From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4CE5242E8C8 for ; Thu, 16 Jul 2026 14:35:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784212532; cv=none; b=LWv2Xc1Qkv7cm7KlTnD3qJbrZHCsjxKGUOITzjV0WcP01EN8198QbHrpbqzSxIJr3PUegzdtfcdUpY8bVT1H5rANkOJaqsMaBgq6zFot92JFpTjWKC+/9ubWucABwkt9BDcT15Q5ymkC4+hirzAcyoREfAKcVD7SPGLCgCOtq0U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784212532; c=relaxed/simple; bh=s4Z0Ej/XZ9Mjit+zAgQgiUD53uHWvv4S7S/y1lDBrMo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Mj7eegDK89CjBI9hesZwcwwuIophS0dIstBPGssIuTy3zZal0iP8zEEjlcjQqsSx748Vt6JotLn/84SpSCSSCIBrtRgXuojgmPrdlm1fC6qifUVlA9UwKNpxflNUPG/2oC1iik0wx/lHANKYzsOFRIjZd+WmKtqcm/b+FVe6esE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=YopSsT/o; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="YopSsT/o" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7BAB01F000E9; Thu, 16 Jul 2026 14:35:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784212530; bh=iYH0AyrVv3jiqVmNIPrf/X7bO0FpVvcXVvqbbzKDHYE=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=YopSsT/oAF+qaQItyuURL/zwKl9K2wfEldcV24J40lhNPFmFAgrBL1thGiIs62eOy lzwhtq9RTP1DeCWaDglATxvSWcMj14vDIbVuf0oOx+Lx9Fd5q6h7yaf6tB+LDNVs+n W+Hiq5wwPHLcKXkeGe6jN/VftMe75ZbDJASVqKIM= Date: Thu, 16 Jul 2026 16:09:37 +0200 From: Greg Kroah-Hartman To: Vincent Mailhol Cc: Alexey Dobriyan , Andrew Morton , Rasmus Villemoes , Sakari Ailus , Nick Desaulniers , Alexander Lobakin , Arnd Bergmann , David Sterba , Ivo van Doorn , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] container_of: remove useless pair of parentheses Message-ID: <2026071624-lunar-casually-55fb@gregkh> References: <20260714-containerof_refactor-v1-0-b5c31164d2ad@kernel.org> <20260714-containerof_refactor-v1-2-b5c31164d2ad@kernel.org> <2026071505-fracture-opt-5374@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Jul 15, 2026 at 06:27:31PM +0200, Vincent Mailhol wrote: > On 15/07/2026 at 16:57, Greg Kroah-Hartman wrote: > > On Wed, Jul 15, 2026 at 04:51:28PM +0200, Vincent Mailhol wrote: > >> On 15/07/2026 at 16:30, Alexey Dobriyan wrote: > >>> On Tue, Jul 14, 2026 at 08:18:02PM +0200, Vincent Mailhol wrote: > >>>> The last expression in container_of() doesn't need an extra pair of > >>>> parenthesis. Remove it. > >>>> > >>>> Signed-off-by: Vincent Mailhol > >>>> --- > >>>> include/linux/container_of.h | 2 +- > >>>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>>> > >>>> diff --git a/include/linux/container_of.h b/include/linux/container_of.h > >>>> index 28500a62ab7e..68153170db32 100644 > >>>> --- a/include/linux/container_of.h > >>>> +++ b/include/linux/container_of.h > >>>> @@ -21,7 +21,7 @@ > >>>> static_assert(__same_type(*(ptr), typeof_member(type, member)) || \ > >>>> __same_type(*(ptr), void), \ > >>>> "pointer type mismatch in container_of()"); \ > >>>> - ((type *)(__mptr - offsetof(type, member))); }) > >>>> + (type *)(__mptr - offsetof(type, member)); }) > >>> > >>> container_of_const() has the same problem. > >> > >> Yes. But scoped I my series to the container_of() macro only. > >> > >> I don't plan to send a follow-up patch to remove the other useless > >> parenthesis. The things which really bothered me was the __mptr > >> variable which I removed in patch #3. And with that, I am done with > >> what I wanted to contribute in this file. > >> > >> But you are welcome to do this clean-up if you feel the need for it. > >> > >>> And it should parenthesize first argument to _Generic. > >> > >> Do you mean like this: > >> > >> #define container_of_const(ptr, type, member) \ > >> _Generic((ptr), \ > >> const typeof(*(ptr)) *: ((const type *)container_of(ptr, type, member)),\ > >> default: ((type *)container_of(ptr, type, member)) \ > >> ) > >> > >> ? > >> > >> Why would parenthesis be needed here? I don't see what kind of > >> expression would make the current implementation unsafe. > > > > It took me a while working with container_of_const() to get it right > > with the (), so be careful removing any. > > I just tested this patch: > > ---8<--- > diff --git a/include/linux/container_of.h b/include/linux/container_of.h > index 1f6ebf27d962..03d5b91534a7 100644 > --- a/include/linux/container_of.h > +++ b/include/linux/container_of.h > @@ -34,8 +34,8 @@ > */ > #define container_of_const(ptr, type, member) \ > _Generic(ptr, \ > - const typeof(*(ptr)) *: ((const type *)container_of(ptr, type, member)),\ > - default: ((type *)container_of(ptr, type, member)) \ > + const typeof(*(ptr)) *: (const type *)container_of(ptr, type, member),\ > + default: (type *)container_of(ptr, type, member) \ > ) > #endif /* _LINUX_CONTAINER_OF_H */ > ---8<--- > > I could compile and boot it, no problem (I am actually writing this > message from a machine on which this patch is applied). > > So, yes, I believe that these two pairs of parenthesis can be removed. > Just not sure if it is worth it. For container_of(), the parenthesis > removal was part of a series with more meaningful changes. I don't > feel exited of sending another series to just remove the > container_of_const() parenthesis. Yeah, if it's not hurting anything, let's just leave it as-is for now. thanks, greg k-h