linux-kernel - Re: [RFC v1 2/2] rcu/tree: Remove dynticks_nmi

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Message-ID: <20190829160946.GP4125@linux.ibm.com>
Date:   Thu, 29 Aug 2019 09:09:46 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org,
        Frederic Weisbecker <fweisbec@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Josh Triplett <josh@...htriplett.org>, kernel-team@...roid.com,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-doc@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        rcu@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        luto@...nel.org
Subject: Re: [RFC v1 2/2] rcu/tree: Remove dynticks_nmi_nesting counter

On Thu, Aug 29, 2019 at 10:43:55AM -0400, Joel Fernandes wrote:

[ . . . ]

> Paul, do we also nuke rcu_eqs_special_set()?  Currently I don't see anyone
> using it. And also remove the bottom most bit of dynticks?
> 
> Also what happens if a TLB flush broadcast is needed? Do we IPI nohz or idle
> CPUs are the moment?
> 
> All of this was introduced in:
> b8c17e6664c4 ("rcu: Maintain special bits at bottom of ->dynticks counter")

Adding Andy Lutomirski on CC.

Andy, is this going to be used in the near term, or should we just get
rid of it?

							Thanx, Paul