Messages in this thread | | | Date | Fri, 12 Dec 2008 11:48:29 +1100 | From | Paul Mackerras <> | Subject | Re: [PATCH][v2] fork_init: fix division by zero |
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Andrew Morton writes:
> > +#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
The assumption is that THREAD_SIZE is a power of 2, as is PAGE_SIZE.
I think Yuri should be increasing THREAD_SIZE for the larger page sizes he's implementing, because we have on-stack arrays whose size depends on the page size. I suspect that having THREAD_SIZE less than 1/8 of PAGE_SIZE risks stack overflows, and the better fix is for Yuri to make sure THREAD_SIZE is at least 1/8 of PAGE_SIZE. (In fact, more may be needed - someone should work out what fraction is actually needed.)
Paul.
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