linux-kernel - [PATCH v2 1/4] selftests/resctrl: Fix set up shemata with 100% allocation on first run in MBM test.

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Date:   Wed,  5 Oct 2022 10:39:30 +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
Subject: [PATCH v2 1/4] selftests/resctrl: Fix set up shemata with 100% allocation on first run in MBM test.

There is a comment "Set up shemata with 100% allocation on the first run"
in function mbm_setup(), but there is an increment bug and the condition
"num_of_runs == 0" will never be met and write_schemata() will never be
called to set schemata to 100%. This is currently fine because
resctl_val_parm->num_resctrlfs is always 1 and umount/mount will be run
in each test to set the schemata to 100%.

To make mbm_setup() future code-change proof, fix to call
write-schemata() properly when the function is called for the first time.

Also, remove static local variable 'num_of_runs' because this is not
needed as there is resctl_val_param->num_of_runs which should be used
instead like in cat_setup().

Signed-off-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
---
 tools/testing/selftests/resctrl/mbm_test.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/resctrl/mbm_test.c b/tools/testing/selftests/resctrl/mbm_test.c
index 8392e5c55ed0..4a54be314402 100644
--- a/tools/testing/selftests/resctrl/mbm_test.c
+++ b/tools/testing/selftests/resctrl/mbm_test.c
@@ -89,12 +89,11 @@ static int check_results(int span)
 static int mbm_setup(int num, ...)
 {
 	struct resctrl_val_param *p;
-	static int num_of_runs;
 	va_list param;
 	int ret = 0;

 	/* Run NUM_OF_RUNS times */
-	if (num_of_runs++ >= NUM_OF_RUNS)
+	if (p->num_of_runs >= NUM_OF_RUNS)
 		return -1;

 	va_start(param, num);
@@ -102,9 +101,10 @@ static int mbm_setup(int num, ...)
 	va_end(param);

 	/* Set up shemata with 100% allocation on the first run. */
-	if (num_of_runs == 0)
+	if (p->num_of_runs == 0)
 		ret = write_schemata(p->ctrlgrp, "100", p->cpu_no,
 				     p->resctrl_val);
+	p->num_of_runs++;

 	return ret;
 }
-- 
2.27.0