Subject: Re: [PATCH][v2] fork_init: fix division by zero

From: Al Viro <[email-masked]>
Date: Thu, 11 Dec 2008 20:28:00 +0000

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?