From: Julia Lawall <julia.lawall@lip6.fr>
To: Joe Perches <joe@perches.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Andy Whitcroft <apw@canonical.com>,
yuankuiz@codeaurora.org, Linux PM <linux-pm@vger.kernel.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Frederic Weisbecker <fweisbec@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
paulmck@linux.vnet.ibm.com, Ingo Molnar <mingo@kernel.org>,
Len Brown <len.brown@intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] checkpatch: Add a --strict test for structs with bool member definitions
Date: Sat, 14 Apr 2018 23:19:09 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.20.1804142315300.2750@hadrien> (raw)
In-Reply-To: <b2087cac13c3a1d01ebe1a17e66351f3777bc397.camel@perches.com>
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
next prev parent reply other threads:[~2018-04-14 21:19 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-10 7:33 Subject: [PATCH] [PATCH] time: tick-sched: use bool for tick_stopped yuankuiz
2018-04-10 7:45 ` yuankuiz
2018-04-10 8:51 ` yuankuiz
2018-04-10 8:54 ` yuankuiz
2018-04-10 7:55 ` Subject: [PATCH] " Thomas Gleixner
2018-04-10 8:12 ` yuankuiz
2018-04-10 8:00 ` Rafael J. Wysocki
2018-04-10 8:15 ` yuankuiz
2018-04-10 9:10 ` Thomas Gleixner
2018-04-10 10:07 ` yuankuiz
2018-04-10 11:06 ` Thomas Gleixner
2018-04-10 14:08 ` yuankuiz
2018-04-10 14:49 ` yuankuiz
2018-04-10 23:09 ` yuankuiz
2018-04-10 23:20 ` yuankuiz
2018-04-20 1:47 ` yuankuiz
2018-04-20 6:44 ` yuankuiz
2018-04-20 19:24 ` Joe Perches
2018-04-25 7:01 ` yuankuiz
2018-04-10 11:26 ` Peter Zijlstra
2018-04-10 12:07 ` Thomas Gleixner
2018-04-10 12:26 ` Peter Zijlstra
2018-04-10 12:33 ` Subject: [PATCH] " Peter Zijlstra
2018-04-10 15:14 ` Joe Perches
2018-04-10 16:30 ` Peter Zijlstra
2018-04-10 15:41 ` [PATCH] checkpatch: whinge about bool bitfields Joe Perches
2018-04-10 18:19 ` [PATCH] checkpatch: Add a --strict test for structs with bool member definitions Joe Perches
2018-04-10 21:39 ` Andrew Morton
2018-04-10 21:53 ` Joe Perches
2018-04-10 22:00 ` Andrew Morton
2018-04-11 8:15 ` Peter Zijlstra
2018-04-11 16:29 ` Andrew Morton
2018-04-11 16:51 ` Joe Perches
2018-04-12 6:22 ` Julia Lawall
2018-04-12 6:42 ` Joe Perches
2018-04-12 7:03 ` Julia Lawall
2018-04-12 8:13 ` Peter Zijlstra
2018-04-14 21:19 ` Julia Lawall [this message]
2018-04-17 9:07 ` yuankuiz
2018-04-18 18:38 ` Joe Perches
2018-04-19 4:40 ` Julia Lawall
2018-04-19 4:51 ` Joe Perches
2018-04-19 5:16 ` Julia Lawall
2018-04-19 6:48 ` yuankuiz
2018-04-19 10:42 ` yuankuiz
2018-04-20 1:31 ` yuankuiz
2018-04-11 17:00 ` Peter Zijlstra
2018-04-12 7:47 ` Ingo Molnar
2018-04-12 8:11 ` Peter Zijlstra
2018-04-12 9:35 ` Andrea Parri
2018-04-12 11:50 ` Peter Zijlstra
2018-04-12 12:01 ` Joe Perches
2018-04-12 12:08 ` Peter Zijlstra
2018-04-12 12:38 ` Joe Perches
2018-04-12 16:47 ` Andrew Morton
2018-04-12 11:52 ` Kalle Valo
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.DEB.2.20.1804142315300.2750@hadrien \
--to=julia.lawall@lip6.fr \
--cc=akpm@linux-foundation.org \
--cc=apw@canonical.com \
--cc=fweisbec@gmail.com \
--cc=joe@perches.com \
--cc=len.brown@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=paulmck@linux.vnet.ibm.com \
--cc=peterz@infradead.org \
--cc=rafael@kernel.org \
--cc=rjw@rjwysocki.net \
--cc=tglx@linutronix.de \
--cc=yuankuiz@codeaurora.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).