linux-kernel - Re: [RFC 2/2] rcu: Remove ->dynticks_nmi_nesting from struct rcu

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Date:   Mon, 25 Jun 2018 16:30:39 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Andrew Lutomirski <luto@...nel.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        joel@...lfernandes.org, Byungchul Park <byungchul.park@....com>,
        byungchul park <max.byungchul.park@...il.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        LKML <linux-kernel@...r.kernel.org>, kernel-team@....com
Subject: Re: [RFC 2/2] rcu: Remove ->dynticks_nmi_nesting from struct rcu_dynticks

On Mon, Jun 25, 2018 at 3:16 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Mon, 25 Jun 2018 13:47:45 -0700
> Andy Lutomirski <luto@...nel.org> wrote:
>
> >
> > As a straightforward example, NMI and MCE can nest inside each other.
>
> But I'm not sure how stable the machine becomes when MCE's start
> interrupting NMIs. Also, can MCE callbacks use RCU?
>
> > IIRC we treat #DB somewhat NMI-ish-ly as well.
>
> And #DB is something I think we finally said shouldn't be done in NMIs,
> IIRC.
>

No one ever applied the patch to make it so, so we still support it.