linux-kernel - Re: [PATCH v2] perf test tsc: Fix error message report when not supported.

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Date:   Thu, 7 Apr 2022 09:59:09 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Chengdong Li <brytonlee01@...il.com>, adrian.hunter@...el.com,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, namhyung@...nel.org
Cc:     ak@...ux.intel.com, likexu@...cent.com, chengdongli@...cent.com
Subject: Re: [PATCH v2] perf test tsc: Fix error message report when not
 supported.

On 06/04/2022 13.06, Chengdong Li wrote:
> By default `perf test tsc` does not return the error message
> when child process detected kernel does not support. Instead, child
> process print error message to stderr, unfortunately the stderr is
> redirected to /dev/null when verbose <= 0.
> 
> This patch did three things:
> - returns TEST_SKIP to parent process instead of TEST_OK when
>   perf_read_tsc_conversion() is not supported.
> - add a new subtest of testing if TSC is supported on current
>   architecture by moving exist code to a separate function.
> - extended test suite definition to contain above two subtests.
> 
> Changes since v1 (thanks for the feedback from Adrian Hunter):
> - rebase commit to current source.
> 
> Signed-off-by: Chengdong Li <chengdongli@...cent.com>
> ---
>  tools/perf/tests/perf-time-to-tsc.c | 36 +++++++++++++++++++++--------
>  1 file changed, 27 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/perf/tests/perf-time-to-tsc.c b/tools/perf/tests/perf-time-to-tsc.c
> index d12d0ad81801..fc7c380af5a0 100644
> --- a/tools/perf/tests/perf-time-to-tsc.c
> +++ b/tools/perf/tests/perf-time-to-tsc.c
> @@ -47,6 +47,17 @@
>  	}					\
>  }
>  
> +static int test__tsc_is_supported(struct test_suite *test __maybe_unused,
> +				  int subtest __maybe_unused)
> +{
> +	if (!TSC_IS_SUPPORTED) {
> +		pr_debug("Test not supported on this architecture");

Message better ending with "\n" I think

> +		return TEST_SKIP;
> +	}
> +
> +	return TEST_OK;
> +}
> +
>  /**
>   * test__perf_time_to_tsc - test converting perf time to TSC.
>   *
> @@ -70,7 +81,7 @@ static int test__perf_time_to_tsc(struct test_suite *test __maybe_unused, int su
>  	struct perf_cpu_map *cpus = NULL;
>  	struct evlist *evlist = NULL;
>  	struct evsel *evsel = NULL;
> -	int err = -1, ret, i;
> +	int err = TEST_FAIL, ret, i;
>  	const char *comm1, *comm2;
>  	struct perf_tsc_conversion tc;
>  	struct perf_event_mmap_page *pc;
> @@ -79,10 +90,6 @@ static int test__perf_time_to_tsc(struct test_suite *test __maybe_unused, int su
>  	u64 test_time, comm1_time = 0, comm2_time = 0;
>  	struct mmap *md;
>  
> -	if (!TSC_IS_SUPPORTED) {
> -		pr_debug("Test not supported on this architecture");
> -		return TEST_SKIP;
> -	}
>  
>  	threads = thread_map__new(-1, getpid(), UINT_MAX);
>  	CHECK_NOT_NULL__(threads);
> @@ -124,8 +131,8 @@ static int test__perf_time_to_tsc(struct test_suite *test __maybe_unused, int su
>  	ret = perf_read_tsc_conversion(pc, &tc);
>  	if (ret) {
>  		if (ret == -EOPNOTSUPP) {
> -			fprintf(stderr, " (not supported)");
> -			return 0;
> +			pr_debug("perf_read_tsc_conversion is not supported in current kernel");
> +			err = TEST_SKIP;
>  		}
>  		goto out_err;
>  	}
> @@ -191,7 +198,7 @@ static int test__perf_time_to_tsc(struct test_suite *test __maybe_unused, int su
>  	    test_tsc >= comm2_tsc)
>  		goto out_err;
>  
> -	err = 0;
> +	err = TEST_OK;
>  
>  out_err:
>  	evlist__delete(evlist);
> @@ -200,4 +207,15 @@ static int test__perf_time_to_tsc(struct test_suite *test __maybe_unused, int su
>  	return err;
>  }
>  
> -DEFINE_SUITE("Convert perf time to TSC", perf_time_to_tsc);
> +static struct test_case time_to_tsc_tests[] = {
> +	TEST_CASE_REASON("TSC support", tsc_is_supported,
> +			 "This architecture does not support"),

The 2nd test case runs anyway, so I am not sure another
test case is needed?

> +	TEST_CASE_REASON("Perf time to TSC", perf_time_to_tsc,
> +			 "perf_read_tsc_conversion is not supported"),
> +	{ .name = NULL, }
> +};
> +
> +struct test_suite suite__perf_time_to_tsc = {
> +	.desc = "Convert perf time to TSC",
> +	.test_cases = time_to_tsc_tests,
> +};