[Xen-devel] Re: [rfc] [patch] grant_entry.flags accessors

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 27 Jun 2006, at 17:11, Hollis Blanchard wrote:

> In general I'm skeptical of blindly performing these operations on
> unknown data. I think it's pretty clear that is not a good interface,
> and what you're suggesting is codifying this behavior in the interface.
>
> More practically speaking, I would be shocked if the Linux maintainers
> would accept that sort of change to their atomic interfaces.
I shouldn't imagine they'd mind the interface being made more 
permissive, with no performance loss for the common case and no extra 
API complexity, but anyway: How about add a 
ARCH_SUPPORTS_UNALIGNED_CMPXCHG and move special gnttab_cmpxchg() 
definition to gnttab.c, compilation dependent on that? Or rename the 
gnttab_cmpxchg to synch_cmpxchg_unaligned so at least the name is a bit 
more generic. It could then be used in other contexts.
The Xen change is okay, but gnttab_clear_flag() would be a better 
function name if the function is really going to be gnttab specific. Or 
rename to clear_bit_unaligned and move definition to bitops.h. As with 
synch_cmpxchg_unaligned, the new function could then be used in other 
contexts.
 -- Keir


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