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Date: Sat, 17 Sep 2016 12:09:41 +0300
From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Joe Perches <joe@perches.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [REGRESSION] RLIMIT_DATA crashes named
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On Sat, Sep 17, 2016 at 11:33:56AM +0300, Konstantin Khlebnikov wrote:
> >
> > do_just_once just isn't a good name for a global
> > rate limited mechanism that does something very
> > different than the name.
> >
> > Maybe allow_once_per_ratelimit or the like
> >
> > There could be an equivalent do_once
> >
> > https://lkml.org/lkml/2009/5/22/3
> >
> 
> What about this printk_reriodic() and pr_warn_once_per_minute()?
> 
> It simply remembers next jiffies to print rather than using that
> complicated ratelimiting engine.

+#define printk_periodic(period, fmt, ...)                      \
+({                                                             \
+	static unsigned long __print_next __read_mostly = INITIAL_JIFFIES; \
+	bool __do_print = time_after_eq(jiffies, __print_next); \
+                                                               \
+	if (__do_print) {                                       \
+               __print_next = jiffies + (period);              \
+               printk(fmt, ##__VA_ARGS__);                     \
+	}                                                       \
+	unlikely(__do_print);                                   \
+})

Seems I don't understand the bottom unlikely...