linux-kernel - Re: [PATCH] sched/deadline: Use bools for the state flags

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Message-ID: <alpine.DEB.2.20.1711211151200.1782@nanos>
Date:   Tue, 21 Nov 2017 11:52:37 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jiri Kosina <jikos@...nel.org>
cc:     luca abeni <luca.abeni@...tannapisa.it>,
        Peter Zijlstra <peterz@...radead.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Juri Lelli <juri.lelli@....com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mike Galbraith <efault@....de>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/deadline: Use bools for the state flags

On Tue, 21 Nov 2017, Jiri Kosina wrote:

> From: Jiri Kosina <jkosina@...e.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