linux-kernel - Re: [PATCH 1/2] random: Omit double-printing ratelimit messages

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Date:   Thu, 10 May 2018 20:50:07 +0100
From:   Dmitry Safonov <dima@...sta.com>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     linux-kernel@...r.kernel.org, 0x7f454c46@...il.com,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 1/2] random: Omit double-printing ratelimit messages

On Thu, 2018-05-10 at 15:40 -0400, Theodore Y. Ts'o wrote:
> On Thu, May 10, 2018 at 07:37:40PM +0100, Dmitry Safonov wrote:
> > 
> > Ok, then what's the purpose of those messages?
> > :        pr_notice("random: %d get_random_xx warning(s) missed "
> > :                  "due to ratelimiting\n",
> > :                  unseeded_warning.missed);
> > :        pr_notice("random: %d urandom warning(s) missed "
> > :                  "due to ratelimiting\n",
> > :                  urandom_warning.missed);
> > 
> > I thought you want to print the summary after initializing random,
> > not once per second?
> 
> Yes, and that's what is happening today.  The "output lines
> suppressed
> due to ratelimiting" message is only printed out by
> printk_ratelimit()
> function, which we are *not* using.

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:

:if (time_is_before_jiffies(rs->begin + rs->interval)) {
:    if (rs->missed) {
:        if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
:            printk_deferred(KERN_WARNING
:                            "%s: %d callbacks suppressed\n",
:                            func, rs->missed);
:            rs->missed = 0;
:        }
:    }
:    rs->begin   = jiffies;
:    rs->printed = 0;
:}

-- 
Thanks,
             Dmitry