Re: [Xen-devel] RFC: 32 bits as smallest atomic size.

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

I expect we can fix that up in the ppc macros: if the atomic access is 
sub-32-bit aligned then round the address down to 32-bit boundary and 
do a 32-bit cmpxchg.
 -- Keir

On 25 Mar 2005, at 21:25, Jimi Xenidis wrote:

> In PPC land we have an issue where cmpxchg operations can only be
> applied to strictly aligned 32 and 64 bit quantities.
>
> We understand on x86 the use of the packed attribute has certain
> benefits, but in the common areas we believe that portability should
> be the primary concern in the common code.
>
> I can only assume that much debate will come from this as we find
> alignment and size issues all over.
>
> The particular offender at the moment is:
>   include/public/grant_table.h flags 76 u16 flags;
>
> It is used with atomic methods such as cmpxchg_user() and clear_bit().
>
> Any thoughts on how to proceed with this would be appreciated.
>
> -JX
>
> BTW: is clear_bit() as implemeted for x86 have soem alignment issues?
> My expertise in this space is limited.
>
>
>
>
>
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