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From: "Paul E. McKenney" <paulmck@kernel.org>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Josh Triplett <josh@joshtriplett.org>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Neeraj Upadhyay <neeraju@codeaurora.org>,
	rcu <rcu@vger.kernel.org>, Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH 2/2] rcu/tree: Clarify comments about FQS loop reporting quiescent states
Date: Thu, 30 Jul 2020 09:35:20 -0700
Message-ID: <20200730163520.GA9247@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <CAEXW_YSbad9Cium_9f1eA1RfZ2Me9JcX2S-KMe-jRQo8W6AaBg@mail.gmail.com>

On Wed, Jul 29, 2020 at 11:25:19PM -0400, Joel Fernandes wrote:
> On Wed, Jul 29, 2020 at 11:02 PM Joel Fernandes (Google)
> <joel@joelfernandes.org> wrote:
> >
> > At least since v4.19, the FQS loop no longer reports quiescent states
> 
> I meant here, "FQS loop no longer reports quiescent states for offline CPUs."
> 
> Sorry,

You did have me going there for a bit.  ;-)

No period (".") at the end though, unless you fix up the following
to start a new sentence.

> > unless it is a dire situation where an offlined CPU failed to report
> > a quiescent state. Let us clarify the comment in rcu_gp_init() inorder
> > to keep the comment current.

How about the following for this last sentence?

"This commit therefore fixes the comment in rcu_gp_init() to match
the current code."

> > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> > ---
> >  kernel/rcu/tree.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index 1e51962b565b..929568ff5989 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -1701,8 +1701,8 @@ static bool rcu_gp_init(void)
> >
> >         /*
> >          * Apply per-leaf buffered online and offline operations to the
> > -        * rcu_node tree.  Note that this new grace period need not wait
> > -        * for subsequent online CPUs, and that quiescent-state forcing
> > +        * rcu_node tree.  Note that this new grace period need not wait for
> > +        * subsequent online CPUs, and that RCU hooks in CPU offlining path
> >          * will handle subsequent offline CPUs.

How about something like this?

	...  Note that this new grace period ned not wait for subsequent
	online CPUs, and that RCU hooks in the CPU offlining path, when
	combined with checks in this function, will handle CPUs that
	are currently going offline and that go offline later.

						Thanx, Paul

> >          */
> >         rcu_state.gp_state = RCU_GP_ONOFF;
> > --
> > 2.28.0.rc0.142.g3c755180ce-goog
> >

  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30  3:02 [PATCH 1/2] rcu/tree: Add a warning if CPU being onlined did not report QS already Joel Fernandes (Google)
2020-07-30  3:02 ` [PATCH 2/2] rcu/tree: Clarify comments about FQS loop reporting quiescent states Joel Fernandes (Google)
2020-07-30  3:25   ` Joel Fernandes
2020-07-30 16:35     ` Paul E. McKenney [this message]
2020-07-31  1:21       ` Joel Fernandes
2020-07-31  1:34         ` Paul E. McKenney
2020-07-30 16:21 ` [PATCH 1/2] rcu/tree: Add a warning if CPU being onlined did not report QS already Paul E. McKenney
2020-07-31  1:08   ` Joel Fernandes
2020-07-31  1:42   ` Joel Fernandes
2020-07-31  3:48     ` Paul E. McKenney
2020-08-07 15:37       ` Joel Fernandes
2020-08-07 15:45         ` Joel Fernandes

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