linux-kernel - Re: [PATCH] tracing: erase irqsoff trace with empty write

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Message-ID: <20170918103840.1d283502@gandalf.local.home>
Date:   Mon, 18 Sep 2017 10:38:40 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Bo Yan <byan@...dia.com>
Cc:     <mingo@...hat.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing: erase irqsoff trace with empty write

On Mon, 11 Sep 2017 11:16:35 -0700
Bo Yan <byan@...dia.com> wrote:

> One convenient way to erase trace is "echo > trace". However, this
> is currently broken if the current tracer is irqsoff tracer. This
> is because irqsoff tracer use max_buffer as the default trace
> buffer.
> 
> Set the max_buffer as the one to be cleared when it's the trace
> buffer currently in use.

Hi Bo,

I have no problems with the logic of the patch. But just one nit. The
tr->trace_buffer has been called "trace_buf" elsewhere in the file. Can
you resend with using the variable name "trace_buf" instead of "tr_buf"
just to keep it consistent in the file. It's also been called 'buf' but
trace_buf would probably be more appropriate.

Thanks!

-- Steve

> 
> Signed-off-by: Bo Yan <byan@...dia.com>
> ---
>  kernel/trace/trace.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 5360b7aec57a..1f91bdd9365b 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -4020,11 +4020,17 @@ static int tracing_open(struct inode *inode, struct file *file)
>  	/* If this file was open for write, then erase contents */
>  	if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
>  		int cpu = tracing_get_cpu(inode);
> +		struct trace_buffer *tr_buf = &tr->trace_buffer;
> +
> +#ifdef CONFIG_TRACER_MAX_TRACE
> +		if (tr->current_trace->print_max)
> +			tr_buf = &tr->max_buffer;
> +#endif
>  
>  		if (cpu == RING_BUFFER_ALL_CPUS)
> -			tracing_reset_online_cpus(&tr->trace_buffer);
> +			tracing_reset_online_cpus(tr_buf);
>  		else
> -			tracing_reset(&tr->trace_buffer, cpu);
> +			tracing_reset(tr_buf, cpu);
>  	}
>  
>  	if (file->f_mode & FMODE_READ) {