From: Julia Lawall <julia.lawall@lip6.fr>
To: Joe Perches <joe@perches.com>
Cc: 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: Thu, 12 Apr 2018 08:22:12 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.20.1804120816130.3559@hadrien> (raw)
In-Reply-To: <1c9f185f6086e9d89659f93720a27b660ee17c13.camel@perches.com>
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.
>
>
next prev parent reply other threads:[~2018-04-12 6:22 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 [this message]
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
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
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