linux-kernel - Re: [PATCH] bitops: Add a comment explaining the double underscore macros

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Date: Tue, 11 Jun 2024 13:42:09 -0700
From: Yury Norov <yury.norov@...il.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH] bitops: Add a comment explaining the double underscore
 macros

On Tue, Jun 11, 2024 at 03:38:12PM +0300, Dan Carpenter wrote:
> Linus Walleij pointed out that a new comer might be confused about the
> difference between set_bit() and __set_bit().  Add a comment explaining
> the difference.
> 
> Link: https://lore.kernel.org/all/CACRpkdZFPG_YLici-BmYfk9HZ36f4WavCN3JNotkk8cPgCODCg@mail.gmail.com/
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
> v2: re-word the comment, put it right next to the macros and add a blank
>     line in front of the test_bit() macros so it's not mixed in with the
>     non-atomic macros
> 
>  include/linux/bitops.h | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/include/linux/bitops.h b/include/linux/bitops.h
> index 46d4bdc634c0..ba35bbf07798 100644
> --- a/include/linux/bitops.h
> +++ b/include/linux/bitops.h
> @@ -47,12 +47,17 @@ extern unsigned long __sw_hweight64(__u64 w);
>  	  __builtin_constant_p(*(const unsigned long *)(addr))) ?	\
>  	 const##op(nr, addr) : op(nr, addr))
>  
> +/*
> + * The following macros are non-atomic versions of their non-underscored
> + * counterparts.
> + */
>  #define __set_bit(nr, addr)		bitop(___set_bit, nr, addr)
>  #define __clear_bit(nr, addr)		bitop(___clear_bit, nr, addr)
>  #define __change_bit(nr, addr)		bitop(___change_bit, nr, addr)
>  #define __test_and_set_bit(nr, addr)	bitop(___test_and_set_bit, nr, addr)
>  #define __test_and_clear_bit(nr, addr)	bitop(___test_and_clear_bit, nr, addr)
>  #define __test_and_change_bit(nr, addr)	bitop(___test_and_change_bit, nr, addr)
> +
>  #define test_bit(nr, addr)		bitop(_test_bit, nr, addr)
>  #define test_bit_acquire(nr, addr)	bitop(_test_bit_acquire, nr, addr)
>  
> -- 
> 2.39.2

Applied in bitmap-for-next. For the next time please make the subject
prefix [PATCH v2], then [PATCH v3], and so on. The motivation is to
avoid sending emails with identical subjects as some (not mine) email
clients consider one as a reply to another.

Thanks,
Yury