linux-kernel - Re: [tip: core/rcu] rcu/tree: Mark the idle relevant functions noinstr

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Date:   Tue, 29 Sep 2020 16:52:55 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>, x86 <x86@...nel.org>
Subject: Re: [tip: core/rcu] rcu/tree: Mark the idle relevant functions
 noinstr

On Tue, Sep 29, 2020 at 10:34:54AM -0400, Steven Rostedt wrote:
> Anyway, you bring up a good point. I should have this:

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

> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 84f32dbc7be8..2d76eaaad4a7 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -6993,16 +6993,14 @@ static void ftrace_ops_assist_func(unsigned long ip, unsigned long parent_ip,
>  {
>  	int bit;
>  
> -	if ((op->flags & FTRACE_OPS_FL_RCU) && !rcu_is_watching())
> -		return;
> -
>  	bit = trace_test_and_set_recursion(TRACE_LIST_START, TRACE_LIST_MAX);
>  	if (bit < 0)
>  		return;
>  
>  	preempt_disable_notrace();
>  
> -	op->func(ip, parent_ip, op, regs);
> +	if (!(op->flags & FTRACE_OPS_FL_RCU) || rcu_is_watching())
> +		op->func(ip, parent_ip, op, regs);
>  
>  	preempt_enable_notrace();
>  	trace_clear_recursion(bit);
> 
> 
> 
> -- Steve