linux-kernel - Re: [PATCH v3 3/5] selftests/resctrl: Flush stdout file buffer before executing fork()

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Date:   Wed, 2 Nov 2022 03:29:09 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Shaopeng Tan <tan.shaopeng@...fujitsu.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Shuah Khan <shuah@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v3 3/5] selftests/resctrl: Flush stdout file buffer before
 executing fork()

On 11/1/22 03:43, Shaopeng Tan wrote:
> When a process has buffered output, a child process created by fork()
> will also copy buffered output. When using kselftest framework,
> the output (resctrl test result message) will be printed multiple times.
> 
> Add fflush() to flush out the buffered output before executing fork().
> 
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> Signed-off-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> ---
>   tools/testing/selftests/resctrl/cat_test.c    | 1 +
>   tools/testing/selftests/resctrl/resctrl_val.c | 1 +
>   tools/testing/selftests/resctrl/resctrlfs.c   | 1 +
>   3 files changed, 3 insertions(+)
> 
> diff --git a/tools/testing/selftests/resctrl/cat_test.c b/tools/testing/selftests/resctrl/cat_test.c
> index 1c5e90c63254..6a8306b0a109 100644
> --- a/tools/testing/selftests/resctrl/cat_test.c
> +++ b/tools/testing/selftests/resctrl/cat_test.c
> @@ -167,6 +167,7 @@ int cat_perf_miss_val(int cpu_no, int n, char *cache_type)
>   		return errno;
>   	}
>   
> +	fflush(stdout);
>   	bm_pid = fork();
>   
>   	/* Set param values for child thread which will be allocated bitmask
> diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
> index b32b96356ec7..6948843bf995 100644
> --- a/tools/testing/selftests/resctrl/resctrl_val.c
> +++ b/tools/testing/selftests/resctrl/resctrl_val.c
> @@ -629,6 +629,7 @@ int resctrl_val(char **benchmark_cmd, struct resctrl_val_param *param)
>   	 * Fork to start benchmark, save child's pid so that it can be killed
>   	 * when needed
>   	 */
> +	fflush(stdout);
>   	bm_pid = fork();
>   	if (bm_pid == -1) {
>   		perror("# Unable to fork");
> diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
> index 8546bc9f1786..d95688298469 100644
> --- a/tools/testing/selftests/resctrl/resctrlfs.c
> +++ b/tools/testing/selftests/resctrl/resctrlfs.c
> @@ -678,6 +678,7 @@ int filter_dmesg(void)
>   		perror("pipe");
>   		return ret;
>   	}
> +	fflush(stdout);
>   	pid = fork();
>   	if (pid == 0) {
>   		close(pipefds[0]);

Good find. Looks good to me.

Reviewed-by: Shuah Khan <skhan@...uxfoundation.org>

thanks,
-- Shuah