linux-kernel - Re: [PATCH -rcu dev 2/3] rcu/tree: Fix issue where sometimes rcu_urgent

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Message-ID: <20190816025756.GA242309@google.com>
Date:   Thu, 15 Aug 2019 22:57:56 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     rcu@...r.kernel.org, "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        frederic@...nel.org
Subject: Re: [PATCH -rcu dev 2/3] rcu/tree: Fix issue where sometimes
 rcu_urgent_qs is not set on IPI

On Thu, Aug 15, 2019 at 10:53:10PM -0400, Joel Fernandes (Google) wrote:
> Sometimes I see rcu_urgent_qs is not set. This could be when the last
> IPI was a long time ago, however, the grace period just started. Set
> rcu_urgent_qs so the tick can indeed be stopped.
Here I meant:
                                   not be stopped.

I will resend the patch as v2.
thanks,

 - Joel


> 
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> ---
>  kernel/rcu/tree.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 322b1b57967c..856d3c9f1955 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1091,6 +1091,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
>  	if (tick_nohz_full_cpu(rdp->cpu) &&
>  		   time_after(jiffies,
>  			      READ_ONCE(rdp->last_fqs_resched) + jtsq * 3)) {
> +		WRITE_ONCE(*ruqp, true);
>  		resched_cpu(rdp->cpu);
>  		WRITE_ONCE(rdp->last_fqs_resched, jiffies);
>  	}
> -- 
> 2.23.0.rc1.153.gdeed80330f-goog
>