Re: [x86 patch] Fix UML signal.h build errors

[Al Viro <viro@ftp.linux.org.uk>]

On Thu, Oct 25, 2007 at 09:01:52PM +0530, Balbir Singh wrote:

> Thats nice, I wonder why I missed them searching on lkml in my gmail box
> :(
> 
> Is __arch_um__ the right thing to do or BITS_PER_LONG == 32? I prefer
> BITS_PER_LONG == 32 over #if defined(__i386__) || defined(__arch__um__).
> I guess its a matter of personal preference.

Huh?

a) we really shouldn't mess with compiler defines (i.e. we should not
undef __i386__ or __x86_64__)

b) I'd rather have __arch_um__ mentioned explicitly in 3 places where
we do care about difference between i386 and uml/i386 than have certain
to be forgotten rules for places like include/asm-x86

c) if you look at those places, you'll see
	* drivers/char/mem.c::uncached_access().  Really per-architecture
and I wonder if it might be include/asm-* fodder...
	* kernel/signal.c debugging printks.  Should die or be sanitized, IMO.
	* raid6 algorithms.  Hell knows - immediate reason why we don't do
those on uml is the lack of kernel_fpu_begin()/kernel_fpu_end() (and
boot_cpu_has(), but that's easier to add).  Do we care to implement that
stuff?

That's _all_.  Nothing else has to care.