linux-kernel - Re: [PATCH v2] ring-buffer: Add offset of events in dump on mismatch

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Message-Id: <20231208200738.8931aef2857866baf469505a@kernel.org>
Date:   Fri, 8 Dec 2023 20:07:38 +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>,
        Mark Rutland <mark.rutland@....com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH v2] ring-buffer: Add offset of events in dump on
 mismatch

On Thu, 7 Dec 2023 17:31:08 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
> 
> On bugs that have the ring buffer timestamp get out of sync, the config
> CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS, that checks for it and if it is
> detected it causes a dump of the bad sub buffer.
> 
> It shows each event and their timestamp as well as the delta in the event.
> But it's also good to see the offset into the subbuffer for that event to
> know if how close to the end it is.
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>

Looks good to me.

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

Thanks!

> ---
> Changes since v1: https://lore.kernel.org/linux-trace-kernel/20231207171613.0592087d@gandalf.local.home
> 
> - Add "0x" before the "%x" to make the print less confusing (Mathieu Desnoyers)
> 
>  kernel/trace/ring_buffer.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 8d2a4f00eca9..09d4b1aa8820 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -3424,23 +3424,27 @@ static void dump_buffer_page(struct buffer_data_page *bpage,
>  		case RINGBUF_TYPE_TIME_EXTEND:
>  			delta = rb_event_time_stamp(event);
>  			ts += delta;
> -			pr_warn("  [%lld] delta:%lld TIME EXTEND\n", ts, delta);
> +			pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n",
> +				e, ts, delta);
>  			break;
>  
>  		case RINGBUF_TYPE_TIME_STAMP:
>  			delta = rb_event_time_stamp(event);
>  			ts = rb_fix_abs_ts(delta, ts);
> -			pr_warn("  [%lld] absolute:%lld TIME STAMP\n", ts, delta);
> +			pr_warn(" 0x%x:  [%lld] absolute:%lld TIME STAMP\n",
> +				e, ts, delta);
>  			break;
>  
>  		case RINGBUF_TYPE_PADDING:
>  			ts += event->time_delta;
> -			pr_warn("  [%lld] delta:%d PADDING\n", ts, event->time_delta);
> +			pr_warn(" 0x%x:  [%lld] delta:%d PADDING\n",
> +				e, ts, event->time_delta);
>  			break;
>  
>  		case RINGBUF_TYPE_DATA:
>  			ts += event->time_delta;
> -			pr_warn("  [%lld] delta:%d\n", ts, event->time_delta);
> +			pr_warn(" 0x%x:  [%lld] delta:%d\n",
> +				e, ts, event->time_delta);
>  			break;
>  
>  		default:
> -- 
> 2.42.0
> 


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