Re: [tip:x86/mm] x86, mm: Use a bitfield to mask nuisance get_user() warnings

From: Linus Torvalds
Date: Mon Feb 11 2013 - 23:43:05 EST

On Mon, Feb 11, 2013 at 8:21 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 02/11/2013 07:33 PM, Linus Torvalds wrote:
>> Has anybody run this past any gcc developers? And if so, did they run
>> away screaming?
> I haven't no... H.J., any comments on this patch?

I'd be most worried about any known pitfalls about bitfield code
generation. Looking at your code size numbers, it actually seems to
*improve* code generation except for the odd i386.pae case (bigger
code but also a different data size - odd) and i386 noconfig
(different bss, bigger code).

The code/data changes makes me wonder if the variable sometimes gets
flushed to memory as a 8-byte entry, and maybe there are things gcc
people can suggest..

But I don't see anything fundamentally wrong with it. Certainly it
looks much better than the disgusting and warning-prone

unsigned long long __val_gu8


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at