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Subject: Re: [REGRESSION] RLIMIT_DATA crashes named
From: Joe Perches <joe@perches.com>
To: Konstantin Khlebnikov <koct9i@gmail.com>,
        Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Sam Varshavchik <mrsam@courier-mta.com>,
        Ingo Molnar <mingo@kernel.org>, Laura Abbott <labbott@redhat.com>,
        Brent <fix@bitrealm.com>, Andrew Morton <akpm@linux-foundation.org>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Date: Sat, 17 Sep 2016 14:52:31 -0700
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On Sun, 2016-09-18 at 00:40 +0300, Konstantin Khlebnikov wrote:
> #define printk_periodic(period, fmt, ...)
> ({
>         static unsigned long __prev __read_mostly = INITIAL_JIFFIES - (period);
>         unsigned long __now = jiffies;
>         bool __print = !time_in_range_open(__now, __prev, __prev + (period));
> 
>         if (__print) {
>                 __prev = __now;
>                 printk(fmt, ##__VA_ARGS__);
>         }
>         unlikely(__print);
> })

printk_periodic reads like a thing that would create a
thread to printk a message every period.

And trivially, period should be copied to a temporary
and not be reused (use your choice of # of underscores)

	unsigned long _period = period;
	unsigned long _now = now;
	static unsigned long _prev __read_mostly = etc...