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Subject: Re: [PATCH RESEND] lib/test_printf.c: call wait_for_random_bytes()
 before plain %p tests
To:     Petr Mladek <pmladek@suse.com>
Cc:     Andy Shevchenko <andy.shevchenko@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Miller <davem@davemloft.net>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        "Tobin C . Harding" <me@tobin.cc>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <20180604113708.11554-1-thierry.escande@linaro.org>
 <20180607122434.i4x7b5ij4p6dpx7w@pathway.suse.cz>
 <d9ecdf72-7500-66d4-0360-231218cccbb4@linaro.org>
 <20180608080437.n2b5nv73d3kp6yhb@pathway.suse.cz>
 <0fa30e13-c16f-95d8-d1ef-fd45e7a99888@linaro.org>
 <CAHp75Vc5_+Kxsvgws9Oq-hOgbQ8-ocxeKa4AuhC0uJ0oKsu+BA@mail.gmail.com>
 <a8ab166e-a2b9-b0fc-9717-ffd8fcbcd386@linaro.org>
 <20180608112230.77zsd5y7we7hiqei@pathway.suse.cz>
From:   Thierry Escande <thierry.escande@linaro.org>
Message-ID: <5484aaf1-ec14-0013-c2c1-fcb3e95b975d@linaro.org>
Date:   Fri, 8 Jun 2018 13:28:58 +0200
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On 08/06/2018 13:22, Petr Mladek wrote:
> On Fri 2018-06-08 12:32:33, Thierry Escande wrote:
>> On 08/06/2018 11:46, Andy Shevchenko wrote:
>>> On Fri, Jun 8, 2018 at 12:07 PM, Thierry Escande
>>> <thierry.escande@linaro.org> wrote:
>>>
>>>> But as I type I realize it's not necessary. I will simply enclose the call
>>>> to wait_for_random_bytes() by #if IS_MODULE() #endif so it gets called only
>>>> if built as a module, which is how run_kselftest.sh wants it... If
>>>> test_printf is compiled built-in and the crng is not yet initialized the
>>>> test will fail anyway so there is no need to add an extra check.
>>>
>>> Unfortunately I can't support this as is.
>>> We have environments where crng will be ready minutes after the boot.
>>> It's unacceptable.
>>>
>>> So, we need to have means to not delay test for so long.
>>
>> I agree we can't delay test execution for too long. In my case the crng is
>> ready only a few seconds after the boot. So we may just skip this plain 'p'
>> printf test if crng is not ready then.
> 
> Alternative solution would be to accept
> const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)";
> as a valid result. It would make sense to print some warning in that case.
> 
> In each case, it would look ugly to use add_random_ready_callback()
> wihtout passing a callback. If you really needed to check crng_ready(),
> it would be better to make it public.

Agree but even with crng_ready() public we would have to block the test 
until it's ready which is not good either.

Accepting "(ptrval)" as a valid result seems the least bad alternative...

Regards,
Thierry