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

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Date:   Mon, 6 Jun 2022 13:48:50 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Alexander Lobakin <alexandr.lobakin@...el.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Richard Henderson <rth@...ddle.net>,
        Matt Turner <mattst88@...il.com>,
        Brian Cain <bcain@...cinc.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        "David S. Miller" <davem@...emloft.net>,
        Kees Cook <keescook@...omium.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Marco Elver <elver@...gle.com>, Borislav Petkov <bp@...e.de>,
        Tony Luck <tony.luck@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-alpha@...r.kernel.org, linux-hexagon@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-m68k@...ts.linux-m68k.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/6] bitops: unify non-atomic bitops prototypes across
 architectures

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@...ux.intel.com>
> Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>
> ---

Reviewed-by: Yury Norov <yury.norov@...il.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,
Yury