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Date: Thu, 17 Jul 2008 12:53:31 -0700
From: Julian Elischer <julian@elischer.org>
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To: "Murty, Ravi" <ravi.murty@intel.com>
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Cc: freebsd-hackers@freebsd.org
Subject: Re: atomic_load_acq_int in ipi_nmi_handler()
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Murty, Ravi wrote:
> Hello All,
> 
>  
> 
> Just a quick question: Why does this function (ipi_nmi_handler) execute
> a atomic_load_acq_int(&ipi_nmi_pending). Following this it calls
> atomic_clear_int to clear itself out of this mask. I can't think of why
> the CPU would reorder these instructions knowing there is a dependency
> here.
> 
>  
> 
> Also, since FreeBSD has masks (like ipi_nmi_pending), has there been any
> work on extending this beyond 64 CPUs?

Only in discussion. A quick survey of other OS's and their
answers is probably in order. There are cpu bitmasks in use..

We are going to have to look at the whole NUMA thing soon too.

(BTW it's only 32 on 32 bit machines I believe)

> 
>  
> 
> Thanks
> 
> Ravi
> 
>  
> 
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