Re: [PATCH v3] hwrng: core: Freeze khwrng thread during suspend

From: Herbert Xu
Date: Thu Aug 15 2019 - 08:06:17 EST

On Mon, Aug 05, 2019 at 04:32:41PM -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@xxxxxxxxxxxx>
> Cc: Duncan Laurie <dlaurie@xxxxxxxxxxxx>
> Cc: Jason Gunthorpe <jgg@xxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Guenter Roeck <groeck@xxxxxxxxxxxx>
> Cc: Alexander Steffen <Alexander.Steffen@xxxxxxxxxxxx>
> Signed-off-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
> ---
> I'm splitting this patch off of the larger series so it can
> go through the crypto tree. See [1] for the prevoius round.
> Nothing has changed in this patch since then.
> [1]
> drivers/char/hw_random/core.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)

Patch applied. Thanks.
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
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