macro to point to the
> > task_struct selected from the runqueue by the scheduler, and
> > will be used for scheduler state, and preserve rq->curr to
> > indicate the execution context of the task that will actually be
> > run.
> >
> > Cc: Joel Fernandes <joelaf@google.com>
> > Cc: Qais Yousef <qyousef@google.com>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Juri Lelli <juri.lelli@redhat.com>
> > Cc: Vincent Guittot <vincent.guittot@linaro.org>
> > Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
> > Cc: Valentin Schneider <vschneid@redhat.com>
> > Cc: Steven Rostedt <rostedt@goodmis.org>
> > Cc: Ben Segall <bsegall@google.com>
> > Cc: Zimuzo Ezeozue <zezeozue@google.com>
> > Cc: Youssef Esmat <youssefesmat@google.com>
> > Cc: Mel Gorman <mgorman@suse.de>
> > Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
> > Cc: Will Deacon <will@kernel.org>
> > Cc: Waiman Long <longman@redhat.com>
> > Cc: Boqun Feng <boqun.feng@gmail.com>
> > Cc: "Paul E. McKenney" <paulmck@kernel.org>
> > Cc: Xuewen Yan <xuewen.yan94@gmail.com>
> > Cc: K Prateek Nayak <kprateek.nayak@amd.com>
> > Cc: Metin Kaya <Metin.Kaya@arm.com>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: kernel-team@android.com
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>
> Duplicate S-o-b for Peter.

Yes, though I believe this accurately tracks the path of development.

The patch originally by Peter was sent by Juri:
  https://lore.kernel.org/all/20181009092434.26221-5-juri.lelli@redhat.com/

Then and Peter put it in a branch on his git tree(adding another SoB
and the Link tag), from which Conor picked it up:
  https://lore.kernel.org/lkml/20221003214501.2050087-6-connoro@google.com/

Followed by me.

That said, I can no longer find the branch in Peter's tree, so it's
possible I have this history wrong, but this is what I recall.

So I'm hesitant to change that part of the attribution, unless Peter
requests otherwise.

thanks
-john