Linux-Crypto Archive on
 help / color / Atom feed
From: "Maciej S. Szmigiero" <>
To: Stephen Boyd <>
Cc: Herbert Xu <>,,,
	Andrey Pronin <>,
	Duncan Laurie <>,
	Jason Gunthorpe <>, Arnd Bergmann <>,
	Greg Kroah-Hartman <>,
	Guenter Roeck <>,
	Alexander Steffen <>
Subject: Re: [PATCH v3] hwrng: core: Freeze khwrng thread during suspend
Date: Tue, 29 Oct 2019 00:45:31 +0100
Message-ID: <> (raw)
In-Reply-To: <>

Hi Stephen,

On 06.08.2019 01:32, 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.

This patch broke suspend with virtio-rng loaded (it hangs).

The problematic call chain is:
virtrng_freeze() -> remove_common() -> hwrng_unregister() ->

It looks like kthread_stop() can't finish on a frozen khwrng thread.

Reverting this commit makes a VM with virtio-rng driver loaded
suspend and resume correctly again.


  parent reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-05 23:32 Stephen Boyd
2019-08-06 15:01 ` Stephen Boyd
2019-08-15 12:06 ` Herbert Xu
2019-10-28 23:45 ` Maciej S. Szmigiero [this message]
     [not found]   ` <>
2019-10-29 15:50     ` Maciej S. Szmigiero
     [not found]       ` <>
2019-11-10  0:30         ` Maciej S. Szmigiero

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Crypto Archive on

Archives are clonable:
	git clone --mirror linux-crypto/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-crypto linux-crypto/ \
	public-inbox-index linux-crypto

Example config snippet for mirrors

Newsgroup available over NNTP:

AGPL code for this site: git clone