From: "Theodore Ts'o" <tytso@mit.edu>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Mackall <mpm@selenic.com>,
Linux Kernel Developers List <linux-kernel@vger.kernel.org>,
w@1wt.eu, ewust@umich.edu, zakir@umich.edu, greg@kroah.com,
nadiah@cs.ucsd.edu, jhalderm@umich.edu, tglx@linutronix.de,
davem@davemloft.net, stable@kernel.org
Subject: Re: [PATCH 01/10] random: make 'add_interrupt_randomness()' do something sane
Date: Fri, 6 Jul 2012 09:01:27 -0400 [thread overview]
Message-ID: <20120706130127.GB10798@thunk.org> (raw)
In-Reply-To: <CA+55aFxhobNMY5RLmH+tKox8voqfH-bVqKVF03JeeVrHkhLcaQ@mail.gmail.com>
On Thu, Jul 05, 2012 at 07:59:00PM -0700, Linus Torvalds wrote:
> On Thu, Jul 5, 2012 at 4:21 PM, Theodore Ts'o <tytso@mit.edu> wrote:
> > On Thu, Jul 05, 2012 at 05:31:22PM -0500, Matt Mackall wrote:
> >>
> >> It's better to mix and not credit than to not mix at all. Instead just
> >> check the fast count against HZ before the credit.
> >
> > I'm not sure what you mean by this?
>
> So what I think Matt meant was to check number of timer interrupts
> against the fast count.
>
> IOW, always call "add_interrupt_randomness()", but then in that
> function, when you determine the amount of entropy, check if there
> were non-timer interrupts in the last HZ cycle. If there were purely
> timer interrupts, you can still mix in the cycle information, but it's
> likely to be fairly weak.
I'm going to have to plead ignorance to how the timer code works these
days. With the advent of clockevents and NOHZ, it's gotten a lot more
complicated. What in the world is "fast count"? I've grepped for it,
and I can't find it.
I can simply not credit entropy of the timer is on the irq, but I
think you and Matt were suggesting more subtle. I just have no idea
how to tell if there were non-timer interrupts during the last HZ
cycle. Can you give me a hint?
Thanks,
- ted
next prev parent reply other threads:[~2012-07-06 13:01 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-05 18:12 [PATCH 00/10] /dev/random fixups Theodore Ts'o
2012-07-05 18:12 ` [PATCH 01/10] random: make 'add_interrupt_randomness()' do something sane Theodore Ts'o
2012-07-05 18:47 ` Matt Mackall
2012-07-05 18:52 ` Linus Torvalds
2012-07-05 21:39 ` Matt Mackall
2012-07-05 21:47 ` Linus Torvalds
2012-07-05 22:00 ` Theodore Ts'o
2012-07-05 22:21 ` Linus Torvalds
2012-07-05 22:31 ` Matt Mackall
2012-07-05 22:35 ` Linus Torvalds
2012-07-05 23:21 ` Theodore Ts'o
2012-07-06 2:59 ` Linus Torvalds
2012-07-06 13:01 ` Theodore Ts'o [this message]
2012-07-06 16:24 ` Linus Torvalds
2012-07-06 16:52 ` Theodore Ts'o
2012-07-09 19:15 ` Matt Mackall
2012-07-25 18:43 ` Thomas Gleixner
[not found] ` <CAGsuqq2MWuFnY7PMb_2ddBNNJr80xB_JW+Wryq3mhhmQuEojpg@mail.gmail.com>
2012-07-06 21:59 ` Theodore Ts'o
2012-07-05 18:12 ` [PATCH 02/10] random: use lockless techniques when mixing entropy pools Theodore Ts'o
2012-07-05 18:18 ` Linus Torvalds
2012-07-05 18:19 ` Greg KH
2012-07-05 23:09 ` Theodore Ts'o
2012-07-05 19:10 ` Matt Mackall
2012-07-05 19:47 ` Theodore Ts'o
2012-07-05 20:45 ` Matt Mackall
2012-07-05 18:12 ` [PATCH 03/10] random: create add_device_randomness() interface Theodore Ts'o
2012-07-05 18:12 ` [PATCH 04/10] usb: feed USB device information to the /dev/random driver Theodore Ts'o
2012-07-05 18:12 ` [PATCH 05/10] net: feed /dev/random with the MAC address when registering a device Theodore Ts'o
2012-07-05 18:12 ` [PATCH 06/10] random: use the arch-specific rng in xfer_secondary_pool Theodore Ts'o
2012-07-05 18:49 ` Linus Torvalds
2012-07-05 18:12 ` [PATCH 07/10] random: add new get_random_bytes_arch() function Theodore Ts'o
2012-07-05 18:35 ` Linus Torvalds
2012-07-05 19:50 ` Theodore Ts'o
2012-07-05 21:45 ` Matt Mackall
2012-07-25 3:37 ` H. Peter Anvin
2012-07-25 7:22 ` Ingo Molnar
2012-07-25 15:10 ` Theodore Ts'o
2012-07-25 15:19 ` H. Peter Anvin
2012-07-25 17:37 ` [PATCH] random: mix in architectural randomness in extract_buf() H. Peter Anvin
2012-07-25 23:50 ` Ben Hutchings
2012-07-26 0:32 ` H. Peter Anvin
2012-07-28 2:39 ` Theodore Ts'o
2012-07-28 2:48 ` H. Peter Anvin
2012-07-26 3:16 ` [PATCH 07/10] random: add new get_random_bytes_arch() function H. Peter Anvin
2012-07-26 3:24 ` H. Peter Anvin
2012-07-05 18:12 ` [PATCH 08/10] random: unify mix_pool_bytes() and mix_pool_bytes_entropy() Theodore Ts'o
2012-07-05 18:12 ` [PATCH 09/10] random: add tracepoints for easier debugging and verification Theodore Ts'o
2012-07-05 18:12 ` [PATCH 10/10] MAINTAINERS: Theodore Ts'o is taking over the random driver Theodore Ts'o
2012-07-06 11:40 ` [PATCH 00/10] /dev/random fixups Fengguang Wu
2012-07-06 12:44 ` Theodore Ts'o
2012-07-20 20:15 ` [PATCH] dmi: Feed DMI table to /dev/random driver Tony Luck
2012-07-20 21:03 ` Matt Mackall
2012-07-21 0:56 ` Theodore Ts'o
2012-07-21 1:19 ` Tony Luck
2012-07-21 2:02 ` Theodore Ts'o
2012-07-23 16:47 ` [PATCH] random: Add comment to random_initialize() Tony Luck
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