Re: Reduce struct page by 8 bytes on 64bit

[Andi Kleen <ak@muc.de>]

On Wed, Apr 16, 2003 at 02:45:21PM +0200, David S. Miller wrote:
>    From: Andi Kleen <ak@muc.de>
>    Date: Tue, 15 Apr 2003 13:24:30 +0200
>    
>    I worked around this by declaring a new data type atomic_bitmask32
>    with matching set_bit32/clear_bit32 etc. interfaces. Currently only 
>    on x86-64 aomitc_bitmask32 is defined to unsigned, everybody else
>    still uses unsigned long. The other 64bit architectures can define it to
>    unsigned too if they can confirm that it's ok to do.
> 
> I have no problem with this.
> 
> If you are clever, you can define a generic version even for the
> "unsigned long" 64-bit platforms.  It's left as an exercise to
> the reader :-)

How so? Of course I could write an generic set_bit32, but the question
is if these bit operations would be still atomic on SMP and not conflict with
fields occuping the same 8 byte slot. I remember you flaming someone 
some time ago because he used set_bit in an atomic fashion on a type smaller
than unsigned long for example.

-Andi