linux-kernel - [PATCH] selftests/livepatch: Do not check order when using "comm" for dmesg checking

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Date:   Thu, 27 Aug 2020 13:07:09 +0200
From:   Miroslav Benes <mbenes@...e.cz>
To:     jpoimboe@...hat.com, jikos@...nel.org, pmladek@...e.com,
        joe.lawrence@...hat.com, shuah@...nel.org
Cc:     live-patching@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, Miroslav Benes <mbenes@...e.cz>
Subject: [PATCH] selftests/livepatch: Do not check order when using "comm" for dmesg checking

check_result() uses "comm" to check expected results of selftests output
in dmesg. Everything works fine if timestamps in dmesg are unique. If
not, like in this example

[   86.844422] test_klp_callbacks_demo: pre_unpatch_callback: test_klp_callbacks_mod -> [MODULE_STATE_LIVE] Normal state
[   86.844422] livepatch: 'test_klp_callbacks_demo': starting unpatching transition

, "comm" fails with "comm: file 2 is not in sorted order". Suppress the
order checking with --nocheck-order option.

Signed-off-by: Miroslav Benes <mbenes@...e.cz>
---

The strange thing is, I can reproduce the issue easily and reliably on
older codestreams (4.12) but not on current upstream in my testing
environment. I think the change makes sense regardless though.

 tools/testing/selftests/livepatch/functions.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/livepatch/functions.sh b/tools/testing/selftests/livepatch/functions.sh
index 1aba83c87ad3..846c7ed71556 100644
--- a/tools/testing/selftests/livepatch/functions.sh
+++ b/tools/testing/selftests/livepatch/functions.sh
@@ -278,7 +278,7 @@ function check_result {
 	# help differentiate repeated testing runs.  Remove them with a
 	# post-comparison sed filter.
 
-	result=$(dmesg | comm -13 "$SAVED_DMESG" - | \
+	result=$(dmesg | comm --nocheck-order -13 "$SAVED_DMESG" - | \
 		 grep -e 'livepatch:' -e 'test_klp' | \
 		 grep -v '\(tainting\|taints\) kernel' | \
 		 sed 's/^\[[ 0-9.]*\] //')
-- 
2.28.0