LKML Archive on
help / color / mirror / Atom feed
From: Dmitry Safonov <>
To: "Theodore Y. Ts'o" <>
	Arnd Bergmann <>
Subject: Re: [PATCH 1/2] random: Omit double-printing ratelimit messages
Date: Fri, 11 May 2018 13:41:03 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, 2018-05-10 at 23:51 -0400, Theodore Y. Ts'o wrote:
> On Thu, May 10, 2018 at 08:50:07PM +0100, Dmitry Safonov wrote:
> > random uses __ratelimit() which calls ___ratelimit() with a
> > function
> > name. Depending on !RATELIMIT_MSG_ON_RELEASE it prints how many
> > messages were suppressed every ratelimit interval (1 second for
> > random)
> > and flushes ratelimit_state::missed:
> So the thing about the ratelimit system is that if you have a burst
> of
> 1,000,000 within the one second burst window, and then nothing ever
> again, you will never see a message accounting for those 1,000,000
> "callbacks" (which is a terrible wording; it just confuses people).
> If you have a burst of 1,000,000 calls to ratelimit, and then a month
> goes by, and *then* a single call to __ratelimit is called by printk,
> only *the* does the message about the suppressed "callback" get
> printed.

Yes, if the initialization time of driver is lesser than a second.
If it's 1.1 sec - you'll have prints from ___ratelimit() and from your
driver too. And they differ in format.

> So in the case of the random driver, once the random driver is fully
> intialized, there will never be a call to __ratelimit() for the
> urandom ratelimit structures, so we manually print out the final
> number of suppressed message so there is proper accounting for them.

So, there is this flag, AFAICS, which perfectly fits your purpose
RATELIMIT_MSG_ON_RELEASE which will omit printing how many messages
were suppressed every interval of ___ratelimit(). And that will allow
you to print total in the end.

> It is not a double-count.  If we didn't do that, those suppressed
> warnings would never be mentioned by the kernel.

Yeah, but what you print is not total sum, it's since the last interval
because without mentioned flag ___ratelimit() will flush missed counter
and print "suppressed" message.
They might even double if say other proccess has called
get_random_bytes() got to ___ratelimit() and got preempted. This thread
finishes initializing random driver and prints this not-proper-sum
statistics, and when the code flow is back in the first context, it
will print statistics again from ___ratelimit() function. 


  reply	other threads:[~2018-05-11 12:41 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-10 12:52 [PATCH 0/2] ratelimit: Do not lose messages under limit Dmitry Safonov
2018-05-10 12:52 ` [PATCH 1/2] random: Omit double-printing ratelimit messages Dmitry Safonov
2018-05-10 18:19   ` Theodore Y. Ts'o
2018-05-10 18:37     ` Dmitry Safonov
2018-05-10 19:40       ` Theodore Y. Ts'o
2018-05-10 19:50         ` Dmitry Safonov
2018-05-11  3:51           ` Theodore Y. Ts'o
2018-05-11 12:41             ` Dmitry Safonov [this message]
2018-05-16 15:46               ` Dmitry Safonov
2018-05-16 20:54                 ` Theodore Y. Ts'o
2018-05-16 22:11                   ` Dmitry Safonov
2018-05-10 12:52 ` [PATCH 2/2] lib/ratelimit: Lockless ratelimiting Dmitry Safonov

Reply instructions:

You may reply publicly 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 \ \ \ \ \ \ \
    --subject='Re: [PATCH 1/2] random: Omit double-printing ratelimit messages' \

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

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).