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: Thu, 12 Apr 2018 08:22:12 +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: <1c9f185f6086e9d89659f93720a27b660ee17c13.camel@perches.com> Sender: linux-kernel-owner@vger.kernel.org To: Joe Perches Cc: 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: > (Adding Julia Lawall) > > 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. I'm not sure to understand the issue. Will using a bitfield help if there are no other bitfields in the structure? julia > > > and the owners of that code will > > be wondering whether they should change them, and whether they should > > apply those remove-bool-in-struct patches which someone sent them. > > Which is why the warning is --strict only > > > So... can we please get some clarity here? > > > > ... > > > > (ooh, https://lkml.org/lkml/2017/11/21/384 is working this morning) > > > > hm, Linus suggests that instead of using > > > > bool mybool; > > > > we should use > > > > unsigned mybool:1; > > > > However that introduces the risk that alterations of mybool will use > > nonatomic rmw operations. > > > > unsigned myboolA:1; > > unsigned myboolB:1; > > > > so > > > > foo->myboolA = 1; > > > > could scribble on concurrent alterations of foo->myboolB. I think. > > Without barriers, that could happen anyway. > > To me, the biggest problem with conversions > from bool to bitfield is logical. ie: > > unsigned int.singlebitfield = 4; > > is not the same result as > > bool = 4; > > because of implicit truncation vs boolean conversion > so a direct change of bool use in structs to unsigned > would also require logic analysis. > >