From: Al Viro <viro@ZenIV.linux.org.uk>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: wd@denx.de, dzu@denx.de, linux-kernel@vger.kernel.org,
linuxppc-dev@ozlabs.org, miltonm@bga.com,
Geert.Uytterhoeven@sonycom.com, yanok@emcraft.com
Subject: Re: [PATCH][v2] fork_init: fix division by zero
Date: Thu, 11 Dec 2008 20:28:00 +0000 [thread overview]
Message-ID: <20081211202800.GQ28946@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20081211121635.ff58193f.akpm@linux-foundation.org>
On Thu, Dec 11, 2008 at 12:16:35PM -0800, Andrew Morton wrote:
> > +#if (8 * THREAD_SIZE) > PAGE_SIZE
> > max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
> > +#else
> > + max_threads = mempages * (PAGE_SIZE / (8 * THREAD_SIZE));
> > +#endif
>
> The expression you've chosen here can be quite inacccurate, because
> ((PAGE_SIZE / (8 * THREAD_SIZE)) is a small number. The way to
> preserve accuracy is
>
> max_threads = (mempages * PAGE_SIZE) / (8 * THREAD_SIZE);
>
> so how about avoiding the nasty ifdefs and doing
Are you sure? Do they actually cross the page boundaries?
WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Yuri Tikhonov <yur@emcraft.com>,
linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org,
Geert.Uytterhoeven@sonycom.com, dhowells@redhat.com,
miltonm@bga.com, wd@denx.de, dzu@denx.de, yanok@emcraft.com
Subject: Re: [PATCH][v2] fork_init: fix division by zero
Date: Thu, 11 Dec 2008 20:28:00 +0000 [thread overview]
Message-ID: <20081211202800.GQ28946@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20081211121635.ff58193f.akpm@linux-foundation.org>
On Thu, Dec 11, 2008 at 12:16:35PM -0800, Andrew Morton wrote:
> > +#if (8 * THREAD_SIZE) > PAGE_SIZE
> > max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE);
> > +#else
> > + max_threads = mempages * (PAGE_SIZE / (8 * THREAD_SIZE));
> > +#endif
>
> The expression you've chosen here can be quite inacccurate, because
> ((PAGE_SIZE / (8 * THREAD_SIZE)) is a small number. The way to
> preserve accuracy is
>
> max_threads = (mempages * PAGE_SIZE) / (8 * THREAD_SIZE);
>
> so how about avoiding the nasty ifdefs and doing
Are you sure? Do they actually cross the page boundaries?
next prev parent reply other threads:[~2008-12-11 20:28 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-10 16:50 [PATCH][v2] fork_init: fix division by zero Yuri Tikhonov
2008-12-10 16:50 ` Yuri Tikhonov
2008-12-11 20:16 ` Andrew Morton
2008-12-11 20:16 ` Andrew Morton
2008-12-11 20:28 ` Al Viro [this message]
2008-12-11 20:28 ` Al Viro
2008-12-11 20:43 ` Andrew Morton
2008-12-11 20:43 ` Andrew Morton
2008-12-12 2:31 ` Nick Piggin
2008-12-12 2:31 ` Nick Piggin
2008-12-12 2:47 ` Andrew Morton
2008-12-12 2:47 ` Andrew Morton
2008-12-12 3:36 ` Nick Piggin
2008-12-12 3:36 ` Nick Piggin
2008-12-11 22:22 ` Re[2]: " Yuri Tikhonov
2008-12-11 22:22 ` Yuri Tikhonov
2008-12-11 22:26 ` Andrew Morton
2008-12-11 22:26 ` Andrew Morton
2008-12-12 0:48 ` Paul Mackerras
2008-12-12 0:48 ` Paul Mackerras
2008-12-12 1:07 ` Andrew Morton
2008-12-12 1:07 ` Andrew Morton
2008-12-18 7:47 ` Yuri Tikhonov
2008-12-18 7:47 ` Yuri Tikhonov
2008-12-18 22:45 ` Andrew Morton
2008-12-18 22:45 ` Andrew Morton
2008-12-19 5:49 ` Re[2]: " Yuri Tikhonov
2008-12-19 5:49 ` Yuri Tikhonov
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