From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julia Lawall Subject: Re: [PATCH] checkpatch: Add a --strict test for structs with bool member definitions Date: Sat, 14 Apr 2018 23:19:09 +0200 (CEST) Message-ID: References: <891d4f632fbff5052e11f2d0b6fac35d@codeaurora.org> <20180410123305.GF4082@hirez.programming.kicks-ass.net> <95477c93db187bab6da8a8ba7c57836868446179.camel@perches.com> <20180410143950.4b8526073b4e3e34689f68cb@linux-foundation.org> <20180410150011.df9e036f57b5bcac7ac19686@linux-foundation.org> <20180411081502.GJ4082@hirez.programming.kicks-ass.net> <20180411092959.e666ec443e4d3bb6f43901d7@linux-foundation.org> <1c9f185f6086e9d89659f93720a27b660ee17c13.camel@perches.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Joe Perches Cc: Julia Lawall , Andrew Morton , Peter Zijlstra , "Rafael J. Wysocki" , Andy Whitcroft , yuankuiz@codeaurora.org, Linux PM , "Rafael J. Wysocki" , Frederic Weisbecker , Thomas Gleixner , paulmck@linux.vnet.ibm.com, Ingo Molnar , Len Brown , Linux Kernel Mailing List List-Id: linux-pm@vger.kernel.org On Wed, 11 Apr 2018, Joe Perches wrote: > On Thu, 2018-04-12 at 08:22 +0200, Julia Lawall wrote: > > On Wed, 11 Apr 2018, Joe Perches wrote: > > > On Wed, 2018-04-11 at 09:29 -0700, Andrew Morton wrote: > > > > We already have some 500 bools-in-structs > > > > > > I got at least triple that only in include/ > > > so I expect there are at probably an order > > > of magnitude more than 500 in the kernel. > > > > > > I suppose some cocci script could count the > > > actual number of instances. A regex can not. > > > > I got 12667. > > Could you please post the cocci script? > > > I'm not sure to understand the issue. Will using a bitfield help if there > > are no other bitfields in the structure? > > IMO, not really. > > The primary issue is described by Linus here: > https://lkml.org/lkml/2017/11/21/384 > > I personally do not find a significant issue with > uncontrolled sizes of bool in kernel structs as > all of the kernel structs are transitory and not > written out to storage. > > I suppose bool bitfields are also OK, but for the > RMW required. > > Using unsigned int :1 bitfield instead of bool :1 > has the negative of truncation so that the uint > has to be set with !! instead of a simple assign. At least with gcc 5.4.0, a number of structures become larger with unsigned int :1. bool:1 seems to mostly solve this problem. The structure ichx_desc, defined in drivers/gpio/gpio-ich.c seems to become larger with both approaches. julia