linux-kernel - Re: [RESEND PATCH v12 1/3] perf tool: arm: Refactor event list iteration in auxtrace_record_

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Date:   Thu, 15 Sep 2022 11:57:41 +0800
From:   Yicong Yang <yangyicong@...wei.com>
To:     John Garry <john.garry@...wei.com>, Leo Yan <leo.yan@...aro.org>
CC:     <yangyicong@...ilicon.com>, <acme@...nel.org>,
        <peterz@...radead.org>, <alexander.shishkin@...ux.intel.com>,
        <james.clark@....com>, <will@...nel.org>,
        <mathieu.poirier@...aro.org>, <mark.rutland@....com>,
        <suzuki.poulose@....com>, <jonathan.cameron@...wei.com>,
        <mike.leach@...aro.org>, <gregkh@...uxfoundation.org>,
        <helgaas@...nel.org>, <lorenzo.pieralisi@....com>,
        <shameerali.kolothum.thodi@...wei.com>, <mingo@...hat.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-pci@...r.kernel.org>, <linux-perf-users@...r.kernel.org>,
        <prime.zeng@...wei.com>, <zhangshaokun@...ilicon.com>,
        <linuxarm@...wei.com>, <liuqi6124@...il.com>
Subject: Re: [RESEND PATCH v12 1/3] perf tool: arm: Refactor event list
 iteration in auxtrace_record__init()

On 2022/9/14 22:27, Leo Yan wrote:
> On Wed, Sep 14, 2022 at 02:47:43PM +0100, John Garry wrote:
> 
> [...]
> 
>>>   struct auxtrace_record
>>>   *auxtrace_record__init(struct evlist *evlist, int *err)
>>>   {
>>> -	struct perf_pmu	*cs_etm_pmu;
>>> +	struct perf_pmu	*cs_etm_pmu = NULL;
>>> +	struct perf_pmu **arm_spe_pmus = NULL;
>>>   	struct evsel *evsel;
>>> -	bool found_etm = false;
>>> +	struct perf_pmu *found_etm = NULL;
>>>   	struct perf_pmu *found_spe = NULL;
>>> -	struct perf_pmu **arm_spe_pmus = NULL;
>>> +	int auxtrace_event_cnt = 0;
>>>   	int nr_spes = 0;
>>> -	int i = 0;
>>>   	if (!evlist)
>>>   		return NULL;
>>> @@ -68,24 +84,23 @@ struct auxtrace_record
>>>   	arm_spe_pmus = find_all_arm_spe_pmus(&nr_spes, err);
>>>   	evlist__for_each_entry(evlist, evsel) {
>>> -		if (cs_etm_pmu &&
>>> -		    evsel->core.attr.type == cs_etm_pmu->type)
>>> -			found_etm = true;
>>> -
>>> -		if (!nr_spes || found_spe)
>>> -			continue;
>>> -
>>> -		for (i = 0; i < nr_spes; i++) {
>>> -			if (evsel->core.attr.type == arm_spe_pmus[i]->type) {
>>> -				found_spe = arm_spe_pmus[i];
>>> -				break;
>>> -			}
>>> -		}
>>> +		if (cs_etm_pmu && !found_etm) +			found_etm =
>>> find_pmu_for_event(&cs_etm_pmu, 1, evsel);
>>> +
>>> +		if (arm_spe_pmus && !found_spe)
>>> +			found_spe = find_pmu_for_event(arm_spe_pmus, nr_spes, evsel);
>>
>> should you break if found_etm and found_spe are set? Or, indeed, error and
>> return directly as we do below? Indeed, I am not sure why you even require
>> auxtrace_event_cnt
> 
> I think this was my suggestion :)
> 

yes. thanks :). It's dicussed in v7 and for more information:
https://lore.kernel.org/lkml/20220430073411.GA657977@leoy-ThinkPad-X240s/

> We can check if both 'found_etm' and 'found_spe' are set and directly
> break (and bail out) for this case.  But it would introduce more complex
> checking if we connect with patch 2 with new flag 'found_ptt', something
> like:
> 
>   if ((found_etm && found_spe) ||
>       (found_etm && found_ptt) ||
>       (found_spe && found_ptt))
>       break;
> 
> This is hard for later's extension if we need to support a new auxtrace
> event, so using auxtrace_event_cnt would be easier to extend more
> auxtrace event on Arm platforms.
> 
> Thanks,
> Leo
> 
>>>   	}
>>> +
>>>   	free(arm_spe_pmus);
>>> -	if (found_etm && found_spe) {
>>> -		pr_err("Concurrent ARM Coresight ETM and SPE operation not currently supported\n");
>>> +	if (found_etm)
>>> +		auxtrace_event_cnt++;
>>> +
>>> +	if (found_spe)
>>> +		auxtrace_event_cnt++;
>>> +
>>> +	if (auxtrace_event_cnt > 1) {
>>> +		pr_err("Concurrent AUX trace operation not currently supported\n");
>>>   		*err = -EOPNOTSUPP;
>>>   		return NULL;
>>>   	}
>>
> .
>