linux-kernel - [PATCH v9 3/6] selftests/resctrl: Flush stdout file buffer before executing fork()

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Date:   Thu, 13 Apr 2023 16:22:56 +0900
From:   Shaopeng Tan <tan.shaopeng@...fujitsu.com>
To:     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,
        tan.shaopeng@...fujitsu.com, Shuah Khan <skhan@...uxfoundation.org>
Subject: [PATCH v9 3/6] selftests/resctrl: Flush stdout file buffer before executing fork()

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: Shuah Khan <skhan@...uxfoundation.org>
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 08070d4fa735..38c10a8c1814 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 00864242d76c..e632657995c7 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 b31b1d9e41d1..fb00245dee92 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]);
-- 
2.27.0