linux-kernel - Re: [PATCH 1/7] perf tools: Track all user changed config bits

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Message-ID: <978dd9b1-1cb0-4338-95fa-575a858cea80@linaro.org>
Date: Tue, 2 Dec 2025 10:40:49 +0000
From: James Clark <james.clark@...aro.org>
To: Leo Yan <leo.yan@....com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>,
 Suzuki K Poulose <suzuki.poulose@....com>, Mike Leach
 <mike.leach@...aro.org>, John Garry <john.g.garry@...cle.com>,
 Will Deacon <will@...nel.org>, Leo Yan <leo.yan@...ux.dev>,
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
 coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/7] perf tools: Track all user changed config bits



On 02/12/2025 10:15 am, Leo Yan wrote:
> On Mon, Dec 01, 2025 at 04:41:04PM +0000, Coresight ML wrote:
> 
> [...]
> 
>> +#define ADD_CONFIG_CHG(format_type, term_type, new_term)		\
>> +{									\
>> +	struct parse_events_term *term;					\
>> +	u64 bits = 0;							\
>> +	int type;							\
>> +									\
>> +	list_for_each_entry(term, &head_config->terms, list) {		\
>> +		if (term->type_term == PARSE_EVENTS__TERM_TYPE_USER) {  \
>> +			type = perf_pmu__format_type(pmu, term->config);\
>> +			if (type != format_type)			\
>> +				continue;				\
>> +			bits |= perf_pmu__format_bits(pmu, term->config); \
>> +		} else if (term->type_term == term_type) {		\
>> +			bits = ~(u64)0;					\
>> +		}							\
>> +	}								\
>> +									\
>> +	if (bits)							\
>> +		ADD_CONFIG_TERM_VAL(new_term, cfg_chg, bits, false);	\
>> +	return 0;							\
> 
> Nitpick: "return 0" is not needed here.  Otherwise:
> 
> Reviewed-by: Leo Yan <leo.yan@....com>

I think it's worse than not needed, it makes it stop collecting the 
changes after the first one.

It was annoying that this had to be a macro instead of a function 
because ADD_CONFIG_TERM_VAL constructs the #define name of the first 
argument.

It's probably worth putting in some effort to make ADD_CONFIG_CHG() a 
function to avoid problems like this and maybe add a test.