Date: Mon, 23 Feb 2015 22:10:02 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Aaron Tomlin <atomlin@redhat.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Davidlohr Bueso <dave@stgolabs.net>,
        David Rientjes <rientjes@google.com>,
        "David S. Miller" <davem@davemloft.net>,
        Fabian Frederick <fabf@skynet.be>, Guenter Roeck <linux@roeck-us.net>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>,
        Jens Axboe <axboe@fb.com>, Joe Perches <joe@perches.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Kees Cook <keescook@chromium.org>,
        Michael Marineau <mike@marineau.org>, Oleg Nesterov <oleg@redhat.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Prarit Bhargava <prarit@redhat.com>, Rik van Riel <riel@redhat.com>,
        Rusty Russell <rusty@rustcorp.com.au>,
        Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vladimir Davydov <vdavydov@parallels.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4 v4] kernel/fork.c: avoid division by zero
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On Mon, Feb 23, 2015 at 09:14:35PM +0100, Heinrich Schuchardt wrote:
> With 32-bit calculus there is no solution which delivers valid results
> for all possible combinations of the parameters.

So I can't help but be bugged by this (my problem I know); calculus is
the mathematics of change; its differential equations and integrals.

What we do here is modular arithmetic on a commutative ring.

Please use calculation as you do here:

> Hence a 64-bit calculation can be used as solution.

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