linux-kernel - Re: [PATCH v2 2/5] perf pmu: Support more complex PMU event aliasing

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Date:   Mon, 17 Jun 2019 10:06:08 +0100
From:   John Garry <john.garry@...wei.com>
To:     Jiri Olsa <jolsa@...hat.com>
CC:     <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
        <alexander.shishkin@...ux.intel.com>, <namhyung@...nel.org>,
        <tmricht@...ux.ibm.com>, <brueckner@...ux.ibm.com>,
        <kan.liang@...ux.intel.com>, <ben@...adent.org.uk>,
        <mathieu.poirier@...aro.org>, <mark.rutland@....com>,
        <will.deacon@....com>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...wei.com>, <linux-arm-kernel@...ts.infradead.org>,
        <zhangshaokun@...ilicon.com>
Subject: Re: [PATCH v2 2/5] perf pmu: Support more complex PMU event aliasing

On 16/06/2019 10:58, Jiri Olsa wrote:
> On Fri, Jun 14, 2019 at 10:08:00PM +0800, John Garry wrote:
>> The jevent "Unit" field is used for uncore PMU alias definition.
>>
>> The form uncore_pmu_example_X is supported, where "X" is a wildcard,
>> to support multiple instances of the same PMU in a system.
>>
>> Unfortunately this format not suitable for all uncore PMUs; take the Hisi
>> DDRC uncore PMU for example, where the name is in the form
>> hisi_scclX_ddrcY.
>>
>> For the current jevent parsing, we would be required to hardcode an uncore
>> alias translation for each possible value of X. This is not scalable.
>>
>> Instead, add support for "Unit" field in the form "hisi_sccl,ddrc", where
>> we can match by hisi_scclX and ddrcY. Tokens in Unit field are
>> delimited by ','.
>>
>> Signed-off-by: John Garry <john.garry@...wei.com>
>> ---
>>  tools/perf/util/pmu.c | 39 ++++++++++++++++++++++++++++++++++-----
>>  1 file changed, 34 insertions(+), 5 deletions(-)
>>
>> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
>> index 7e7299fee550..bc71c60589b5 100644
>> --- a/tools/perf/util/pmu.c
>> +++ b/tools/perf/util/pmu.c
>> @@ -700,6 +700,39 @@ struct pmu_events_map *perf_pmu__find_map(struct perf_pmu *pmu)
>>  	return map;
>>  }
>>
>> +static bool pmu_uncore_alias_match(const char *pmu_name, const char *name)
>> +{
>> +	char *tmp, *tok, *str;
>> +	bool res;
>> +
>> +	str = strdup(pmu_name);
>> +	if (!str)
>> +		return false;
>> +
>> +	/*
>> +	 * uncore alias may be from different PMU with common
>> +	 * prefix or matching tokens.
>> +	 */
>> +	tok = strtok_r(str, ",", &tmp);
>> +	if (strncmp(pmu_name, tok, strlen(tok))) {
>

Hi Jirka,

> if tok is NULL in here we crash
>

As I see, tok could not be NULL. If str contains no delimiters, then we 
just return same as str in tok.

Can you see tok being NULL?

>> +		res = false;
>> +		goto out;
>> +	}
>> +
>> +	for (; tok; name += strlen(tok), tok = strtok_r(NULL, ",", &tmp)) {
>
> why is name shifted in here?

I want to ensure that we match the tokens in order and also guard 
against possible repeated token matches in 'name'.

Thanks,
John

>
> jirka
>
>> +		name = strstr(name, tok);
>> +		if (!name) {
>> +			res = false;
>> +			goto out;
>> +		}
>> +	}
>> +
>> +	res = true;
>> +out:
>> +	free(str);
>> +	return res;
>> +}
>> +
>>  /*
>>   * From the pmu_events_map, find the table of PMU events that corresponds
>>   * to the current running CPU. Then, add all PMU events from that table
>> @@ -730,12 +763,8 @@ static void pmu_add_cpu_aliases(struct list_head *head, struct perf_pmu *pmu)
>>  			break;
>>  		}
>>
>> -		/*
>> -		 * uncore alias may be from different PMU
>> -		 * with common prefix
>> -		 */
>>  		if (pmu_is_uncore(name) &&
>> -		    !strncmp(pname, name, strlen(pname)))
>> +		    pmu_uncore_alias_match(pname, name))
>>  			goto new_alias;
>>
>>  		if (strcmp(pname, name))
>> --
>> 2.17.1
>>
>
> .
>