linux-kernel - Re: [PATCH 01/10] rcu: Use rcu_segcblist_segempty() instead of open coding it

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Date:   Mon, 2 Oct 2023 08:38:11 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, rcu <rcu@...r.kernel.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Qiuxu Zhuo <qiuxu.zhuo@...el.com>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH 01/10] rcu: Use rcu_segcblist_segempty() instead of open
 coding it

On Fri, Sep 08, 2023 at 10:35:54PM +0200, Frederic Weisbecker wrote:
> This makes the code more readable.
> 
> Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
> Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> Signed-off-by: Frederic Weisbecker <frederic@...nel.org>

Reviewed-by: Paul E. McKenney <paulmck@...nel.org>

> ---
>  kernel/rcu/rcu_segcblist.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c
> index f71fac422c8f..1693ea22ef1b 100644
> --- a/kernel/rcu/rcu_segcblist.c
> +++ b/kernel/rcu/rcu_segcblist.c
> @@ -368,7 +368,7 @@ bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
>  	smp_mb(); /* Ensure counts are updated before callback is entrained. */
>  	rhp->next = NULL;
>  	for (i = RCU_NEXT_TAIL; i > RCU_DONE_TAIL; i--)
> -		if (rsclp->tails[i] != rsclp->tails[i - 1])
> +		if (!rcu_segcblist_segempty(rsclp, i))
>  			break;
>  	rcu_segcblist_inc_seglen(rsclp, i);
>  	WRITE_ONCE(*rsclp->tails[i], rhp);
> @@ -551,7 +551,7 @@ bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq)
>  	 * as their ->gp_seq[] grace-period completion sequence number.
>  	 */
>  	for (i = RCU_NEXT_READY_TAIL; i > RCU_DONE_TAIL; i--)
> -		if (rsclp->tails[i] != rsclp->tails[i - 1] &&
> +		if (!rcu_segcblist_segempty(rsclp, i) &&
>  		    ULONG_CMP_LT(rsclp->gp_seq[i], seq))
>  			break;
>  
> -- 
> 2.41.0
>