linux-kernel - Re: [PATCH 21/21] rcu/context_tracking: Merge dynticks counter and context tracking states

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Message-ID: <adf7fca9aab320abc7a0c364b3e99709e0d99548.camel@kernel.org>
Date:   Wed, 18 May 2022 17:31:32 +0200
From:   nicolas saenz julienne <nsaenz@...nel.org>
To:     Frederic Weisbecker <frederic@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Phil Auld <pauld@...hat.com>,
        Alex Belits <abelits@...vell.com>,
        Xiongfeng Wang <wangxiongfeng2@...wei.com>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yu Liao <liaoyu15@...wei.com>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Uladzislau Rezki <uladzislau.rezki@...y.com>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH 21/21] rcu/context_tracking: Merge dynticks counter and
 context tracking states

On Tue, 2022-05-03 at 12:00 +0200, Frederic Weisbecker wrote:

[...]

> diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
> index edd9f8f5b753..0841435620cf 100644
> --- a/include/linux/context_tracking_state.h
> +++ b/include/linux/context_tracking_state.h
> @@ -10,12 +10,20 @@
>  #define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)
>  
>  enum ctx_state {
> -	CONTEXT_DISABLED = -1,	/* returned by ct_state() if unknown */
> -	CONTEXT_KERNEL = 0,
> -	CONTEXT_USER,
> -	CONTEXT_GUEST,
> +	CONTEXT_DISABLED	= -1,	/* returned by ct_state() if unknown */
> +	CONTEXT_KERNEL		= 0,
> +	CONTEXT_IDLE		= 1,
> +	CONTEXT_USER		= 2,
> +	CONTEXT_GUEST		= 3,
> +	CONTEXT_MAX		= 4,
>  };
>  
> +/* Even value for idle, else odd. */
> +#define RCU_DYNTICKS_IDX CONTEXT_MAX
> +
> +#define CT_STATE_MASK (CONTEXT_MAX - 1)
> +#define CT_DYNTICKS_MASK (~CT_STATE_MASK)

Nit: These macros only work as long as we don't introduce new contexts. It's
maybe worth a comment.

Regards,

-- 
Nicolás Sáenz