linux-kernel - Re: [RFC PATCH 11/14] context-tracking: Introduce work deferral infrastructure

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Date:   Thu, 6 Jul 2023 12:01:46 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Valentin Schneider <vschneid@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, kvm@...r.kernel.org, linux-mm@...ck.org,
        bpf@...r.kernel.org, x86@...nel.org,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Christoph Hellwig <hch@...radead.org>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
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        Sami Tolvanen <samitolvanen@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Juerg Haefliger <juerg.haefliger@...onical.com>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Nadav Amit <namit@...are.com>,
        Dan Carpenter <error27@...il.com>,
        Chuang Wang <nashuiliang@...il.com>,
        Yang Jihong <yangjihong1@...wei.com>,
        Petr Mladek <pmladek@...e.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>, Song Liu <song@...nel.org>,
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        Tom Lendacky <thomas.lendacky@....com>,
        Dionna Glaze <dionnaglaze@...gle.com>,
        Thomas Weißschuh <linux@...ssschuh.net>,
        Juri Lelli <juri.lelli@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Yair Podemsky <ypodemsk@...hat.com>
Subject: Re: [RFC PATCH 11/14] context-tracking: Introduce work deferral
 infrastructure

On Thu, Jul 06, 2023 at 12:23:57AM +0200, Frederic Weisbecker wrote:
> diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
> index fdd537ea513f..ec3d172601c5 100644
> --- a/include/linux/context_tracking_state.h
> +++ b/include/linux/context_tracking_state.h
> @@ -10,14 +10,19 @@
>  #define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)
>  
>  enum ctx_state {
> +	/* Following are values */
>  	CONTEXT_DISABLED	= -1,	/* returned by ct_state() if unknown */
>  	CONTEXT_KERNEL		= 0,
>  	CONTEXT_IDLE		= 1,
>  	CONTEXT_USER		= 2,
> -	CONTEXT_GUEST		= 3,
> -	CONTEXT_MAX		= 4,
> +	/* Following are bit numbers */
> +	CONTEXT_WORK		= 2,
> +	CONTEXT_MAX		= 16,
>  };
>  
> +#define CONTEXT_MASK (BIT(CONTEXT_WORK) - 1)
> +#define CONTEXT_WORK_MASK ((BIT(CONTEXT_MAX) - 1) & ~(BIT(CONTEXT_WORK) - 1))
> +
>  /* Even value for idle, else odd. */
>  #define RCU_DYNTICKS_IDX CONTEXT_MAX

And that should be:

#define RCU_DYNTICKS_IDX BIT(CONTEXT_MAX)

Did I mention it's not even build tested? :o)