linux-kernel - Re: [PATCH RFC 3/8] rcu: Add back the cpuend tracepoint

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Message-Id: <20180514181227.GE26088@linux.vnet.ibm.com>
Date:   Mon, 14 May 2018 11:12:27 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>, byungchul.park@....com,
        kernel-team@...roid.com
Subject: Re: [PATCH RFC 3/8] rcu: Add back the cpuend tracepoint

On Sun, May 13, 2018 at 08:15:36PM -0700, Joel Fernandes (Google) wrote:
> Commit be4b8beed87d ("rcu: Move RCU's grace-period-change code to ->gp_seq")
> removed the cpuend grace period trace point. This patch adds it back.
> 
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>

Good catch!!!  I queued this to be squashed into the offending commit,
with attribution.

							Thanx, Paul

> ---
>  kernel/rcu/tree.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 9ad931bff409..29ccc60bdbfc 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1774,10 +1774,12 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp,
> 
>  	/* Handle the ends of any preceding grace periods first. */
>  	if (rcu_seq_completed_gp(rdp->gp_seq, rnp->gp_seq) ||
> -	    unlikely(READ_ONCE(rdp->gpwrap)))
> +	    unlikely(READ_ONCE(rdp->gpwrap))) {
>  		ret = rcu_advance_cbs(rsp, rnp, rdp); /* Advance callbacks. */
> -	else
> +		trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("cpuend"));
> +	} else {
>  		ret = rcu_accelerate_cbs(rsp, rnp, rdp); /* Recent callbacks. */
> +	}
> 
>  	/* Now handle the beginnings of any new-to-this-CPU grace periods. */
>  	if (rcu_seq_new_gp(rdp->gp_seq, rnp->gp_seq) ||
> -- 
> 2.17.0.441.gb46fe60e1d-goog
>