linux-kernel - Re: [RFC PATCH 5/6] perf cs-etm: Improve Coresight zero timestamp warning

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Date:   Mon, 2 Aug 2021 23:17:10 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     James Clark <james.clark@....com>
Cc:     acme@...nel.org, mathieu.poirier@...aro.org,
        coresight@...ts.linaro.org, linux-perf-users@...r.kernel.org,
        suzuki.poulose@....com, mike.leach@...aro.org,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH 5/6] perf cs-etm: Improve Coresight zero timestamp
 warning

On Thu, Jul 29, 2021 at 04:58:04PM +0100, James Clark wrote:
> Only show the warning if the user hasn't already set timeless mode and
> improve the text because there was ambiguity around the meaning of '...'
> 
> Change the warning to a UI warning instead of printing straight to
> stderr because this corrupts the UI when perf report TUI is used. The UI
> warning function also handles printing to stderr when in perf script
> mode.
> 
> Suggested-by: Leo Yan <leo.yan@...aro.org>
> Signed-off-by: James Clark <james.clark@....com>

Reviewed-by: Leo Yan <leo.yan@...aro.org>

> ---
>  tools/perf/util/cs-etm-decoder/cs-etm-decoder.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> index 3e1a05bc82cc..5084bd2ca6eb 100644
> --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> @@ -324,8 +324,11 @@ cs_etm_decoder__do_hard_timestamp(struct cs_etm_queue *etmq,
>  		 * underflow.
>  		 */
>  		packet_queue->cs_timestamp = 0;
> -		WARN_ONCE(true, "Zero Coresight timestamp found at Idx:%" OCSD_TRC_IDX_STR
> -				". Decoding may be improved with --itrace=Z...\n", indx);
> +		if (!cs_etm__etmq_is_timeless(etmq))
> +			pr_warning_once("Zero Coresight timestamp found at Idx:%" OCSD_TRC_IDX_STR
> +					". Decoding may be improved by prepending 'Z' to your current --itrace arguments.\n",
> +					indx);
> +
>  	} else if (packet_queue->instr_count > elem->timestamp) {
>  		/*
>  		 * Sanity check that the elem->timestamp - packet_queue->instr_count would not
> -- 
> 2.28.0
>