linux-kernel - Re: [PATCH] omit POSIX timer stuff from task

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Date:   Fri, 20 Jan 2017 14:32:15 -0800
From:   John Stultz <john.stultz@...aro.org>
To:     Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] omit POSIX timer stuff from task_struct when disabled

On Mon, Jan 9, 2017 at 10:49 AM, Nicolas Pitre <nicolas.pitre@...aro.org> wrote:
> When CONFIG_POSIX_TIMERS is disabled, it is preferable to remove related
> structures from struct task_struct and struct signal_struct as they
> won't contain anything useful and shouldn't be relied upon by mistake.
> Code still referencing those structures is also disabled here.
>
> Signed-off-by: Nicolas Pitre <nico@...aro.org>
>
[snip]
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 11c5c8ab82..8e333e55a9 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1309,6 +1309,7 @@ void __cleanup_sighand(struct sighand_struct *sighand)
>   */
>  static void posix_cpu_timers_init_group(struct signal_struct *sig)
>  {
> +#ifdef CONFIG_POSIX_TIMERS
>         unsigned long cpu_limit;
>
>         cpu_limit = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
> @@ -1321,6 +1322,7 @@ static void posix_cpu_timers_init_group(struct signal_struct *sig)
>         INIT_LIST_HEAD(&sig->cpu_timers[0]);
>         INIT_LIST_HEAD(&sig->cpu_timers[1]);
>         INIT_LIST_HEAD(&sig->cpu_timers[2]);
> +#endif
>  }

So apologies for not catching this earlier. I was just queuing this
up, when I noticed the style issue here.

Aren't in-function ifdefs frowned upon? Wouldn't it be better to do:
#ifdef CONFIG_POSIX_TIMERS
static void posix_cpu_timers_init_group(struct signal_struct *sig)
{
...
}
#else
static void posix_cpu_timers_init_group(struct signal_struct *sig) {}
#endif

And similar for most of the ifdef'ed out functions in this patch?

thanks
-john