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Message-ID: <d600f5c4-290b-d575-19a0-9cc83f77caaa@alu.unizg.hr>
Date:   Fri, 6 Jan 2023 22:18:03 +0100
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Subject: BUG: assert spuriously fails in selftest/proc/proc-uptime-001.c
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To:     Alexey Dobriyan <adobriyan@gmail.com>
Cc:     linux-kselftest@vger.kernel.org, Shuah Khan <shuah@kernel.org>,
        Brian Foster <bfoster@redhat.com>,
        Guo Zhengkui <guozhengkui@vivo.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Thorsten Leemhuis <regressions@leemhuis.info>,
        Andrew Morton <akpm@linux-foundation.org>
References: <fd9206f6-3ec4-cafc-e313-dfddf957bd5e@alu.unizg.hr>
 <Y7h2xvzKLg36DSq8@p183>
From:   Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
In-Reply-To: <Y7h2xvzKLg36DSq8@p183>
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Hi all,

In the same environment as the previous bug report (Lenovo Ideapad 3 15ITL6 laptop
running Ubuntu 22.10 kinetic kudu and 6.2-rc2 vanilla Torvalds tree kernel), the
next test in the ...selftest/proc/* sequence spuriously fails in assert (i1 <= i0).

Please note that the compiler is the novelty GCC 12.2.0-3ubuntu1.

This was previously hidden by premature hang in the `make kselftest` run due to
proc-empty-vm an proc-pid-vm problems that are now fixed.

root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
proc-uptime-001: proc-uptime-001.c:39: main: Assertion `i1 >= i0' failed.
Aborted (core dumped)
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
proc-uptime-001: proc-uptime-001.c:39: main: Assertion `i1 >= i0' failed.
Aborted (core dumped)
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
proc-uptime-001: proc-uptime-001.c:39: main: Assertion `i1 >= i0' failed.
Aborted (core dumped)
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
proc-uptime-001: proc-uptime-001.c:39: main: Assertion `i1 >= i0' failed.
Aborted (core dumped)
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
proc-uptime-001: proc-uptime-001.c:39: main: Assertion `i1 >= i0' failed.
Aborted (core dumped)
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
proc-uptime-001: proc-uptime-001.c:39: main: Assertion `i1 >= i0' failed.
Aborted (core dumped)
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
proc-uptime-001: proc-uptime-001.c:39: main: Assertion `i1 >= i0' failed.
Aborted (core dumped)
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
proc-uptime-001: proc-uptime-001.c:39: main: Assertion `i1 >= i0' failed.
Aborted (core dumped)
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
proc-uptime-001: proc-uptime-001.c:39: main: Assertion `i1 >= i0' failed.
Aborted (core dumped)
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
proc-uptime-001: proc-uptime-001.c:39: main: Assertion `i1 >= i0' failed.
Aborted (core dumped)
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001
proc-uptime-001: proc-uptime-001.c:39: main: Assertion `i1 >= i0' failed.
Aborted (core dumped)
root@marvin-IdeaPad-3-15ITL6:/home/marvin/linux/kernel/linux_torvalds/tools/testing/selftests/proc# ./proc-uptime-001

It happens about half of the times the program is called.

The source seems OK, I can't tell why the idle counter doesn't look monotonic to
the program.

Hope this helps.

BTW, good news: this time I have checked independently, and this is the last test from the .../selftest/proc
group that doesn't have clean exit code 0.

Thanks,
Mirsad

--
Mirsad Goran Todorovac
Sistem inženjer
Grafički fakultet | Akademija likovnih umjetnosti
Sveučilište u Zagrebu
-- 
System engineer
Faculty of Graphic Arts | Academy of Fine Arts
University of Zagreb, Republic of Croatia
The European Union