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McKenney" To: Valentin Schneider Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, x86@kernel.org, rcu@vger.kernel.org, linux-kselftest@vger.kernel.org, Steven Rostedt , Masami Hiramatsu , Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Paolo Bonzini , Wanpeng Li , Vitaly Kuznetsov , Andy Lutomirski , Peter Zijlstra , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Josh Poimboeuf , Jason Baron , Kees Cook , Sami Tolvanen , Ard Biesheuvel , Nicholas Piggin , Juerg Haefliger , Nicolas Saenz Julienne , "Kirill A. Shutemov" , Nadav Amit , Dan Carpenter , Chuang Wang , Yang Jihong , Petr Mladek , "Jason A. Donenfeld" , Song Liu , Julian Pidancet , Tom Lendacky , Dionna Glaze , Thomas =?iso-8859-1?Q?Wei=DFschuh?= , Juri Lelli , Daniel Bristot de Oliveira , Marcelo Tosatti , Yair Podemsky Subject: Re: [RFC PATCH v2 16/20] rcu: Make RCU dynticks counter size configurable Message-ID: <28d4abb7-8496-45ec-b270-ea2b6164537b@paulmck-laptop> Reply-To: paulmck@kernel.org References: <20230720163056.2564824-1-vschneid@redhat.com> <20230720163056.2564824-17-vschneid@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 09004140010 X-Rspam-User: X-Stat-Signature: s1dbipfhyxo7tff5hioewag6ynsiuo6b X-Rspamd-Server: rspam03 X-HE-Tag: 1689948605-811539 X-HE-Meta: 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 W9xROyvF 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jul 21, 2023 at 09:17:53AM +0100, Valentin Schneider wrote: > On 20/07/23 17:30, Valentin Schneider wrote: > > index bdd7eadb33d8f..1ff2aab24e964 100644 > > --- a/kernel/rcu/Kconfig > > +++ b/kernel/rcu/Kconfig > > @@ -332,4 +332,37 @@ config RCU_DOUBLE_CHECK_CB_TIME > > Say Y here if you need tighter callback-limit enforcement. > > Say N here if you are unsure. > > > > +config RCU_DYNTICKS_RANGE_BEGIN > > + int > > + depends on !RCU_EXPERT > > + default 31 if !CONTEXT_TRACKING_WORK > > You'll note that this should be 30 really, because the lower *2* bits are > taken by the context state (CONTEXT_GUEST has a value of 3). > > This highlights the fragile part of this: the Kconfig values are hardcoded, > but they depend on CT_STATE_SIZE, CONTEXT_MASK and CONTEXT_WORK_MAX. The > static_assert() will at least capture any misconfiguration, but having that > enforced by the actual Kconfig ranges would be less awkward. > > Do we currently have a way of e.g. making a Kconfig file depend on and use > values generated by a C header? Why not just have something like a boolean RCU_DYNTICKS_TORTURE Kconfig option and let the C code work out what the number of bits should be? I suppose that there might be a failure whose frequency depended on the number of bits, which might be an argument for keeping something like RCU_DYNTICKS_RANGE_BEGIN for fault isolation. But still using RCU_DYNTICKS_TORTURE for normal testing. Thoughts? Thanx, Paul