linux-kernel - Re: [PATCH tip/core/rcu 16/26] rcu: Mark rcu_nmi_enter() call to rcu_cleanup_after

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Date:   Tue, 23 Jun 2020 19:04:25 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     paulmck@...nel.org
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, mingo@...nel.org, jiangshanlai@...il.com,
        dipankar@...ibm.com, akpm@...ux-foundation.org,
        mathieu.desnoyers@...icios.com, josh@...htriplett.org,
        tglx@...utronix.de, rostedt@...dmis.org, dhowells@...hat.com,
        edumazet@...gle.com, fweisbec@...il.com, oleg@...hat.com,
        joel@...lfernandes.org
Subject: Re: [PATCH tip/core/rcu 16/26] rcu: Mark rcu_nmi_enter() call to
 rcu_cleanup_after_idle() noinstr

On Mon, Jun 22, 2020 at 05:21:37PM -0700, paulmck@...nel.org wrote:
> From: "Paul E. McKenney" <paulmck@...nel.org>
> 
> The objtool complains about the call to rcu_cleanup_after_idle() from
> rcu_nmi_enter(), so this commit adds instrumentation_begin() before that
> call and instrumentation_end() after it.

Hmm, I've not seen this one. Still,

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

> Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> ---
>  kernel/rcu/tree.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 08e3648..67912ad 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -980,8 +980,11 @@ noinstr void rcu_nmi_enter(void)
>  		rcu_dynticks_eqs_exit();
>  		// ... but is watching here.
>  
> -		if (!in_nmi())
> +		if (!in_nmi()) {
> +			instrumentation_begin();
>  			rcu_cleanup_after_idle();
> +			instrumentation_end();
> +		}
>  
>  		incby = 1;
>  	} else if (!in_nmi()) {
> -- 
> 2.9.5
>