linux-kernel - Re: [PATCH v1] kernel/trace/trace: check the return value of tracing_update

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Date:   Mon, 26 Sep 2022 14:32:14 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Li Zhong <floridsleeves@...il.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com
Subject: Re: [PATCH v1] kernel/trace/trace: check the return value of
 tracing_update_buffers()

On Fri, 16 Sep 2022 19:03:53 -0700
Li Zhong <floridsleeves@...il.com> wrote:

> Check the return value of tracing_update_buffers() in case it fails.

FYI, the subject should be:

  tracing: Check the return value of tracing_update_buffers()

> 
> Signed-off-by: Li Zhong <floridsleeves@...il.com>
> ---
>  kernel/trace/trace.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index d3005279165d..0e367e326147 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -3305,7 +3305,8 @@ void trace_printk_init_buffers(void)
>  	pr_warn("**********************************************************\n");
>  
>  	/* Expand the buffers to set size */
> -	tracing_update_buffers();
> +	if (tracing_update_buffers() < 0)
> +		return;

Even if the buffers are not expanded, tracing can still work. This should
not return here. But instead we should have something like:

	/* Allocation really should not fail here at boot up or module load */
	if (tracing_update_buffers() < 0)
		pr_err("Failed to expand tracing buffers for trace_printk() calls\n");
	else
		buffers_allocate = 1;

As we still want the cmdline action done late in the code.

-- Steve


>  
>  	buffers_allocated = 1;
>