linux-kernel - Re: [PATCH rcu 10/11] srcu: Add FORCE_NEED_SRCU_NMI

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Message-ID: <5449d7d5-198e-4c86-916a-998464c9932a@paulmck-laptop>
Date: Tue, 25 Mar 2025 08:51:05 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Boqun Feng <boqun.feng@...il.com>, rcu@...r.kernel.org,
	Jonathan Corbet <corbet@....net>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,
	Davidlohr Bueso <dave@...olabs.net>, Shuah Khan <shuah@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Huth <thuth@...hat.com>,
	"Borislav Petkov (AMD)" <bp@...en8.de>,
	Ard Biesheuvel <ardb@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Yury Norov <yury.norov@...il.com>,
	Valentin Schneider <vschneid@...hat.com>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH rcu 10/11] srcu: Add FORCE_NEED_SRCU_NMI_SAFE Kconfig for
 testing

On Tue, Mar 25, 2025 at 04:36:23PM +0100, Geert Uytterhoeven wrote:
> Hi Paul,
> 
> On Tue, 25 Mar 2025 at 16:08, Paul E. McKenney <paulmck@...nel.org> wrote:
> > commit 2245ef8605a80726548253d885b4cadd97f69f3b
> > Author: Paul E. McKenney <paulmck@...nel.org>
> > Date:   Tue Mar 25 07:31:45 2025 -0700
> >
> >     srcu: Make FORCE_NEED_SRCU_NMI_SAFE depend on RCU_EXPERT
> >
> >     The FORCE_NEED_SRCU_NMI_SAFE is useful only for those wishing to test
> >     the SRCU code paths that accommodate architectures that do not have
> >     NMI-safe per-CPU operations, that is, those architectures that do not
> >     select the ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option.  As such, this
> >     is a specialized Kconfig option that is not intended for casual users.
> >
> >     This commit therefore hides it behind the RCU_EXPERT Kconfig option.
> >     Given that this new FORCE_NEED_SRCU_NMI_SAFE Kconfig option has no effect
> >     unless the ARCH_HAS_NMI_SAFE_THIS_CPU_OPS Kconfig option is also selected,
> >     it also depends on this Kconfig option.
> >
> >     [ paulmck: Apply Geert Uytterhoeven feedback. ]
> >
> >     Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> >     Closes: https://lore.kernel.org/all/CAMuHMdX6dy9_tmpLkpcnGzxyRbe6qSWYukcPp=H1GzZdyd3qBQ@mail.gmail.com/
> >     Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> >
> > diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
> > index b3f985d41717a..ceaf6594f634c 100644
> > --- a/kernel/rcu/Kconfig
> > +++ b/kernel/rcu/Kconfig
> > @@ -68,6 +68,8 @@ config TREE_SRCU
> >  config FORCE_NEED_SRCU_NMI_SAFE
> >         bool "Force selection of NEED_SRCU_NMI_SAFE"
> >         depends on !TINY_SRCU
> > +       depends on RCU_EXPERT
> > +       depends on ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
> >         select NEED_SRCU_NMI_SAFE
> >         default n
> >         help
> 
> LGTM, so
> Reviewed-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Applied, and thank you very much for both the review and the report!

							Thanx, Paul