Re: [PATCH v3 16/34] xen/lib: introduce generic find next bit operations

[Oleksii <oleksii.kurochko@xxxxxxxxx>]

On Fri, 2024-01-26 at 10:48 +0100, Jan Beulich wrote:
> On 26.01.2024 10:44, Oleksii wrote:
> > On Tue, 2024-01-23 at 14:37 +0100, Jan Beulich wrote:
> > > On 23.01.2024 13:34, Oleksii wrote:
> > > > On Tue, 2024-01-23 at 12:14 +0100, Jan Beulich wrote:
> > > > > On 22.12.2023 16:13, Oleksii Kurochko wrote:
> > > > > > --- a/xen/common/Kconfig
> > > > > > +++ b/xen/common/Kconfig
> > > > > > @@ -47,6 +47,9 @@ config ARCH_MAP_DOMAIN_PAGE
> > > > > >  config GENERIC_BUG_FRAME
> > > > > >     bool
> > > > > >  
> > > > > > +config GENERIC_FIND_NEXT_BIT
> > > > > > +   bool
> > > > > 
> > > > > There's no need for this, as ...
> > > > > 
> > > > > > --- a/xen/lib/Makefile
> > > > > > +++ b/xen/lib/Makefile
> > > > > > @@ -3,6 +3,7 @@ obj-$(CONFIG_X86) += x86/
> > > > > >  lib-y += bsearch.o
> > > > > >  lib-y += ctors.o
> > > > > >  lib-y += ctype.o
> > > > > > +lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find-next-bit.o
> > > > > 
> > > > > ... you're moving this to lib/. Or have you encountered any
> > > > > issue
> > > > > with building this uniformly, and you forgot to mention this
> > > > > in
> > > > > the description?
> > > > I didn't check. My intention was to provide opportunity to
> > > > check if
> > > > an
> > > > architecture want to use generic version or not. Otherwise, I
> > > > expected
> > > > that we will have multiple definiotion of the funcion.
> > > > 
> > > > But considering that they are all defined under #ifdef...#endif
> > > > we
> > > > can
> > > > remove the declaration of the config GENERIC_FIND_NEXT_BIT.
> > > 
> > > What #ifdef / #endif would matter here? Whats in lib/ is intended
> > > to
> > > be
> > > generic anyway. And what is in the resulting lib.a won't be used
> > > by
> > > an
> > > arch if it has an arch-specific implementation. Problems could
> > > arise
> > > if
> > > an arch had an inline function colliding with the out-of-line
> > > one.
> > > But
> > > that's about the old case where I could see a need to make the
> > > building
> > > of one of the objects conditional. And you'll note that withing
> > > this
> > > Makefile there are pretty few conditionals.
> > We will have such issue with PPC:
> > ...
> > static inline unsigned long find_next_bit(const unsigned long
> > *addr,
> >                                           unsigned long size,
> >                                           unsigned long offset)
> > ...
> > 
> > It looks like an introduction of new config for find_next_bit is
> > needed.
> > 
> > Does a better option exist? Would making find_next_bit non inline
> > non
> > inline for PPC better?
> 
> Isn't that generic code anyway? If so, that also wants replacing by
> the generic library function(s). Shawn - I have to admit I have a
> hard time seeing why this was introduced as inline functions in the
> first place.
You are right, it is generic one too. I'll replace it too.

~ Oleksii