[PATCH] Use definition for cmpxchg swi

[Russell King - ARM Linux]

On Mon, Nov 09, 2009 at 09:56:26AM -0500, Nicolas Pitre wrote:
> On Mon, 9 Nov 2009, Russell King - ARM Linux wrote:
> 
> > On Sun, Nov 08, 2009 at 08:42:51PM -0500, Nicolas Pitre wrote:
> > > On Sun, 8 Nov 2009, Russell King - ARM Linux wrote:
> > > 
> > > > Use a definition for the cmpxchg SWI instead of hard-coding the number.
> > > 
> > > Well...  Initially I didn't use a definition in unistd.h because I 
> > > didn't want user space to "see" it and assume this was part of the 
> > > kernel ABI since this is actually just an implementation detail that 
> > > depends on a particular kernel configuration.
> > 
> > The ifdef __KERNEL__ is sufficient for that - kernel headers are now
> > stripped of code within these defines during 'make installheaders'.
> 
> Sure. But I wouldn't be surprised to see people redefining it manually 
> just because they didn't understand why there was a #ifdef __KERNEL__ in 
> the kernel file.  Adding a comment makes the intent clearer.

One solution to that would be to make it a random number within a
certain range picked at kernel boot time. ;)

I'll add a comment then.

Note, however, that the original code was buggy - it resulted in
the '0xfff0' syscall being called instead of '0xffff0' - note the
extra 4 bits there.