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McKenney" , 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 =?utf-8?Q?Wei=C3=9Fschuh?= , Juri Lelli , Daniel Bristot de Oliveira , Marcelo Tosatti , Yair Podemsky Subject: Re: [RFC PATCH v2 16/20] rcu: Make RCU dynticks counter size configurable In-Reply-To: <20230720163056.2564824-17-vschneid@redhat.com> References: <20230720163056.2564824-1-vschneid@redhat.com> <20230720163056.2564824-17-vschneid@redhat.com> Date: Fri, 21 Jul 2023 09:17:53 +0100 Message-ID: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org 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?