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

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Message-Id: <20180621150547.GF3593@linux.vnet.ibm.com>
Date:   Thu, 21 Jun 2018 08:05:47 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Byungchul Park <byungchul.park@....com>
Cc:     Byungchul Park <max.byungchul.park@...il.com>,
        jiangshanlai@...il.com, josh@...htriplett.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        linux-kernel@...r.kernel.org, kernel-team@....com,
        Joel Fernandes <joel@...lfernandes.org>, luto@...nel.org
Subject: Re: [RFC 2/2] rcu: Remove ->dynticks_nmi_nesting from struct
 rcu_dynticks

On Thu, Jun 21, 2018 at 07:08:30PM +0900, Byungchul Park wrote:
> On Thu, Jun 21, 2018 at 03:39:49PM +0900, Byungchul Park wrote:
> 
> [...]
> 
> > I applied what you suggested and re-named rcu_nmi_{enter,exit} to
>                                                ^
>                         rcu_nmi_{enter,exit}_common(bool irq)
> 
> > rcu_irq_{enter,exit} and applied the same re-naming to
>           ^
>      rcu_irq_{enter,exit}_common(bool nmi)
> 
> > ->dynticks_nmi_nesting as well, since those are not things to do with
>            ^
>     dynticks_nmi_nesting -> dynticks_irq_nesting
> 
> > nmi anymore but both irq and nmi.
> > 
> > I think "irq" is better to represent both irq and nmi than "nmi".
> > Please let me know if you don't think so. I can get rid of the re-
> > naming from the patch.

Again, we need to keep "nmi".  There is a lot of irq-safe code in the
Linux kernel, but not so much nmi-safe code, so we need to give the
reader as many hints as we can that this code is unusual.

							Thanx, Paul