linux-kernel - [PATCH v3 08/21] selftests/resctrl: Ensure sibling CPU is not same as original CPU

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Date:   Tue, 20 Oct 2020 23:51:13 +0000
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     "Shuah Khan" <shuah@...nel.org>,
        "Reinette Chatre" <reinette.chatre@...el.com>,
        "Tony Luck" <tony.luck@...el.com>,
        "Babu Moger" <babu.moger@....com>,
        "James Morse" <james.morse@....com>,
        "Borislav Petkov" <bp@...en8.de>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Ravi V Shankar" <ravi.v.shankar@...el.com>
Cc:     "linux-kselftest" <linux-kselftest@...r.kernel.org>,
        "linux-kernel" <linux-kernel@...r.kernel.org>,
        Fenghua Yu <fenghua.yu@...el.com>
Subject: [PATCH v3 08/21] selftests/resctrl: Ensure sibling CPU is not same as original CPU

From: Reinette Chatre <reinette.chatre@...el.com>

The resctrl tests can accept a CPU on which the tests are run and use
default of CPU #1 if it is not provided. In the CAT test a "sibling CPU"
is determined that is from the same package where another thread will be
run.

The current algorithm with which a "sibling CPU" is determined does not
take the provided/default CPU into account and when that CPU is the
first CPU in a package then the "sibling CPU" will be selected to be the
same CPU since it starts by picking the first CPU from core_siblings_list.

Fix the "sibling CPU" selection by taking the provided/default CPU into
account and ensuring a sibling that is a different CPU is selected.

Fixes: 78941183d1b1 ("selftests/resctrl: Add Cache QoS Monitoring (CQM) selftest")
Signed-off-by: Reinette Chatre <reinette.chatre@...el.com>
Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
---
 tools/testing/selftests/resctrl/resctrlfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/resctrl/resctrlfs.c b/tools/testing/selftests/resctrl/resctrlfs.c
index 67d775d03271..05956319d9ce 100644
--- a/tools/testing/selftests/resctrl/resctrlfs.c
+++ b/tools/testing/selftests/resctrl/resctrlfs.c
@@ -268,7 +268,7 @@ int get_core_sibling(int cpu_no)
 	while (token) {
 		sibling_cpu_no = atoi(token);
 		/* Skipping core 0 as we don't want to run test on core 0 */
-		if (sibling_cpu_no != 0)
+		if (sibling_cpu_no != 0 && sibling_cpu_no != cpu_no)
 			break;
 		token = strtok(NULL, "-,");
 	}
-- 
2.29.0