linux-kernel - Re: [REGRESSION] RLIMIT

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Date:   Sat, 17 Sep 2016 14:52:31 -0700
From:   Joe Perches <joe@...ches.com>
To:     Konstantin Khlebnikov <koct9i@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Sam Varshavchik <mrsam@...rier-mta.com>,
        Ingo Molnar <mingo@...nel.org>,
        Laura Abbott <labbott@...hat.com>, Brent <fix@...realm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [REGRESSION] RLIMIT_DATA crashes named

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...