From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751790AbdKUKwx (ORCPT <rfc822;w@1wt.eu>);
        Tue, 21 Nov 2017 05:52:53 -0500
Received: from Galois.linutronix.de ([146.0.238.70]:33866 "EHLO
        Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751429AbdKUKww (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 21 Nov 2017 05:52:52 -0500
Date: Tue, 21 Nov 2017 11:52:37 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Jiri Kosina <jikos@kernel.org>
cc: luca abeni <luca.abeni@santannapisa.it>,
        Peter Zijlstra <peterz@infradead.org>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Juri Lelli <juri.lelli@arm.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        Mike Galbraith <efault@gmx.de>, Steven Rostedt <rostedt@goodmis.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched/deadline: Use bools for the state flags
In-Reply-To: <nycvar.YFH.7.76.1711211142300.11505@cbobk.fhfr.pm>
Message-ID: <alpine.DEB.2.20.1711211151200.1782@nanos>
References: <nycvar.YFH.7.76.1711211142300.11505@cbobk.fhfr.pm>
User-Agent: Alpine 2.20 (DEB 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, 21 Nov 2017, Jiri Kosina wrote:

> From: Jiri Kosina <jkosina@suse.cz>
> 
> Commit
> 
> 	799ba82de01e ("sched/deadline: Use C bitfields for the state flags")
> 
> converted state flags into one-bit signed int. Signed one-bit type can be 
> either 0 or -1, which is going to cause a problem once 1 is assigned to it 
> and then the value later tested against 1.
> 
> The current code is okay, as all the checks are (non-)zero check, but I 
> believe that we'd rather be safe than sorry here; remove the fragility by 
> converting the state flags to bool.
> 
> This also silences annoying sparse complaints about this very issue when 
> compiling any code that includes sched.h.

What's wrong with making these bitfields 'unsigned int' ?

> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index a5dc7c98b0a2..b19fa1b96726 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -473,10 +473,10 @@ struct sched_dl_entity {
>  	 * conditions between the inactive timer handler and the wakeup
>  	 * code.
>  	 */
> -	int				dl_throttled      : 1;
> -	int				dl_boosted        : 1;
> -	int				dl_yielded        : 1;
> -	int				dl_non_contending : 1;
> +	bool				dl_throttled;
> +	bool				dl_boosted;
> +	bool				dl_yielded;
> +	bool				dl_non_contending;

Thanks,

	tglx