linux-kernel - Re: [PATCH] ring-buffer: Remove jump to out label in ring_buffer_swap

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Message-Id: <20250528093217.5a106d3561b2234080e3be35@kernel.org>
Date: Wed, 28 May 2025 09:32:17 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH] ring-buffer: Remove jump to out label in
 ring_buffer_swap_cpu()

On Tue, 27 May 2025 14:57:53 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: Steven Rostedt <rostedt@...dmis.org>
> 
> The function ring_buffer_swap_cpu() has a bunch of jumps to the label out
> that simply returns "ret". There's no reason to jump to a label that
> simply returns a value. Just return directly from there.
> 
> This goes back to almost the beginning when commit 8aabee573dff
> ("ring-buffer: remove unneeded get_online_cpus") was introduced. That
> commit removed a put_online_cpus() from that label, but never updated all
> the jumps to it that now no longer needed to do anything but return a
> value.
> 

Looks good to me.

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> ---
>  kernel/trace/ring_buffer.c | 23 +++++++++--------------
>  1 file changed, 9 insertions(+), 14 deletions(-)
> 
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 897ce51d3bbf..e2aa90dc8d9e 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -6309,37 +6309,33 @@ int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
>  
>  	if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
>  	    !cpumask_test_cpu(cpu, buffer_b->cpumask))
> -		goto out;
> +		return -EINVAL;
>  
>  	cpu_buffer_a = buffer_a->buffers[cpu];
>  	cpu_buffer_b = buffer_b->buffers[cpu];
>  
>  	/* It's up to the callers to not try to swap mapped buffers */
> -	if (WARN_ON_ONCE(cpu_buffer_a->mapped || cpu_buffer_b->mapped)) {
> -		ret = -EBUSY;
> -		goto out;
> -	}
> +	if (WARN_ON_ONCE(cpu_buffer_a->mapped || cpu_buffer_b->mapped))
> +		return -EBUSY;
>  
>  	/* At least make sure the two buffers are somewhat the same */
>  	if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
> -		goto out;
> +		return -EINVAL;
>  
>  	if (buffer_a->subbuf_order != buffer_b->subbuf_order)
> -		goto out;
> -
> -	ret = -EAGAIN;
> +		return -EINVAL;
>  
>  	if (atomic_read(&buffer_a->record_disabled))
> -		goto out;
> +		return -EAGAIN;
>  
>  	if (atomic_read(&buffer_b->record_disabled))
> -		goto out;
> +		return -EAGAIN;
>  
>  	if (atomic_read(&cpu_buffer_a->record_disabled))
> -		goto out;
> +		return -EAGAIN;
>  
>  	if (atomic_read(&cpu_buffer_b->record_disabled))
> -		goto out;
> +		return -EAGAIN;
>  
>  	/*
>  	 * We can't do a synchronize_rcu here because this
> @@ -6376,7 +6372,6 @@ int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
>  out_dec:
>  	atomic_dec(&cpu_buffer_a->record_disabled);
>  	atomic_dec(&cpu_buffer_b->record_disabled);
> -out:
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
> -- 
> 2.47.2
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>