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

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Date:   Wed, 17 Jul 2019 09:36:13 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Herbert Xu <herbert@...dor.apana.org.au>
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

Quoting Herbert Xu (2019-07-16 18:43:59)
> 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.
> 

Sure. I'll resend just this one Cced to the linux-crypto list and to
you.