From: James Hogan <redacted>
Date: Mon, 17 Dec 2012 09:51:04 +0000

On 10/12/12 12:55, Geert Uytterhoeven wrote:

quoted

On Mon, Dec 10, 2012 at 11:22 AM, James Hogan [off-list ref] wrote:

quoted

On 08/12/12 03:43, H. Peter Anvin wrote:

quoted

On 12/05/2012 08:08 AM, James Hogan wrote:

quoted

On 64 bit architectures with no efficient unaligned access, taskstats
has to add some padding to a reply to prevent unaligned access warnings.
However this also needs to apply to 32 bit architectures with 64 bit
struct alignment such as metag (which has 64 bit memory accesses).

Wait... 64-bit struct alignment on structures with only 32-bit members?
 That might be... interesting... in a number of places...

I'll rewrite the description as it's a bit misleading. On metag 64bit
struct alignment is required when it contains 64bit members, not if it
only contains 32bit members. Although metag is a 32bit arch, it can do
64bit memory accesses which must be aligned.

The C alignment rules should take care of this automatically (struct alignment
is the maximum alignment of its members).

Hi Geert,

Please see the comment in mk_reply in kernel/taskstats.c. The structure
is being serialised after 2 NLA headers and a pid which is why the extra
padding needs to be added manually.

Please solve netlink attribute 64-bit alignment issues fundamentally
rather on a case-by-case basis.

We were just discussing this very issue on the netdev list recently,
CC:'d