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From: Petr Mladek <pmladek@suse.com>
To: Thierry Escande <thierry.escande@linaro.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	David Miller <davem@davemloft.net>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	"Tobin C . Harding" <me@tobin.cc>,
	linux-kernel@vger.kernel.org,
	Andy Shevchenko <andy.shevchenko@gmail.com>
Subject: Re: [PATCH RESEND] lib/test_printf.c: call wait_for_random_bytes() before plain %p tests
Date: Fri, 8 Jun 2018 10:04:37 +0200	[thread overview]
Message-ID: <20180608080437.n2b5nv73d3kp6yhb@pathway.suse.cz> (raw)
In-Reply-To: <d9ecdf72-7500-66d4-0360-231218cccbb4@linaro.org>

On Thu 2018-06-07 20:47:25, Thierry Escande wrote:
> Hi Petr,
> 
> On 07/06/2018 14:24, Petr Mladek wrote:
> > On Mon 2018-06-04 13:37:08, Thierry Escande wrote:
> > > If the test_printf module is loaded before the crng is initialized, the
> > > plain 'p' tests will fail because the printed address will not be hashed
> > > and the buffer will contain '(ptrval)' instead.
> > > This patch adds a call to wait_for_random_bytes() before plain 'p' tests
> > > to make sure the crng is initialized.
> > 
> > Hmm, my system did not boot with this patch and
> > CONFIG_TEST_PRINTF=y
> > 
> > I guess that there was not enough entropy. It is basically a deadlock.
> > The build-in module init calls are called when SMP is enabled but
> > there is no real activity and the init calls are called sequentially.
> > Therefore there is nothing that could produce some entropy, ...
> > 
> > I suggest to skip the test when crng is not ready.
> 
> Thanks for pointing this out.
> 
> The issue is that the crng_ready() is not available outside of random.c.
> I'll leave the call to wait_for_random_bytes() if test_printf is compiled as
> a module and use add_random_ready_callback() to check if crng is initialized
> otherwise. Does that sound ok to you?

Great, I was not aware of add_random_ready_callback().

I suggest to make the decision in test_printf_init()
and run all tests either as the callback or immediately.

Best Regards,
Petr

  reply	other threads:[~2018-06-08  8:04 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-04 11:37 Thierry Escande
2018-06-05 12:43 ` Andy Shevchenko
2018-06-07 12:24 ` Petr Mladek
2018-06-07 18:47   ` Thierry Escande
2018-06-08  8:04     ` Petr Mladek [this message]
2018-06-08  9:07       ` Thierry Escande
2018-06-08  9:46         ` Andy Shevchenko
2018-06-08 10:32           ` Thierry Escande
2018-06-08 11:22             ` Petr Mladek
2018-06-08 11:28               ` Thierry Escande
2018-06-22 20:53   ` Steven Rostedt
2018-06-22 21:50     ` Thierry Escande
2018-06-25  7:50       ` Petr Mladek
2018-06-25 12:04         ` Petr Mladek

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