linux-kernel - Re: [PATCH v2] srcu: Improve comments about acceleration leak

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Message-ID: <ZYC5iAds0sJuDYzd@localhost.localdomain>
Date: Mon, 18 Dec 2023 22:28:40 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: Joel Fernandes <joel@...lfernandes.org>
Cc: linux-kernel@...r.kernel.org, Lai Jiangshan <jiangshanlai@...il.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Josh Triplett <josh@...htriplett.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Neeraj Upadhyay <neeraj.iitr10@...il.com>, rcu@...r.kernel.org
Subject: Re: [PATCH v2] srcu: Improve comments about acceleration leak

Le Mon, Dec 18, 2023 at 10:27:56AM -0500, Joel Fernandes a écrit :
> On Mon, Dec 18, 2023 at 7:13 AM Frederic Weisbecker <frederic@...nel.org> wrote:
> >
> > Le Sun, Dec 17, 2023 at 09:00:15PM -0500, Joel Fernandes a écrit :
> > > "Acceleration can never fail because the state of gp_seq value used
> > > for acceleration is <= the state of gp_seq used for advancing."
> > >
> > > Does that sound correct now?
> >
> > That can be confusing since acceleration relies on rcu_seq_snap() while
> > advance relies on rcu_seq_current(). And rcu_seq_snap() returns a snapshot
> > that may be above the subsequent rcu_seq_current() return value.
> >
> > So it should rather be something like:
> >
> > "The base current gp_seq value used to produce the snapshot has to
> > be <= the gp_seq used for advancing."
> 
> Yeah "base current gp_seq" though probably equally confusing sounds a
> bit better, so I'll just use that instead of "state of gp_seq".
> 
> With that can I add your Review tag?

Sure, sounds good!

Thanks.

> 
>  - Joel
>