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From: Ingo Molnar <mingo@kernel.org>
To: Mark Brown <broonie@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H . Peter Anvin" <hpa@zytor.com>,
	Andy Lutomirski <luto@amacapital.net>,
	linux-kernel@vger.kernel.org, x86@kernel.org,
	linux-kselftest@vger.kernel.org, Dan Rue <dan.rue@linaro.org>
Subject: Re: [PATCH 2/2] selftests/x86/fsgsbase: Default to trying to run the test repeatedly
Date: Mon, 11 Feb 2019 09:49:16 +0100	[thread overview]
Message-ID: <20190211084916.GB62722@gmail.com> (raw)
In-Reply-To: <20190203134017.9375-3-broonie@kernel.org>


* Mark Brown <broonie@kernel.org> wrote:

> In automated testing it has been found that on many systems the fsgsbase
> test fails intermittently.  This was reported and discussed a while
> back:
> 
>     https://lore.kernel.org/lkml/20180126153631.ha7yc33fj5uhitjo@xps/
> 
> with the analysis concluding that this is a hardware issue affecting a
> subset of systems but no fix has been merged as yet.  As well as the
> actual problem found by testing the intermittent test failure is causing
> issues for the people doing the automated testing due to the noise.
> 
> In order to make the testing stable modify the test program to iterate
> through the test repeatedly, choosing 5000 iterations based on prior
> reports and local testing.  This unfortunately greatly increases the
> execution time for the selftests when things succeed which isn't great,
> in my local tests on a range of systems it pushes the execution time up
> to approximately a minute when no failures are encountered.
> 
> Reported-by: Dan Rue <dan.rue@linaro.org>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
>  tools/testing/selftests/x86/fsgsbase.c | 27 +++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/x86/fsgsbase.c b/tools/testing/selftests/x86/fsgsbase.c
> index 6cda6daa1f8c..83410749ff1f 100644
> --- a/tools/testing/selftests/x86/fsgsbase.c
> +++ b/tools/testing/selftests/x86/fsgsbase.c
> @@ -379,7 +379,7 @@ static void test_unexpected_base(void)
>  	}
>  }
>  
> -int main()
> +int test()
>  {
>  	pthread_t thread;
>  
> @@ -437,3 +437,28 @@ int main()
>  
>  	return nerrs == 0 ? 0 : 1;
>  }
> +
> +int main()
> +{
> +	int tries = 5000;
> +	int i;
> +
> +	if (tries > 1)
> +		quiet = true;
> +
> +	for (i = 0; i < tries; i++) {
> +		if (test() != 0)
> +			break;
> +	}
> +
> +	if (quiet) {
> +		if (nerrs) {
> +			printf("[FAIL] %d errors detected in %d tries\n",
> +				nerrs, i + 1);
> +		} else {
> +			printf("[PASS] %d runs succeeded\n", i);
> +		}
> +	}
> +
> +	return nerrs == 0 ? 0 : 1;
> +}

So this isn't very user-friendly either, previously it would run a 
testcase and immediately provide output.

Now it's just starting and 'hanging':

  galatea:~/linux/linux/tools/testing/selftests/x86> ./fsgsbase_64 

I got bored and Ctrl-C-ed it after ~30 seconds.

How long is this supposed to run, and why isn't the user informed?

Also, testcases should really be short, so I think a better approach 
would be to thread the test-case and start an instance on every CPU. That 
should also excercise SMP bugs, if any.

Thanks,

	Ingo

  reply	other threads:[~2019-02-11  8:49 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-03 13:40 [PATCH 0/2] Make fsgsbase test more stable Mark Brown
2019-02-03 13:40 ` [PATCH 1/2] selftests/x86/fsgsbase: Indirect output through a wrapper function Mark Brown
2019-02-11  8:45   ` Ingo Molnar
2019-02-11 13:02     ` Mark Brown
2019-02-03 13:40 ` [PATCH 2/2] selftests/x86/fsgsbase: Default to trying to run the test repeatedly Mark Brown
2019-02-11  8:49   ` Ingo Molnar [this message]
2019-02-11 12:47     ` Mark Brown
2019-02-11 12:51       ` Ingo Molnar

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