Re: [PATCH 4/6] bitops: unify non-atomic bitops prototypes across architectures

Alexander Lobakin
2022-06-07T11:03:10Z

From: Yury Norov <yury.norov@gmail.com>
Date: Mon, 6 Jun 2022 13:48:50 -0700

> On Mon, Jun 06, 2022 at 01:49:05PM +0200, Alexander Lobakin wrote:
> > Currently, there is a mess with the prototypes of the non-atomic
> > bitops across the different architectures:
> >
> > ret bool, int, unsigned long
> > nr int, long, unsigned int, unsigned long
> > addr volatile unsigned long *, volatile void *
> >
> > Thankfully, it doesn't provoke any bugs, but can sometimes make
> > the compiler angry when it's not handy at all.
> > Adjust all the prototypes to the following standard:
> >
> > ret bool retval can be only 0 or 1
> > nr unsigned long native; signed makes no sense
> > addr volatile unsigned long * bitmaps are arrays of ulongs
> >
> > Finally, add some static assertions in order to prevent people from
> > making a mess in this room again.
> > I also used the %__always_inline attribute consistently they always
> > get resolved to the actual operations.
> >
> > Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> > Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
> > ---
>
> Reviewed-by: Yury Norov <yury.norov@gmail.com>
>
> [...]
>
> > diff --git a/include/linux/bitops.h b/include/linux/bitops.h
> > index 7aaed501f768..5520ac9b1c24 100644
> > --- a/include/linux/bitops.h
> > +++ b/include/linux/bitops.h
> > @@ -26,12 +26,25 @@ extern unsigned int __sw_hweight16(unsigned int w);
> > extern unsigned int __sw_hweight32(unsigned int w);
> > extern unsigned long __sw_hweight64(__u64 w);
> >
> > +#include <asm-generic/bitops/generic-non-atomic.h>
> > +
> > /*
> > * Include this here because some architectures need generic_ffs/fls in
> > * scope
> > */
> > #include <asm/bitops.h>
> >
> > +/* Check that the bitops prototypes are sane */
> > +#define __check_bitop_pr(name) static_assert(__same_type(name, gen_##name))
> > +__check_bitop_pr(__set_bit);
> > +__check_bitop_pr(__clear_bit);
> > +__check_bitop_pr(__change_bit);
> > +__check_bitop_pr(__test_and_set_bit);
> > +__check_bitop_pr(__test_and_clear_bit);
> > +__check_bitop_pr(__test_and_change_bit);
> > +__check_bitop_pr(test_bit);
> > +#undef __check_bitop_pr
>
> This one is amazing trick! And the series is good overall. Do you want me to
> take it in bitmap tree, when it's ready, or you'll move it somehow else?

Thanks :) Yeah I'm glad we can use __same_type() (->
__builtin_types_compatible_p()) for functions as well, it simplifies
keeping the prototypes unified a lot.

I'm fine with either your bitmap tree or Arnd's asm-generic tree, so
it was my question which I happily forgot to ask: which of those two
is preferred for the series.

>
> Thanks,
> Yury

Thanks,
Olek