linux-kernel - Re: [PATCH v1] perf test workload: Add thread count argument to thloop

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Message-ID: <aQDcWtHI9LSBAWw9@x1>
Date: Tue, 28 Oct 2025 12:08:10 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] perf test workload: Add thread count argument to
 thloop

On Mon, Oct 27, 2025 at 01:14:05PM -0700, Ian Rogers wrote:
> Allow the number of threads for the thloop workload to be increased
> beyond the normal 2. Add error checking to the parsed time and thread
> count values.
> 
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> ---
>  tools/perf/tests/workloads/thloop.c | 41 ++++++++++++++++++++++++-----
>  1 file changed, 35 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/tests/workloads/thloop.c b/tools/perf/tests/workloads/thloop.c
> index 457b29f91c3e..dbb88bcf49e0 100644
> --- a/tools/perf/tests/workloads/thloop.c
> +++ b/tools/perf/tests/workloads/thloop.c
> @@ -31,21 +31,50 @@ static void *thfunc(void *arg)
>  
>  static int thloop(int argc, const char **argv)
>  {
> -	int sec = 1;
> -	pthread_t th;
> +	int nt = 2, sec = 1, err = 1;
> +	pthread_t *thread_list = NULL;
>  
>  	if (argc > 0)
>  		sec = atoi(argv[0]);
>  
> +	if (sec <= 0) {
> +		fprintf(stderr, "Error: seconds (%d) must be >= 1\n", sec);
> +		return 1;
> +	}
> +
> +	if (argc > 1)
> +		nt = atoi(argv[1]);
> +
> +	if (nt <= 0) {
> +		fprintf(stderr, "Error: thread count (%d) must be >= 1\n", nt);
> +		return 1;
> +	}
> +
>  	signal(SIGINT, sighandler);
>  	signal(SIGALRM, sighandler);
> -	alarm(sec);
>  
> -	pthread_create(&th, NULL, thfunc, test_loop);
> +	thread_list = calloc(nt, sizeof(pthread_t));
> +	if (thread_list == NULL) {
> +		fprintf(stderr, "Error: malloc failed for %d threads\n", nt);
> +		goto out;
> +	}
> +	for (int i = 1; i < nt; i++) {
> +		int ret = pthread_create(&thread_list[i], NULL, thfunc, test_loop);
> +
> +		if (ret) {
> +			fprintf(stderr, "Error: failed to create thread %d\n", i);

With nt=2 what happens if you manage to create the first thread but not
the second? The first would not have its pthread_join()?

> +			goto out;
> +		}
> +	}
> +	alarm(sec);
>  	test_loop();
> -	pthread_join(th, NULL);
> +	for (int i = 1; i < nt; i++)
> +		pthread_join(thread_list[i], /*retval=*/NULL);
>  
> -	return 0;
> +	err = 0;
> +out:
> +	free(thread_list);
> +	return err;
>  }
>  
>  DEFINE_WORKLOAD(thloop);
> -- 
> 2.51.1.851.g4ebd6896fd-goog