linux-kernel - Re: [PATCH 1/2] of: unittest: option to allow tests that trigger kernel stack dump

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Date:   Tue, 28 Feb 2023 20:07:15 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Frank Rowand <frowand.list@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Jonathan Corbet <corbet@....net>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org
Subject: Re: [PATCH 1/2] of: unittest: option to allow tests that trigger
 kernel stack dump

On 2/28/23 17:21, Frank Rowand wrote:
> Commit 74df14cd301a ("of: unittest: add node lifecycle tests") added
> some tests that trigger a kernel stack dump.  Filtering the boot
> messages with scripts/dtc/of_unittest_expect detects that the stack
> dump is expected instead of being a test error.
> 
> Test beds might interpret the stack dumps as errors, resulting in
> needless debugging and error reports.  These test beds are likely
> to remove unittests due to these stack dumps. To avoid these problems,
> have unittest default to skip the tests that trigger a stack dump.
> 
> Add a kernel cmdline option to not skip those tests.  This option can
> be used by testers who are able to interpret the stack dumps as not
> an error.
> 
> Signed-off-by: Frank Rowand <frowand.list@...il.com>
> ---
>   drivers/of/unittest.c | 54 ++++++++++++++++++++++++++++++++++++++++---
>   1 file changed, 51 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c
> index b5a7a31d8bd2..3a9bc2bc4ba1 100644
> --- a/drivers/of/unittest.c
> +++ b/drivers/of/unittest.c
> @@ -70,6 +70,36 @@ static struct unittest_results {
>   #define EXPECT_NOT_END(level, fmt, ...) \
>   	printk(level pr_fmt("EXPECT_NOT / : ") fmt, ##__VA_ARGS__)
>   
> +/*
> + * Some tests will cause the kernel to emit a stack dump, aka back trace,
> + * when the test is successful.  The tests should make it possible for
> + * test beds to detect that the trace is not an error via EXPECT_BEGIN().
> + *
> + * Most test beds do not process the EXPECT_BEGIN() information and may
> + * flag the stack dump as an error, thus reporting a false failure.  It
> + * is hoped that the KTAP version 4 specification will add the EXPECT_BEGIN()
> + * processing to test beds.
> + *
> + * By default, skip tests that cause a stack dump.  Test beds that process
> + * EXPECT_BEGIN() information should enable these tests via a kernel boot
> + * command line option.
> + */
> +static int stackdump_tests_enabled;
> +
> +static int __init enable_unittest_stackdump(char *str)
> +{
> +	stackdump_tests_enabled = 1;
> +	return 0;
> +}
> +
> +static int __init disable_unittest_stackdump(char *str)
> +{
> +	stackdump_tests_enabled = 0;
> +	return 0;
> +}
> +early_param("of_unittest_stackdump", enable_unittest_stackdump);
> +early_param("no_of_unittest_stackdump", disable_unittest_stackdump);

Does no_of_unittest_stackdump have any benefit or value ?

Thanks,
Guenter