linux-kernel - Re: [PATCH v2 1/6] hwrng: core: Freeze khwrng thread during suspend

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Message-ID: <20190717014359.5xcnubpmazl3vqg5@gondor.apana.org.au>
Date:   Wed, 17 Jul 2019 09:43:59 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Peter Huewe <peterhuewe@....de>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, Jason Gunthorpe <jgg@...pe.ca>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-integrity@...r.kernel.org,
        Andrey Pronin <apronin@...omium.org>,
        Duncan Laurie <dlaurie@...omium.org>,
        Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH v2 1/6] hwrng: core: Freeze khwrng thread during suspend

On Tue, Jul 16, 2019 at 03:45:13PM -0700, Stephen Boyd wrote:
> The hwrng_fill() function can run while devices are suspending and
> resuming. If the hwrng is behind a bus such as i2c or SPI and that bus
> is suspended, the hwrng may hang the bus while attempting to add some
> randomness. It's been observed on ChromeOS devices with suspend-to-idle
> (s2idle) and an i2c based hwrng that this kthread may run and ask the
> hwrng device for randomness before the i2c bus has been resumed.
> 
> Let's make this kthread freezable so that we don't try to touch the
> hwrng during suspend/resume. This ensures that we can't cause the hwrng
> backing driver to get into a bad state because the device is guaranteed
> to be resumed before the hwrng kthread is thawed.
> 
> Cc: Andrey Pronin <apronin@...omium.org>
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Cc: Duncan Laurie <dlaurie@...omium.org>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>  drivers/char/hw_random/core.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)

Do you want this to go through the crypto tree? If so you need
to cc the linux-crypto mailing list.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt